Graduate Student Seminar Homepage | Department of Physics | University of Miami

Graduate Student Seminars

Open All Tabs
  • Graduate Student Seminar 2025

    The oral communications course (Graduate Student Seminar) for first-year, second-year and third-year physics graduate students is meeting this year once a week, on Fridays 2:30 - 3:45 p.m. in Room 105 of the Knight Physics Building, and is being led by Prof. Rafael Nepomechie.

    The main idea is for students to gain practice in planning and presenting a talk. Each speaker is given either 20 minutes (second-year students) or 30 minutes (third-year students), with up to 10 additional minutes for questions/answers. The talks should be accessible to an advanced undergraduate student. In other words, speakers should not assume that their audience has any specialized knowledge about their topic.

    The talks are open to the entire Physics family (undergraduate and graduate students, postdocs, and faculty). The audience provides feedback after each talk.

    Schedule and preliminary talk titles and abstracts:

    • Jan 17
      • Choosing topic, title and abstract
    • Jan 24
      • How to give a good talk
    • Jan 31
      • Speaker: Shahnoor Rahman
      • Title: A novel thermoelectric generator without semiconductors
      • Abstract: Lithium purple bronze(LiPB), Li0.6 Mo6 O17, is a single-phase material that behaves above 300K like an n-type metal along its quasi-one-dimensional chains (b axis) and a p-type semiconductor along the mutually perpendicular c axis. The significant difference in thermopowers* Sc - Sb ≈ 200 μ V/K along c and b makes it a thermoelectric generator. Transverse Peltier thermopower, and power generation measurements on a series of single-crystal specimens cut with their body axes at various angles with respect to the chain direction in the temperature range 300K ≤ T ≤ 500K will be discussed. * J. L. Cohn et al., Phys. Rev. Lett. 112, 186602 (2014).
    • Feb 7
      • Speaker: Zichao Liu
      • Title: An exploration into Drosophila sleep
      • Abstract: Sleep is an important and complex process in the biological world. It happens every day, but its mechanistic underpinnings remain unclear. Two neuronal systems are thought to be the main regulators of the sleep --- the circadian clock system, responsible for the daily rhythm of the sleep and the homeostatic control system, maintaining the balance of the sleep amount. Here we use Drosophila melanogaster as an experimental model to study two questions in the regulation of sleep. Firstly, by doing sleep deprivation experiments we study the integration time of Drosophila homeostatic control system. Secondly, by applying hidden Markov model we explore the relationships of the sleep regulators at a systems level.
    • Feb 14
      • Speaker: Mehrdad Shiri
      • Title: Ultra-long range charge transport in the open-shell diradical molecules
      • Abstract: A grand challenge in molecular electronics is the development of molecular materials that can facilitate efficient long-range charge transport. Research spanning more than two decades has been fueled by the prospects of creating a new generation of miniaturized electronic technologies based on molecules whose synthetic tunability offers tailored electronic properties and functions unattainable with conventional electronic materials. Integrating such materials with solid-state nanodevices promises revolutionary advancements spanning diverse fields, including electronics, sensing, energy conversion, spintronics, and quantum information science. However, despite the exploration of a vast chemical space, current design paradigms produce molecules that exhibit off-resonant transport in the low-bias regime. This feature, inherent to almost all molecules, limits the conductance of a molecular backbone to unsatisfactorily low levels - several orders of magnitude below the conductance quantum 1G0 - and often results in an exponential decay in conductance with increasing length. The main objective of this research is to achieve long-sought-after quasi-metallic charge transport in robust and air-stable molecular systems and gain a deep understanding of its underlying mechanism.
    • Feb 21
      • Speaker: Joseph Sterling
      • Title: Studying the oldest black holes and galaxies via X-rays with the James Webb Space Telescope
      • Abstract: Our study of Super Massive Black Holes (SMBHs) is tied to the Active Galactic Nuclei (AGNs) which they inhabit. Surveys of the cosmos show that AGNs had already formed much earlier than our current models predict. X-rays emitted by Star Forming Galaxies (SFGs) have been shown to be a robust probe of AGNs. However, current X-ray telescopes, such as Chandra, cannot resolve high redshift (high-z) objects from the x-ray background; depriving us of information to investigate the early universe further. With James Webb Space Telescope's (JWST's) outstanding capability to probe earlier into the universe than ever before, albeit with infrared, we now have access to a new slew of high-z AGN candidates to investigate. By combining both, we can probe the early Universe using stacking analysis. This will give us insight into star formation, SMBH growth, and AGN density of the early universe.
    • Feb 28
      • Speaker: Haixin Zhang
      • Title: Exploring the nexus of electrical and mechanical properties of biomolecules at the single-molecule level
      • Abstract: Investigating the mechanical and electrical properties of materials at the single-molecule level is of great significance because it reveals fundamental molecular behaviors. However, current single-molecule technologies face formidable challenges in simultaneously probing electrical and mechanical information in a single measurement. This limitation hinders a comprehensive understanding of intrinsic material properties and the correlation between different properties due to the lack of real-time multidimensional observations. The primary topic of this talk is to develop a comprehensive single-molecule experimental approach based on the conductive atomic force microscopy break junction (CAFM-BJ) technique to uncover the interplay of force-conductance (F-G) properties in molecular-scale materials and systems. From the experimental findings, the project seeks to reveal molecular-level mechanisms of charge transport and bonding, advancing applications in biosensing, nanobiotechnology, and molecular electronics
    • Mar 7
      • Speaker: Homa Saadatmand
      • Title: Optical thermodynamics: exploring nonlinear dynamics in multimode systems
      • Abstract: Understanding the thermodynamic principles in optical systems provides a unique lens through which complex nonlinear interactions can be analyzed. This presentation explores the thermodynamic behavior of highly multimode nonlinear optical systems, focusing on the emergence of equilibrium states defined by unique optical temperatures and chemical potentials. Beginning with an introduction to multimode photonic systems and their applications, we delve into the conditions leading to thermalization in these arrangements. Using statistical mechanics, we discuss how power distribution among modes can be characterized by Rayleigh-Jeans statistics and how transitions between positive and negative optical temperatures occur.
    • Mar 21
      • Speaker 1: Jack Hu
      • Title: Transformer: the foundation of ChatGPT et al.
      • Abstract: Over the last ten years, Artificial Intelligence (AI) has taken the world by storm. From OpenAI's ChatGPT to Huawei's smart, AI-powered self-driving SUVs, this new breed of technology has infiltrated every aspect of our lives and inevitably changed many ways we interact with the world. While AI's potential remains substantial, the lack of understanding of this technology by its users has become more and more evident. To demystify and recognize what AI can or can't do, we need to examine its foundation: the Transformer. By making sense of what goes on inside the black box of AI, we can become more effective users of this technology and truly release its potential.

      • Speaker 2: Alberto Magaraggia
      • Title: Exploring the early universe: what links the infrared and X-ray backgrounds?
      • Abstract: The sum of all contributions to the electromagnetic radiation emitted in the universe is called "Cosmic Background Radiation". The cross-correlation between the Cosmic Infrared Background (CIB) and the Cosmic X-ray Background (CXB) fluctuations reveals important information about distant populations contributing to the components of these backgrounds. By utilizing infrared maps from the Spitzer telescope and X-ray observations from the Chandra X-ray Observatory, a significant level of correlation has been detected between the CIB and CXB on large angular scales. In this presentation, we will address the implications of the detected correlation between the CIB and CXB, exploring its connection to distant populations of black holes and stars. Future progress in CIB-CXB cross-correlation studies will benefit significantly from the new-generation telescopes such as Euclid and eROSITA.
    • Mar 28
      • Speaker: Galib Hoq
      • Title: Path integrals or how to sum over histories
      • Abstract: The path integral formulation of quantum mechanics was first thoroughly developed by Richard Feynman, building on a line of thought by Dirac. Subsequently, it came to have a great influence in quantum field theory and many other branches of physics. Not only is this formulation of quantum theory very intuitively appealing, but it also provides enormous theoretical and computational power for physicists to tackle difficult problems. We will give a brief overview of the ideas behind the path integral and delve into some interesting applications of it in areas such as particle physics, statistical mechanics, and condensed matter.
    • Apr 4
      • Speaker 1: Russell Roberts
      • Title: Attributes of X-ray lens design
      • Abstract: From broken bones to black holes, the imaging capabilities of X-rays have been instrumental in understanding a broad range of physical phenomena. In the realm of soft X-ray astronomy, focusing these photons presents a unique challenge due to their short wavelengths and low reflectivity. This presentation explores the mechanisms behind X-ray lens design and the principles that allow us to capture these high-energy photons. We will introduce and compare the three major optical designs used in soft X-ray astronomy: Kirkpatrick-Baez (K-B), Wolter, and Lobster-Eye optics. Each design employs distinct geometries to achieve focus, with specific advantages and limitations for various observational applications. The talk will provide an overview of the physics behind each optical approach, limitations on implementations, and how these lenses are used in today's X-ray telescopes.

      • Speaker 2: Samuel Mason
      • Title: Shedding light on the universe: an introduction to line intensity mapping
      • Abstract: Line intensity mapping (LIM) represents a novel approach to observing the cosmos, offering insights into the large-scale structure of the universe and the processes driving galaxy formation and evolution. By capturing the integrated emission from unresolved sources, LIM enables us to explore extensive cosmic volumes using distinct spectral lines like CO, Lyman-alpha, and [CII]. Here, I will introduce the fundamental concepts of LIM, including its methodology, instrumentation, and the key astrophysical and cosmological questions it aims to address. We will explore how LIM complements traditional galaxy surveys and its potential to constrain dark matter, dark energy, and the epoch of reionization. Moreover, the discussion will spotlight ongoing and forthcoming LIM initiatives, such as COMAP and SPHEREx, while addressing the hurdles and prospects within this swiftly evolving domain.
    • Apr 11
      • Speaker: Sagarika Bhagade
      • Title: Quasi-1-D Niobium chalcogenides
      • Abstract: Triniobium tetrasulphide (Nb3S4) and Diniobium triselenide (Nb2Se3) are interesting materials for the investigation of novel transport phenomena, primarily due to their quasi-one-dimensional (q1D) nature. In q1D systems, electron-electron interactions become more prominent because of the restricted spatial dimensions. This is different from what we see in higher-dimensional systems where screening effects are more effective at mitigating such interactions. The transport properties of Nb3S4 and Nb2Se3 remain largely unexplored. This gap in research presents an exciting opportunity for further studies to shed light on the interplay between its electronic structure and transport characteristics.
    • Apr 18
      • Speaker 1: Kayla Spencer
      • Title: A new vision in X-ray astronomy: the Lobster-eye Telescope (LXT)
      • Abstract: Micro-pore Optics (MPO), also known as Lobster-eye Optics, address the need for a large field of view in X-ray instruments. When integrated with large area CCDs, the resulting telescope exhibits good angular and energy resolution across a wide energy spectrum. The short focal length inherent to MPOs enables the construction of lightweight telescopes with minimal moment of inertia, facilitating rapid repointing capabilities. The primary mission of the Lobster X-ray Telescope (LXT) is to observe key astronomical features such as the Local Hot Bubble, the Galactic Halo, and the Cygnus Loop, all free from contamination by solar wind charge exchange (SWCX).

      • Speaker 2: Shreenath Guard
      • Title: Randomness in fruit fly sleep
      • Abstract: Most organisms spend a large portion of their lives asleep, though little is known about the mechanisms that control this behaviour. Fruit fly sleep, unlike human sleep, is highly fragmented and stochastic; therefore a complete description of such behaviour must involve the use of stochastic differential equations where the amount of sleep during each sleep event is given by the solution of the modeling equation. To this objective, the simple stochastic process of Orstein and Uhlenbeck is suitable for modeling of sleep duration over a completely stochastic brownian motion process because of the mean reversion displayed in the duration of sleep. Moreover, this description of sleep can capture the dynamics of a range of fruit fly sleep and clock mutants through the parameters of the process such as the long term mean, mean reverting rate and volatility.
    • Apr 25
      • Speaker: Oshani Fernando
      • Title: Drosophila larval temperature-seeking behavior is modified by salt
      • Abstract: Navigating an environment of temporally and spatially varying stimuli is an important behavior for survival for all motile organisms. The Drosophila larva, an organism with relatively simple brain circuitry, has a robust, quantifiable navigational response to many stimuli, especially temperature. Larvae navigate away from both too-cold and too-warm temperatures. Neurons in the peripheral nervous system strongly respond even to very small decreases and increases in temperature. In the absence of negative or positive stimuli, larvae explore their environment in a random walk pattern, and respond to sensory stimuli by modulating random walk parameters, particularly turning rate. Previous research has found that larvae normally do not navigate in a 21-270C temperature gradient, but crawl towards the cold on a substrate containing salt, NaCl. We probe whether the salt-sensing taste receptor, Gr66a, which may also play a role in temperature sensing, is responsible for this valence change, using a combination of behavioral and neurophysiological experiments. We quantify neural responses to temperature in the Gr66a receptor using reverse correlation, and measure the Gr66a receptor's responses to variations in temperature in the presence of salt.
    • May 2
      • Speaker 1: Umasree Thekkemadam
      • Title: Intermediate-mass black holes in dwarf galaxies
      • Abstract: Black holes (BHs) are astronomical objects with intense gravity, classified based on their mass (MBH ) into stellar black holes (MBH ≤ 102), intermediate-mass black holes (IMBHs; MBH ≈ 102 - 106), and supermassive black holes (SMBHs; MBH ≥ 106 ). A fundamental question in astronomy is how small stellar black holes evolve into the giant supermassive black holes observed in the most massive galaxies, given the limited accretion time. IMBHs are proposed as the missing evolutionary link between stellar and supermassive black holes, hosting black hole seeds formed in the early Universe and potentially residing in dwarf galaxies. To investigate their presence, X-ray observations of accretion signatures serve as a valuable probe, particularly for IMBHs with lower Eddington ratios. This study utilizes Chandra X-ray observations to detect IMBHs in Milky Way satellite dwarf galaxies, addressing their role in bridging the gap between the formation and evolution of supermassive black holes.

      • Speaker 2: Gopika Madhu
      • Title: Quantifying ductile-brittle deformations in a novel epithelial system
      • Abstract: Epithelial tissues play a vital role in providing protection and other essential biological functions. Despite being ubiquitous in the animal kingdom, our current understanding of the mechanics of epithelial tissues is still very limited. This work focuses on measuring material responses such as local stresses and strains within the cellular monolayers as they undergo ductile to brittle deformations. These rapid tissue deformations that have been observed in the marine organism Trichoplax adhaerens and are further investigated using Traction Force Microscopy (TFM). Preliminary results show that these animals generate tractions as small as a few Pascals. Quantitative kinematics experiments and a simple ball-spring model developed previously, to understand the transition from ductile to brittle properties in these tissues, indicate this transition is to be purely force driven. This study involves projects on three fronts: kinematic characterization using Particle Imaging Velocimetry, traction measurements using TFM, and localized yield force measurements using soft lithography during ductile-brittle tissue deformations. The projects are expected to contribute to building a size-dependent framework that governs ductility vs. brittleness in monolayer epithelial tissues.

     

  • Graduate Student Seminar 2024

    N/A

  • Graduate Student Seminar 2023

    The oral communications course (Graduate Student Seminar) for second-year and third-year physics graduate students meets once a week, on Fridays 4:00 - 5:00 p.m. in Room 105, and is led by Prof. Rafael Nepomechie.

    The main idea is for students to gain practice in planning and presenting a talk. Each speaker is given either 20 minutes (second-year students) or 30 minutes (third-year students), with up to 15 additional minutes for questions/answers. The talks should be understandable to an advanced undergraduate student. In other words, speakers should not assume that their audience has any specialized knowledge about their topic.

    The talks are open to the entire Physics family (undergraduate and graduate students, postdocs, and faculty). Each talk is followed by a discussion based in part on the anonymous feedback provided by an audience survey with these questions.

    Schedule and preliminary talk titles and abstracts:

    • Feb 3
      • Choosing topic, title and abstract
    • Feb 10
      • Presentations of preliminary titles and abstracts
    • Feb 17
      • How to give a good talk
    • Feb 24
      • Speaker: Rafael Nepomechie
      • Title: Exactly solvable models
      • Exactly solvable models, such as the 2-body problem and the hydrogen atom, have served as important signposts guiding our understanding of the physical world. I will briefly describe two other famous examples: the Heisenberg spin chain and the so-called AdS/CFT correspondence.
    • Mar 3
      • Speaker: Shubham Sinha
      • Title: Cell flows in a developing chick embryo
      • Abstract: The bilateral cell flows during the early-stage development of chick embryos are accompanied by the formation of a longitudinal midline structure known as the primitive streak. The exact physical mechanism of formation of the primitive streak and its correlation with cell flows is still unclear. I will briefly describe the cell flow quantifications such as speed, vorticity, flows axis and asymmetry in such flows.
    • Mar 10
      • Speaker: No talk
      • Title:
      • Abstract:
    • Mar 24
      • Speaker: Gaurav Verma
      • Title: Gauge theory of superstrings
      • Abstract: Gauge theories present themselves with symmetries that are for the most part generated by specific category of constraints. The attempts to eliminate pure gauge variables by gauge fixing leads to loss of covariance. In my talk I present simple gauge theories leading up to superstring and address ways to get covariant description.
    • Mar 31
      • Speaker: Zikun Cao
      • Title: Fabrication of high efficiency perovskite solar cells
      • Abstract: Brief history and situation of solar energy and perovskite solar cells (PSC); Fabrication of PSC (Composition, Device structure, Deposition method); Characterization method of perovskite and PSC: Xrd, TA, PL
    • Apr 7
      • Speaker: Jose Adorno
      • Title: 3D Simulations of Blast waves from Supernova Explosions
      • Abstract: The sudden release of energy resulting from a supernova explosion produces a blast wave through the surrounding medium. Using the multipurpose hydrodynamic code Arepo, we can follow the evolution of the blast wave and its impact on the surrounding medium. In this talk I will present results from 3D supercomputer simulations and compare them to the analytic solutions of the Sedov-Taylor point explosion problem.
    • Apr 14
      • Speaker: Christian van der Merwe
      • Title: 3D Simulations of Stellar Collisions
      • Abstract: Environments of high stellar density create a promising stage for collisions between a wide variety of stars. Some of these collisions, such as one between a white dwarf and a main-sequence star, might be energetic enough to be detected by our newest observational facilities. These instruments will be able to detect millions of different exotic astronomical events in the night sky, and thus we need a way to differentiate these collisions from other events that will be detected. Using 3D hydrodynamic simulations, this work aims to make predictions for the energetics, chemical signatures, and morphology of collisions between white dwarfs and main-sequence stars. In this talk, I will describe the physics and numerical methods we use to model these collisions and the results that have been obtained so far.
    • Apr 21
      • Speaker: Sushil Pokharel
      • Title: Photon orbital angular momentum in communication
      • Abstract: Electromagnetic radiation has a broad range spectrum from low-energy radio waves to high-energy gamma rays respectively in which light occupies a rather small range (from 400 nm to 700 nm in wavelength) that can be detected by the human eye. The study of light interaction with matter not only uncovers the hidden secrets of the Universe but also provides vital information about various systems through which it propagates. Also, it can carry much more information and transmit at much faster rate compare to ordinary radio-wave. The major problem with using light as a source of communication is scattering and interference due to the inconsistency in the refractive indices at different points in space and time. However, recent studies in the field of statistical optics suggested that structured light, for instance, light carrying orbital angular momentum (OAM) can be highly useful for data communication and many other fields because of its unique properties like twisted helical phase front, orthogonality between different OAM modes, etc.
    • Apr 28
      • Speaker: Kavon Bastian
      • Title: Exploring the world of Optical Turbulence in Imaging
      • Abstract: Optical turbulence is a microscale phenomenon that acts on light waves travelling through a media. Tiny refractive index fluctuations distort the path of the light beam. It can be used to model image blurring [in the atmosphere, ocean and biological tissues]. Fourier techniques can be used to detect precancerous cells

    Preparing for your presentation

    Giving a presentation (Beardon)

    Suggestions for giving talks (Geroch)

  • Graduate Student Seminar 2022

    N/A

  • Graduate Student Seminar 2021

    The oral communications course (Graduate Student Seminar) for second-year and third-year physics graduate students meets once a week, on Fridays 4:00 - 5:00 p.m., this year remotely via Zoom, and is led by Prof. Rafael Nepomechie.
    The main idea is for students to gain practice in planning and presenting a talk. Each speaker is given either 20 minutes (second-year students) or 30 minutes (third-year students), with up to 15 additional minutes for questions/answers. The talks should be understandable to an advanced undergraduate student. In other words, speakers should not assume that their audience has any specialized knowledge about their topic.
    The talks are open to the entire Physics family (undergraduate and graduate students, postdocs, and faculty). If you do not receive a Zoom invitation, please do not hesitate to request one from nepomechie at miami.edu. Each talk is followed by a discussion based in part on the anonymous feedback provided by an audience survey with these questions.
    Schedule and preliminary talk titles:
    • Feb 5
      • Choosing topic, title and abstract
    • Feb 12
      • Presentations of preliminary titles and abstracts
    • Feb 19
      • How to give a good talk
    • Feb 26
      • Speaker: Rafael Nepomechie
      • Title: Exactly solvable models
      • Exactly solvable models, such as the 2-body problem and the hydrogen atom, have served as important signposts guiding our understanding of the physical world. I will briefly describe two other famous examples: the Heisenberg spin chain and the AdS/CFT correspondence.
    • Mar 5
      • Speaker: Dominic Sicilian
      • Title: Measuring distance to supermassive black holes
      • Abstract: There is a monster lurking at the center of nearly every galaxy - a Supermassive Black Hole. These colossal objects can devour vast amounts of matter, converting the mass around them into highly luminous light in a process known as accretion, earning them the name Active Galactic Nuclei (AGN). In spite of their remarkable light output, which exceeds that of all non-explosive classes of objects in the Universe, many AGN become "obscured" to our observing instruments engulfed in intricate structures, byproducts of their large-scale mass consumption. Measuring the distance to a faraway obscured AGN - a feat astronomers accomplish for an extragalactic object by finding its cosmological redshift - is a daunting task. Here, I will discuss the fundamentals of AGN and present ongoing research into a recently developed method of computing obscured AGN redshifts using X-ray spectra.
    • Mar 12
      • Speaker: Bikram Shrestha
      • Title: Quantitative analysis of fluid flow created by Ctenophores
      • Abstract: Ctenophores (comb jellies) are known to be the largest animals that use cilia for feeding and swimming. They are very efficient at prey capturing even though they do not have highly developed nervous systems. Here I discuss the bio-physical behavior of these organisms, focusing on ciliary movements and fluid flow. For the quantification of flow the field, I use 2D Particle Image Velocimetry (PIV) as a tool.
    • Mar 19
      • Speaker: E. Riley Blocker
      • Title: Ocean optics - seeing the blue
      • Abstract: In ocean remote sensing, satellites in orbit above Earth's atmosphere image our oceans. The signal received by the satellite's cameras contain information about the sunlight that was scattered upward toward the sensor by ocean water. Thus, this data leads to global insight into what particles and marine life are in the ocean. However, because this signal must traverse the Earth's atmosphere to reach the satellite, the signal becomes contaminated with atmospheric processes. This issue highlights the need for an in water instrument that, by virtue of its location, will not have to "worry" about the atmospheric signal. I've designed and built an optical oceanographic instrument, named PixPol, to locally measure the light leaving the ocean's surface.
    • Mar 26
      • Speaker: Debasish Sarker
      • Title: Modeling children's movement in classroom
      • In this presentation, I will investigate the spatial structure of children's social interactions in classrooms. Real-time location and orientation were continuously recorded in three classes of a local elementary school by using Radiofrequency Identification (RFID. To explain our findings from the experiment, I will propose a dynamical model that integrates the orientational interaction with spatial movements. Then I will analyze the statistical physics of the proposed model and explain the rules of different thermodynamical quantities. And finally, I will discuss the feasibility of numerical simulation for the proposed model to match the empirical results.
    • Apr 2
      • Speaker: Roberto Moncada
      • Title: A rocket mission to resolve a a nagging problem in X-ray astronomy
      • Abstract: The Diffuse X-rays from the Local Galaxy (DXL) sounding rocket mission, launching in December 2021, will detect X-rays coming from within the solar system, distant galaxies, and everywhere in between. The goal is to disentangle X-rays originating from solar interactions with the interplanetary and geocoronal medium, a remnant explosion that our solar system has found itself in, and hot gas surrounding our galaxy and others. The detector has a simple design, used since the 1970s, that is basically high voltage wires within a volume of gas . In this presentation, I will illustrate how the DXL detector works and how it will make a critical measurement that has implications for the rest of X-ray astronomy.
    • Apr 9
      • Speaker: Alessandro Peca
      • Title: How to see a super massive black hole

      • Abstract: Super massive black holes are black holes with huge masses, up to billions of times the Sun's mass, located at the center of every galaxy. When they are able to accrete their mass attracting the surrounding material, they become "active" producing radiation over the full electromagnetic spectrum. Because their emission may dominate the starlight coming from the host galaxy, these objects are called active galactic nuclei (AGN).

        In this presentation, I will describe the AGN structure and the physical processes involved in the AGN activity. Furthermore, I will discuss the main features that let researchers identify and characterise AGN from the radio to the X-ray wavelengths.

    • Apr 16
      • Speaker: Arnaldo Aguero
      • Title: The almost gravity of a tube
      • Abstract: General Relativity is a famous and wildly successful model of the universe that describes gravity as a result of the curvature of spacetime due to the presence of matter, or more precisely energy. When this model is applied to a tube, a structure consisting of a lower dimensional slice of space and all points less than some fixed distance from that slice, a gravity like phenomena emerges purely from the geometric properties of the tube. Here I will discuss the derivation of the key result. I will also briefly go over applications to topological defects such as cosmic strings, and some results in 1+1 de Sitter space.
    • Apr 23
      • Speaker: Giulia Cerini
      • Title: Statistical methods for probing cluster astrophysics
      • Many branches of physics and engineering have extensively used correlations and power spectra to find repeating patterns in a wide range of signals and images. In astrophysics this technique has been utilized for several purposes, including the analysis of X-ray images of galaxy clusters to study the spatial distribution of the hot gas responsible for the emission. This analysis allows to infer information on a variety of physical processes. My research aims to probe the complex physics of galaxy cluster dynamics, correlating the X-ray emitting hot gas with the mass distribution, dominated by dark matter, assessing if these two components trace each other.
    • Apr 30
      • Speaker: Moslem Mahdavifar
      • Title: Is it possible to test Bell inequality with continuous wave lasers?
      • Abstract: Initially proposed as an approach to test the EPR paper, the Bell inequality faced some experimental obstacles. First, physicists must have the schemes of testing this inequality in Lab. Providing experimental setup for such schemes was the next challenge. At the end of 1960's a group of physicists revised the inequality for the experimental test with the polarization state of light and then through so called some generations of experiments physics community try to show the position of Bell inequality. All these generations have examined the idea with the nonlinear optics as a source of Bell State which has some difficulties such as low intensity of photons due to low efficiency of non-linearity. However, recently an idea was introduced to do quantum optics phenomena with CW sources, and there have been some works in this direction which have approved the idea. Here, we want to talk about the possibility of testing Bell inequality with CW sources.

     

    Preparing for your presentation

    Giving a presentation (Beardon)

    Suggestions for giving talks (Geroch)

  • Graduate Student Seminar 2020

    The oral communications course (Graduate Student Seminar) for second-year and third-year physics graduate students meets once a week, on Fridays 4:00 - 5:00 p.m., in Room 105, and is led by Prof. Rafael Nepomechie.

    The main idea is for students to gain practice in planning and presenting a talk. Each speaker is given either 20 minutes (second-year students) or 30 minutes (third-year students), with up to 15 additional minutes for questions/answers. The talks should be understandable to an advanced undergraduate student. In other words, speakers should not assume that their audience has any specialized knowledge about their topic.

    The talks are open to the entire Physics family (undergraduate and graduate students, postdocs, and faculty). Each talk is followed by a discussion based in part on the anonymous feedback provided by the audience using this evalutation form.

    Schedule and preliminary talk titles:

    • Jan 24
      • Choosing topic, title and abstract
    • Jan 31
      • Student presentations of titles and abstracts
    • Feb 7
      • How to give a good talk
    • Feb 14
      • Speaker: Rafael Nepomechie
      • Title: Exactly solvable models
      • Abstract: Exactly solvable models, such as the 2-body problem and the hydrogen atom, have served as important signposts guiding our understanding of the physical world. I will briefly describe two other examples: the Heisenberg spin chain and the AdS/CFT correspondence.
    • Feb 21
      • No seminar
      •  
      •  
    • Feb 28
      • Speaker: Dominic Sicilian
      • Title: Dark Matter Discovered?
      • Abstract: Dark Matter, the undiscovered material accounting for ~85% of mass in the Universe, is among the biggest mysteries in science. A possible explanation lies in a proposed extension to the Standard Model: the Sterile Neutrino. This hypothetical particle could offer explanations for the recently-discovered nonzero neutrino mass, as well as neutrino oscillation, and makes an appealing Dark Matter candidate. In addition, the decay of Sterile Neutrino Dark Matter would emit a photon, thought to be detectable by current X-ray telescopes. In fact, since 2014, various detections of an unidentified emission line at ~3.5 keV have sparked interest and discussion about whether the signature of Sterile Neutrino Dark Matter has been discovered. I will briefly describe the physics of the Sterile Neutrino and its possible status as a Dark Matter particle.
    • Mar 6
      • Speaker: Shengda Huang
      • Title: Does Social Media Make Us Diverse?
      • Abstract: Social media have become an significant feature of modern life. In this internet-based paradise, people from all over the world can talk about their fields of interest, big events just happen or what they have for lunch. It seems that we are all brought closer, thanks to blogs, facebook, twitter and so on. Or is it? Speaker will introduce some interesting facts about how social media change the opinions of societies and introduce a possible model which may give us an explanation.
    • Mar 20
      • Speaker: Pramod Baral
      • Title: Perovskite Single Crystals: A good candidate of Photodetector
      • Abstract: Perovskite materials (ABX3 structure materials) have a vast application in opto-electronic field. Single crystals made from perovskite materials are most useful for photodetector because single crystal has less defect. I will discuss more about how using perovskite single crystals is a good idea while fabricating photodetector.
    • Mar 27
      • Speaker: Roberto Moncada
      • Title: All diffuse low-energy x-ray observations of the universe are contaminated
      • Abstract: Studying the universe with x-rays is difficult due to their interactive nature. The energy scale of these photons (between 0.25 and 1.5 KeV) makes the atmosphere opaque to x-rays, requiring detectors to be launched above this obstacle. The first observations of the x-ray sky by Riccardo Giaconni in 1962 revealed diffuse emission emanating from all directions. Later more sensitive observations made by the ROentgen SATellite (ROSAT) in 1997 showed that there was a temporal variation to the emission. In this talk, I will explore the different components of the so-called Diffuse X-ray Background (DXB) and demonstrate our lab’s effort to disentangle and model them, which would then be used as corrections in future and past studies of diffuse x-ray emission.
    • Apr 3
      • Speaker: Xinwen Zhang
      • Title: Perovskite LEDs
      • Abstract: Recently, halide Perovskite materials with the general formula ABX3 have undergone remarkable development owing to their outstanding optical and electrical properties, such as long free-carrier diffusion length, higher charge-carrier mobility, tunable bandgap and high photoluminescence quantum yield. In addition, halide Perovskite light emitting diodes also show unprecedented performance with maximum luminance values of up to 91000cm-2. More interestingly, the emission color of halide Perovskite LEDs can also be easily tuned from Cl- to Br-, or I-, making these potential materials for use in white-color-emission properties of halide Perovskite materials.
    • Apr 10
      • Speaker: Kunal Tamang
      • Title: Citation Analysis and Modeling
      • Abstract: Citation distributions are crucial for the analysis and modeling of the activity of scientists. We look for the type of function that best describe the observed citation distributions by investigating the bibliometric data of papers published in journals of American Physical Society. We seek models that can account for the observed diversity in citation dynamics, fit citation histories and predict future citations.
    • Apr 17
      • Speaker: Sicong Huang
      • Title: The Story of the Diffuse X-ray Background
      • Abstract: The diffuse X-ray background (DXB) was first discovered in 1962. Since then, tremendous funds and efforts have been put into the study of DXB, which can help us understand some big astronomical problems, such as the structure, origin, and composition of the universe. In this talk, I willl introduce the DXB, and discuss how it is studied, including how data from the universe in the X-ray domain is obtained, and how this data is analyzed. I will also present an example of my work in the Chandra Deep Field South field, which is one of the deepest multi-wavelength observation fields covering 440 square arcminutes. This will provide some insight into the current situation in DXB research.
    • Apr 24
      • Speaker: Yi Zhang
      • Title: Communication between children without speaking language
      • Abstract: Language is most common tool used in human society to communicate with others. However, the question is that is it the only method for people's communication? The answer is obviously not. Besides specific language, like English, Mandarin, there are many other ways for people to exchange their ideas or do interactions. For instance, different distance between to children indicates different communicating conditions to some extent. In addition, relative angles of two children also represent different relationship and interaction. So is there any way to analyze those non-language communications? That what I will discuss in this presentation.

    Preparing for your presentation

    Giving a presentation (Beardon)

    Suggestions for giving talks (Geroch)

  • Graduate Student Seminar 2019

    The oral communications course (Graduate Student Seminar) for second-year and third-year physics graduate students meets once a week, on Fridays 11:00 a.m. - 12:00 noon, in Room 105, and is led by Prof. Rafael Nepomechie.

    The main idea is for students to gain practice in planning and presenting a talk. Each speaker is given either 20 minutes (second-year students) or 30 minutes (third-year students), with up to 15 additional minutes for questions/answers. The talks should be understandable to an advanced undergraduate student. In other words, speakers should not assume that their audience has any specialized knowledge about their topic.

    The talks are open to the entire Physics family (undergraduate and graduate students, postdocs, and faculty). Each talk is followed by a discussion based in part on the anonymous feedback provided by the audience using this evalutation form.

    Schedule and preliminary talk titles:

    • Jan 25
      • Choosing topic, title and abstract
    • Feb 1
      • Student presentations of titles and abstracts
    • Feb 8
      • How to give a good talk
    • Feb 15
      • Speaker: Rafael Nepomechie
      • Title: Introduction to Quantum Computing
      • Abstract: An international race is currently underway to develop quantum computers and quantum algorithms. In this elementary introduction, we'll address such questions as: What is it? Why is it important? And where are we now?
    • Feb 22
      • Speaker:Yi Zhang
      • Title: Will you still use twitter 10 years from now?
      • Abstract: Like an ecosystem in nature, which has predators and prey living in a relatively stable wild environment, social media has a similar kind of "ecosystem". For instance, twitter is a very popular social media system. Some users prefer "posting" tweets all the time, while others prefer "retweetinng". So is twitter going to survive 10 years later if all the users post tweets day and night? Or retweeting?
    • Mar 1
      • No seminar
      •  
      •  
    • Mar 8
      • Speaker: Kunal Tamang
      • Title: Theory and Application of Complex Networks
      • Abstract: The non-trivial topological characteristics which are not possessed by traditional networks makes complex network a promising research field in today's world. The network of internet, world-wide web, cellular network and citation network are much quoted examples. The evolution from traditional random graph modeling to today's real network model governed by robust organizing principles fascinates to look for wide scope of research in this field. Here, we will discuss with basic idea along with the applications and further promotes some important research topics in the field of complex network.
    • Mar 22
      • Speaker: Xinwen Zhang
      • Title: How to improve the stability of perovskite solar cells
      • Abstract: Perovskite solar cell (PSC) is a kind of solar cell which includes a perovskite structure compound. PSCs have attracted our attention successfully due to their advantages of low processing costs, high conversion efficiency. The efficiency of PSC increases from 3.8% to 23.3% in the past 10 years. Despite the outstanding efficiency, perovskite materials lack long-term stability under ambient operation conditions. However, advancements in compositional engineering have been for several years to improve the ambient stable of PSC.
    • Mar 29
      • Speaker: Pramod Baral
      • Title: Perovskite Solar Cells: A Promising Source of Future Energy
      • Abstract: Organic-inorganic hybrid perovskite material attracts extensive academic attention as perovskite solar cell efficiency has increased to a new record of 22.7% within a few years of research. This material is also applicable in laser, light-emitting device, photo detector, and X-ray detector. Perovskite materials are ABX3 type crystal structure, where A represents organic cation such as Methylammonium (MA), Formamidium (FA) or inorganic cation such as Cesium (Cs), B is Tin (Sn) or Lead (Pb), and X is halide (mainly Iodine and Bromine). Methylammonium or formamidium lead halides (MAPbX3 or FAPbX3) are the most promising perovskite materials for a better efficiency which are easy to produce and manufacture with low cost compared with silicon solar cells.
    • Apr 5
      • Speaker: Jiazhen Liu
      • Title: How to predict popularity dynamics?
      • Abstract: An ability to predict the popularity dynamics of individual items within a complex evolving system has important implications in an array of areas. Here we propose a generative probabilistic model which distinguishes itself from existing models via its capability of modeling the arrival process of popularity and its remarkable power at predicting the popularity of individual items. Extensive experiments on a longitudinal citation dataset demonstrate that this model consistently outperforms existing popularity prediction methods.
    • Apr 12
      • Speaker: Julio Sarmiento
      • Title: Quantifying your Findings - Using MATLAB and Different Approaches to Handle Data
      • Abstract: As with any experiment, what comes after data collection is data analysis, where we derive values and make conclusions about our findings. While there exists software that are tailor made for specific kinds of data analysis (such as Igor for spectroscopy), the software may not tell you everything you may want to know. That is why learning to program custom software on available languages (like Python and MATLAB) is becoming increasingly important for physicists. From the perspective of a graduate student who had to learn most of his programming skills single handedly, we will explore how to use MATLAB to handle different sets of data and how to approach problems from different angles.
    • Apr 19
      • Speaker: Tilak Ram Thapaliya
      • Title: Quantization of Hall Resistance and Spin Hall Effect
      • Abstract: Applications of Hall sensors have been ubiquitous. It took almost a century to understand the quantum regime of the Hall effect. The Integer Quantum Hall effect (QHE) revealed the quantization of Hall resistance, which was quickly adopted as the standard of resistance measurement in metrology. Despite the great potential of the dissipationless edge states of QHE, the necessity of very high magnetic field and low temperature makes the realization of Quantum Hall devices unfeasible. The Spin Hall effect has become a promising candidate for the realization of low power consumption and high speed electronic (spintronics) devices, as it is believed to generate dissipationless spin currents. Here, I will introduce these effects and their usefulness.
    • Apr 26
      • Speaker: Sushil Subedi
      • Title: What happens when a classical particle is constrained to move over a Damaru surface?
      • Abstract: We investigate simple models to describe the scattering of non-relativistic particles from a two-dimensional Damaru surface. The exact differential cross-sections are computed and discussed. All the cross-sections are found to be independent of the incident particle energy. Scattering from a two-sheeted Damaru features both elastic scattering and absorptive scattering, the latter corresponding to particles that traverse the Damaru throat to emerge on the opposite sheet.

    Preparing for your presentation

    Giving a presentation (Beardon)

    Suggestions for giving talks (Geroch)

  • Graduate Student Seminar 2018

    The oral communications course (Graduate Student Seminar) for second-year and third-year physics graduate students meets once a week, on Fridays 11:00 a.m. - 12:00 noon, in Room 105, and is led by Prof. Rafael Nepomechie.

    The main idea is for students to gain practice in planning and presenting a talk. Each speaker is given either 20 minutes (second-year students) or 30 minutes (third-year students), with up to 15 additional minutes for questions/answers. The talks should be understandable to an advanced undergraduate student. In other words, speakers should not assume that their audience has any specialized knowledge about their topic.

    The talks are open to the entire Physics family (undergraduate and graduate students, postdocs, and faculty). Each talk is followed by a discussion based in part on the anonymous feedback provided by the audience using this evalutation form.

    Schedule and preliminary talk titles:

    • Jan 26
      • Choosing topic, title and abstract
    • Feb 2
      • Student presentations of titles and abstracts
    • Feb 9
      • How to give a good talk
    • Feb 16
      • Speaker: Rafael Nepomechie
      • Title: Exactly solvable models
      • Abstract: Exactly solvable models, such as the 2-body problem and the hydrogen atom, have served in the past as important signposts guiding our understanding of the physical world. I will briefly describe two other examples: the Heisenberg spin chain and the AdS/CFT correspondence.
    • Feb 23
      • Speaker: Jiazhen Liu
      • Title: How to predict a paper's long-term scientific impact?
      • Abstract: We consider the problem of predicting the long-term scientific impact of a paper. We describe a model for the cumulative citations, allowing us to collapse the data from different papers in a given journal into a single curve, indicating that all papers follow the same pattern. Based on our model, we can use the short-term impact of a paper to predict its long-term impact.
    • Mar 2
      • Speaker: Ana Lucia Retore
      • Title: Integrability and the S-matrix
      • Abstract: Scattering processes have played an important role in our understanding of the structures of matter. Theoretically, one studies these phenomena with the S-matrix, an object that gives the probability for the scattering to occur. However, to exactly compute the S-matrix is a big challenge even for simple systems. Current methods only work for a special case called perturbative regime. Remarkably, there are some models in (1+1) dimensions in which the S-matrix can be exactly calculated. These are the so-called integrable models. The main source of simplification can be traced to the existence of the Yang-Baxter equation. In this talk, we will describe the Yang-Baxter equation using a simple example.
    • Mar 9
      • Speaker: Tilak Ram Thapaliya
      • Title: Photolithography: A crucial step in Spintronics!
      • Abstract: Photolithography is an important process used in microfabrication such as Integrated Circuits that can be found in our smart phones, computers and sensors to transfer geometric patterns from photomask to a light sensitive chemical called photoresist on a film or substrate. It has become a topic of immense importance in microelectronics industry because it determines the smallest transistor dimensions which can be manufactured on a semiconductor chip. Here I will give some insight on the basic principles, and the methods involved in this process. Electrodes are patterned in thin films as a means of sample preparation in Spintronics research.
    • Mar 23
      • Speaker: Sushil Subedi
      • Title: Spin Multiplicity
      • Abstract: The matrix formulation of spin multiplicity is explained and used to find the number of times spin s appears in the Kronecker product of n spin j representations.
    • Mar 30
      • Speaker: Sicong Huang
      • Title: Search for exoplanets
      • Abstract: We have now confirmed the existence of over 1800 planets orbiting stars other than the Sun, known as extrasolar planets or exoplanets. The different methods for detecting such planets are sensitive to different regions of parameter space, and so, we are discovering a wide diversity of exoplanets and exoplanetary systems. Characterizing such planets is difficult, but we are starting to be able to determine something about their internal composition and are beginning to be able to probe their atmospheres, the first step towards the detection of bio-signatures and, hence, determining if a planet could be habitable or not. Here, I will review two methods that we use to detect exoplanets and how the Kepler mission carries out the methods.
    • Apr 6
      • Speaker: Jia Li
      • Title: Anisotropy of atmospheric turbulence
      • Abstract: We introduce the concept of anisotropic atmospheric turbulence, and show its effects on short- and long-distance propagation of a He-Ne Gaussian laser beam. Furthermore, we conduct the experimental study of the laser beam propagating through near-ground atmosphere on the grassy field in University of Miami (UM). The average intensity and the intensity-intensity correlation (IIC) function in the receiver plane is measured at three different channels. It shows that the IIC function displays the anisotropic information of turbulence. Our findings provide an efficient way to determine the anisotropic parameters of atmospheric turbulence.
    • Apr 13
      • Speaker: Sabit Karayev
      • Title: Flexible magnetoresistive sensors
      • Abstract: Magnetic sensors have wide application range. One of these sensors is the magnetoresistive sensor fabricated on a flexible substrate. These sensors can be applied on elastic, soft or curved surfaces, and can be used in magnetic field, motion and strain sensing, and data storage technology. Magnetic properties of these flexible magnetoresistive sensors can change when mechanical stress is produced by the substrate bending and/or stretching is applied. Therefore, for flexible magnetoresistive sensors applied in curved surfaces or used to evaluate the mechanical stress, their magnetic properties such as Magnetic Anisotropy need to be known and well controlled under various mechanical stresses.
    • Apr 20
      • Speaker: Julio Sarmiento
      • Title: The future of solar cells: The dynamics of quasi 2D Perovskites
      • Abstract: Perovskite cells are part organic, part inorganic materials that come in many different forms, but they share the trait of absorbing photons to separate electrons from holes and transport them to different parts of the cell. 3D Perovskite thin films have a high photon energy conversion efficiency and can easily transport the charges; however, they are highly susceptible to moisture thus limiting their applications. 2D Perovskite thin films are much more stable and are better at absorbing light, but they require much more energy to separate the electrons from their holes. Quasi 2D Perovskite thin films were designed to combine all the advantages of the 3D and 2D counterparts and show much promise, but not much was known about the dynamics of these films. The quasi 2D films were studied using transient absorption spectroscopy (TAS) to discover the wavelengths at which electrons in the ground state were being excited. It showed that the films grew vertically outward with increasing "n" layers of 3D Perovskite, not a single value of n and that there exist absorbance peaks that increase with n.
    • Apr 27
      • Speaker: Nathan Aden
      • Title: A guide to cryptocurrencies
      • Abstract: Given the tumultuous recent trend in bitcoin -- especially now that it has stumbled headlong into the public spotlight -- it's easy to dismiss it as just a kind of get-rich-quick dotcom bubble or as the lofty and overly rosy colored vision for the future of currency. Well, I don't know about anything as dramatic as that but, despite its reputation, it is very much an exciting and revolutionary technology that solves many of the trust problems thought to make peer-to-peer electronic cash systems impossible in a creative and widely applicable way. In this talk I will demystify the inner workings of the Blockchain technology and hopefully prepare you to start your own research on the future of Crypto.

    Preparing for your presentation

    Giving a presentation (Beardon)

    Suggestions for giving talks (Geroch)

  • Graduate Student Seminar 2017

    The oral communications course (Graduate Student Seminar) for second-year and third-year physics graduate students meets once a week, on Fridays 11:00 a.m. - 12:00 noon, in Room 105, and is led by Prof. Rafael Nepomechie.

    The main idea is for students to gain practice in planning and presenting a talk. Each speaker is given either 20 minutes (second-year students) or 30 minutes (third-year students), with up to 15 additional minutes for questions/answers. The talks should be understandable to an advanced undergraduate student. In other words, speakers should not assume that their audience has any specialized knowledge about their topic.

    The talks are open to the entire Physics family (undergraduate and graduate students, postdocs, and faculty). Each talk is followed by a discussion based in part on the anonymous feedback provided by the audience using this evalutation form.

    Schedule and preliminary talk titles:

    • Jan 27
      • Choosing topic, title and abstract
    • Feb 3
      • Student presentations of titles and abstracts
    • Feb 10
      • How to give a good talk
    • Feb 17
      • No talk - Open workshop
    • Feb 24
      • No talk - Open workshop
    • Mar 3
      • Speaker: Dharmendra Shukla
      • Title: Thermal conductivity measurement of hybrid organic-inorganic perovskites
      • Abstract: So-called hybrid organic-inorganic perovskites (HOIPs) are promising materials for photovoltaic applications, as well as for low-dimensional anti-ferromagnetism. We describe thermal conductivity measurement on a single crystal of a particular HOIP. We observe that the thermal conductivity of this material depends strongly on the crystal directions.
    • Mar 10
      • Speaker: Sabit Karayev
      • Title: How to make memory and logic devices more energy efficient?
      • Abstract: Conventional memory devices are limited by relatively high power consumption and low data storage capacity. In order to overcome these drawbacks, new devices called memory racetracks were proposed nearly two decades ago. Memory racetracks consume less power and can store more data owing to the exchange interaction in ferromagnetic materials. The latest development in racetracks offers to use skyrmions as the data carriers. Skyrmions are stable nanoscale spin configurations, which can be moved with extremely low currents. Skyrmions therefore have the potential to make data transfer and storage more energy-efficient and compact. We are trying to realize skyrmions in so-called multilayers of Pt/Co/Ir.
    • Mar 24
      • Speaker: Ibrahim Ahmed
      • Title: An Introduction to Industrial Engineering
      • Abstract: Industrial engineering is a branch of engineering that deals with the optimization of complex processes or systems. Industrial engineers analyze and design facilities, material handling systems, manufacturing and production systems, information systems and individual and group workplaces. One main field of industrial engineering is Operations Research in which mathematical modeling and optimization are used in the process of decision-making. In this talk, I will present an introduction to the interesting field of industrial engineering in general, with a focus on linear optimization problems in particular. I will also talk briefly about the work done at the Industrial Assessment Center of the University of Miami.
    • Mar 31
      • Speaker: Xi Chen
      • Title: How to improve image quality in optical systems?
      • Abstract: When light propagates in random inhomogeneous media, scintillation and beam-wander are common effects that can cause wavefront aberrations and therefore degrade the image quality in optical systems. Adaptive optics is a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions: it aims to correct the deformations of an incoming wavefront by using deformable mirrors to compensate for the distortion.
    • Apr 7
      • Speaker: Matt Haddad
      • Title: Tubes and Weyl's volume formula
      • Abstract: There exist many physical systems whose properties are localized in a tube-like region. We examine some of these; in particular, we focus on localized energy densities and explore how the total energy of such systems can be computed. In so doing, we encounter a formula discovered by Hermann Weyl that allows us to write down an expression for the volume of a tube in an arbitrary number of dimensions. We then briefly discuss some areas of active research where this technique comes into play.
    • Apr 14
      • Speaker: Durga Khadka
      • Title: Domain Wall Motion and Its Application
      • Abstract: Ferromagnetism is the result of an exchange interaction that tends to align the spins of electrons parallel to each other. For sufficiently large sample the orientation of the spins will be different in different regions so that there will be several small regions with parallel spin orientation, called domain. These individual domains are separated by boundaries called domain walls and these walls can be set to motion by applying an electric current. When a normal electric current passes through a heavy metal, a spin imbalance occurs in transverse boundary due to the scattering of opposite spin electrons: this effect is called the spin Hall effect. The spin current thus produced can create a torque on domain walls of ferromagnet and has ability to move the domain wall if we have bilayer structure of heavy metal and ferromagnet together. This property has potential application to make better memory device with less power consumption and faster access to data.
    • Apr 21
      • Speaker: Jia Li
      • Title: How to recognize objects from their scattered light
      • Abstract: During the last two decades, the polarization imaging detection of objects has become an effective method for recognizing objectÕs information, including its material type, geometric size, and roughness. Compared with the laser ranging and laser radar imaging detection methods, a variety of reports have revealed that polarization information of scattered wave plays a significant role in object detection and recognition. Nevertheless, experimental data of objects obtained using laser radars is time-consuming, expensive, and subject to atmospheric turbulence. To solve this problem, we utilized a small-sized, bidirectional reflection distribution function (BRDF) device to obtain the intensity distribution and polarization state of light scattered from objects. In our experiments, we chose the material samples by using aluminum and solar cell plates that are key components of a satellite. Results indicated that scattering polarization information provides insight into distinguishing materials of objects. It can be combined with scattering intensity information to determine the material type.
    • Apr 28
      • Speaker: Nathan Adan
      • Title: Why do physicists care about graph theory?
      • Abstract: Percolation is the process by which clusters form among groups of nodes as edges are randomly added or removed from the graph. For certain parameters governing this creation and destruction process, phase transitions occur spontaneously from a sparse graph to a single super cluster. This behavior can be used to model a wide array of phenomenon such as the connectivity of social networks or the polarization of political alignment in the blogosphere. This talk will focus on the creation and solving of a model that incentivizes nodes to form triangular shaped subgraphs with the addition of a quadratic term in the percolation equations.

    Preparing for your presentation

    Giving a presentation (Beardon)

    Suggestions for giving talks (Geroch)

  • Graduate Student Seminar 2016

    The Physics Department is starting a new oral communications course (Graduate Student Seminar) in Spring 2016. The course meets once a week, on Fridays 11:00 a.m. - 12:00 noon, in Room 105, and is led by Prof. Rafael Nepomechie.

    The main idea is for students to gain practice in planning and presenting a talk. Each speaker is given 20 minutes, with up to 15 additional minutes for questions/answers. The talks should be understandable to an advanced undergraduate student. In other words, speakers should not assume that their audience has any specialized knowledge about their topic.

    The talks are open to the entire Physics family (undergraduate and graduate students, postdocs, and faculty). Each talk is followed by a discussion based in part on the anonymous feedback provided by the audience using this evalutation form.

    Schedule and preliminary talk titles:

    • Feb 5
      • No talk - Open workshop
    • Feb 12
      • No talk - Open workshop
    • Feb 19
      • Speaker: Artem Akopyan
      • Title: The Spin Hall Effect and the Inverse Spin Hall Effect
      • Abstract: Spin Hall Effect (SHE) and Inverse Spin Hall Effect (ISHE) are physical phenomena in which charge currents generate transverse pure spin currents and vice versa. Both theoretical and experimental advancements in the field are going to be discussed, with a focus on transport experiments. In terms of applications, SHE and ISHE are essential in the field of spintronics, as they are used to generate and detect spin currents in devices.
    • Feb 26
      • Speaker: Hassan Alshal
      • Title: A Glimpse into Black Holes
      • Abstract: Black Hole is part of the spacetime fabric where gravitational effects are so strong that once it pulls anything from the surroundings, then that thing— either light or matter— can not get out of that region of the spacetime. Historical and contemporary definitions for black holes are to be overviewed together with their structures, properties and their different types. Detecting black holes directly is "mission: impossible" as they do not leak information about themselves. Nevertheless, black hole effects on the surroundings are detectable by measuring gravitational waves they produce and by many other means. Beyond the general theory of relativity, Stephen Hawking and others after him had shown it is possible to get more thermodynamical information about black holes creation and evaporation, opening doors for further development and getting better understanding to such phenomena.
    • Mar 4
      • Speaker: Ibrahim Ahmed
      • Title: Integrable Quantum Spin Chains and their Symmetries
      • Abstract: The importance of "quantum integrable" systems in physics lies in the fact that they describe many-body interacting systems where exact solutions can be obtained. In this talk I will give an overview of one of the simplest quantum integrable models, the Heisenberg spin chain. Symmetry and Lie algebra structures play an important role in the world of spin chains as a certain symmetry can lead to an explanation of degeneracy of energy eigenvalues of the model. Therefore, I will briefly discuss symmetry and try to show the relation between the Heisenberg spin chain and the su(2) symmetry. I will also discuss briefly the direction of my future work towards finding more symmetries using the so-called "quantum group" symmetry.
    • Mar 18
      • Speaker: Minzhang Zheng
      • Title: Infection Models
      • Abstract: Contagion involves the propagation of a rumor, idea, message or virus through a population, online or offline. Standard infection models such as SIR (Susceptible-Infected-Recovered) are used extensively for such outbreaks. Unfortunately modern-day outbreak profiles often lie well beyond the predictions of such models. Here we show that the common space contagion model captures outbreak profiles ranging from online pro-ISIS activity to the spread of financial rumors and mass street protests.
    • Mar 25
      • Speaker: Matt Haddad
      • Title: A Brief Overview of Kaluza-Klein Theory
      • Abstract: Over the years, many people have studied the problem of unification; that is, how to come up with a single theory that describes all of physics. This talk focuses on the combination of classical electrodynamics and general relativity via a theory first developed by Theodor Kaluza and Oskar Klein shortly after the publication of Einstein's general theory of relativity. In this theory, using a technique called dimensional reduction, our four-dimensional spacetime is viewed as part of a larger five-dimensional space, with the fifth spatial dimension being compact. Though not complete (this approach did not include the strong or weak nuclear forces), this was an important stepping stone in the development of many modern unification theories.
    • Apr 1
      • Speaker: Xi Chen
      • Title: Mie Scattering Theory
      • Abstract: In 1908 Gustav Mie published a paper on light scattering by dielectric absorbing spherical particles when he was interested in explaining the colorful effects connected with colloidal gold solutions. His paper provided an analytical solution to Maxwell's equations in terms of infinite series. During the past decade, Mie scattering theory and related computational methods have evolved rapidly and have become an indispensable tool in optical and aerosol science today.
    • Apr 8
      • Speaker: Dharmendra Shukla
      • Title: Thermoelectricity and its Applications
      • Abstract: Global warming due to extensive use of fossil fuels is becoming increasingly alarming. After using fossil fuels as our primary source of energy for decades, we have arrived at a situation where we need to look for alternatives to reduce our dependence on fossil fuels. The use of thermoelectric generators is one way to scavenge waste heat and convert it to electric power. Automobiles, home heating and industrial processes all produce enormous amounts of unused waste heat that could be converted to electricity by using high-efficiency thermoelectric materials. Thermoelectric generators are solid in nature; therefore, they are silent, reliable and scalable.
    • Apr 15
      • Speaker: Dhaka Sapkota
      • Title: Diffuse X-ray emission from the Local Galaxy
      • Abstract: The Diffuse X-ray emission from the Local Galaxy (DXL) is a series of sounding rocket missions to study the Solar Wind Charge Exchange (SWCX) and Local Hot Bubble (LHB) X-ray emission. The first launch of DXL took place in Dec 2012. The mission scanned the helium focusing cone, a high helium density region in the solar system emitting excess X-rays due to SWCX. In this talk, I will discuss the nature and locations of SWCX and LHB and some results from DXL.
    • Apr 22
      • Speaker: Durga Khadka
      • Title: Skyrmions on thin films and nano-discs
      • Abstract: Magnetic Skyrmions are nanometer-size special spin configurations found in some magnetic materials. They could be used as bits to store information. Because of their small size, less power is needed to drive them, and the flow of information would be faster. Skyrmions are therefore promising candidates for future ultra-dense information storage devices. Due to this appealing potential application, a major research effort is underway to look for room-temperature Skyrmions in inexpensive materials. In this talk, I try will explain how we can observe Skyrmionis in epitaxial films by so-called topological Hall effect and from measurements of magnetization at different temperatures. I will also discuss how nano-disk arrays could be useful to create Skyrmions.

    Preparing for your presentation

    Giving a presentation (Beardon)

    Suggestions for giving talks (Geroch)

Top