Nikhil Tilak -- Apr 18th
SSPAR is a series of talks given by students to other students. It allows graduate students to practice public speaking and giving research seminars. Our seminars are at 7pm on Thursdays in Serin 385E, so please come check us out! We have a variety of food option each week, courtesy of the GSA.
Upcoming seminars are stored here, where you can see the speaker, title, and abstract for each talk.
So much of popular culture in recent years has drawn heavily from so called “Geek Culture”. In this talk I will present a foray into one aspect of this culture, the tabletop role-playing game Dungeons & Dragons. I will discuss its beginnings, rise, and fall as well as the plights of its creators. This historical background will hopefully provide insight as to what made the game such a phenomenon and how it drew its harshest critics. I will also provide an overview of the game itself; a description of the many different versions as well as some of the hallmark features that have, in some cases, become synonymous with the game itself. Finally, I will look at the impact D&D has had on culture at large and link it back to sources more familiar to the layperson.
Previous seminars are stored here, where you can see the speaker, title, and abstract for each talk.
With the competitive nature of physics graduate school, stress is an inevitable factor. Although every student is subject to this pressure, each personal experience has the potential to differ greatly. This talk will offer several perspectives on the topic of maintaining mental health as a graduate student starting with a general presentation of the statistics and a brief look at available resources to students. We will then discuss the successes and failures of various strategies to maintain mental health taken by several students, with an emphasis on the diversity of experiences.
Seminar slides can be found here.
Since it's discovery, the Strong force interaction has demonstrated extraordinary elusiveness in being fully described and understood. To this end, the Quark Gluon Plasma (QGP) is an excellent probe to the inner workings of Quantum Chromodynamics (QCD), the field theory which describes the Strong interaction. With it's tiny shear viscosity to entropy density ratio of ~ .08, as well as being the only system for which we have seen evidence for the deconfinement of quarks, the QGP is a unique state of matter that is theoretically and phenomenologically interesting. The study of the nature of the fluid along with its transition to confined hadrons is necessarily a crossroads of many different areas of physics. I will give an overview of the field with emphasis on the hydrodynamical description of the QGP and how it is a crucial component to understanding its properties.
Human beings have strove to explain the world through various means since prehistory. Some of these early attempts showed similarity to modern physics in terms of the questions addressed. However, the method of examination has greatly evolved into what is known today as the scientific method. For this talk, we will follow history from ancient (~600 BC) to modern times and take a close look at how the study of physics has changed over time with explicit examples of the questions addressed and answers given. Many of these results will be familiar to our everyday lives as students of physics.
In this talk we will explore some current topics on studying black holes in quantum gravity. The goal will be to forgo any discussion of the AdS/CFT correspondence and to motivate the application of quantum information techniques to quantum gravity. With time permitting, we will discuss the evaporation of black holes, the information paradox, and traversable wormholes.
Dark energy (DE) is a leading candidate to explain the cosmic acceleration. Upcoming large galaxy surveys (e.g., the Large Synoptic Survey Telescope, LSST) will enable access to an unprecedented amount of data, allowing us to constrain the nature of DE (among many other things!). I will specifically talk about how we can use galaxy clustering to probe DE and how the science is entering a different regime given the statistical power of LSST. I will discuss an example systematic that we have to care about if we are to fully exhaust the statistical power of LSST, followed by a discussion of an improved estimator for measuring galaxy clustering aimed at fully utilizing the large statistical sample in the presence of systematic uncertainties.
We report on the results from our galaxy cluster search from the high signal-to-noise end of the second all-sky Planck Sunyaev-Zel’dovich (SZ) catalog (PSZ2). Through deep, optical imaging from the Kitt Peak National Observatory 4m Mayall telescope we identify the richest clusters through visual inspection and other methods. A galaxy cluster is confirmed if it is both rich (based off the number of members within 1 Mpc of the brightest cluster galaxy) and within 5 arcminutes of the PSZ2 position. From the 85 unconfirmed PSZ2 candidates we observed, we find 15 galaxy clusters (0.13 < z < 0.74), 12 of which were not previously recognized as the Planck cluster counterpart in the literature. We explore three possibilities for the low confirmation purity: that cluster counterparts are at too low or too high redshift, or are obscured by the Milky Way. We find that these options in total cannot account for the low confirmation fraction, which leads us to suggest that many of the high signal-to-noise unconfirmed PSZ2 candidates are not reliable SZ clusters.
At the foundation of solid-state physics lies band theory. Band theory helped us explain many physical properties of solids, such as electrical resistivity and optical absorption and brought theory and experiment hand to hand. In the last decade, the discovery of topological crystalline phases of matter, made us reevaluate and deepen our understanding of band theory in a profound way. We now understand that bands are topological objects and we can classify them in district topological classes. Some of these classes exhibit unique responses that are quantized and robust against perturbations making them desirable in applications. In this talk, I will present a new and exciting approach to band theory that has been fully developed in the last year and already resulted in the prediction of thousands of new topological materials. I will be focusing on conveying an intuitive understanding of the underlying concepts without overwhelming people with math.
The slow neutron capture process (s-process) is a key mechanism in heavy-element synthesis, and is responsible for approximately half of the heavy elements over 56Fe. It creates elements along the line of beta-stability via neutron capture and beta decay in low neutron flux environments such as low-mass asymptotic giant branch stars. The dominant source of neutrons for the main branch of the s-process is the 13C(α,n)16O reaction, which occurs at stellar temperatures of ∼0.1 GK (∼200 keV). This makes direct measurement of the reaction rate in the Gamow window (∼140−230 keV) experimentally challenging due to the low yields and high beam currents required. There have been international efforts to measure this reaction at astrophysically relevant energies utilizing different experimental techniques. One recent measurement, performed at Oak Ridge National Laboratory, utilized a quasi-spectroscopic approach to neutron detection with the aim of reducing uncertainties in current measurements. The experimental challenges and techniques involved with the measurement of this reaction will be discussed.
There is a dark mystery in the Milky Way -- where are the black hole remains of the first stars? To answer this question will require a brief history of "galactic archeology." We will dig through layers of ancient stellar populations to reconstruct the past, we will take core samples of the Milky Way utilizing the phenomenon of gravitational microlensing, we will measure the positions, velocities, masses, and compositions of the mystery lens objects, and we will catch the first glimpse of microlensed spectra recorded by the Southern African Large Telescope.
In our universe almost everything is out of equilibrium. With the improvement of experimental techniques we are now able to probe more and more truly nonequilibrium phenomena. Some of these are explicitly time dependent, whereas some have dissipation and external forcing. One can not explain the outcomes of these experiments by doing a perturbation over an equilibrium state. Thus it has become increasingly important to develop unconventional theoretical framework to study such out of equilibrium processes. In this talk I will give an overview of the field by examining two very different problems -- (1) Multistate Landau-Zener Problem, and (2) Two Atomic Clocks Coupled to a Bad Cavity.
The Star Formation History (SFH) is a record of when a galaxy formed its stars. Physical processes that regulate galaxy growth - inflows and outflows of gas, mergers, supernova explosions and more - leave imprints in the SFH. Studying the SFHs of galaxies across a range of epochs thus gives us insights into galaxy evolution, and the mechanisms responsible for it. Well motivated analysis techniques allow us to infer the characteristics of SFHs using multiwavelength observations from large galaxy surveys. This allows us to better estimate quantities like the masses of galaxies and the rates at which they are forming stars. Tracing back galaxies in time along their SFHs allows us to estimate these quantities not only at the epoch of observation but also at previous epochs. Additionally, looking at SFHs across different simulations allows us better understand how different physical processes affect galaxy growth and set the diversity in galaxies we see in the universe today. Finally using observations in conjunction with simulations allows us to set useful constraints on the relative strengths of the processes that shape galaxies.
In this presentation, I will present various Monte-Carlo techniques used to simulate the phase transitions. As a first example, we will see how one can see all the features of a second-order phase transition through the Ising model. I will then explore other important Monte Carlo techniques such as global updates, overrelaxation steps, and parallel tempering. Although using these techniques on the Ising model is like opening a peanut with a sledgehammer, we will see that in the case of certain models, such as the hexatic-nematic XY model, these techniques are crucial to accurately describe the phase diagram.
What can be determined about a complex landscape or network by moving through it in the most unintelligent way? This talk will answer this question by presenting a formalism which combines Bayes' theorem with random walk theory. We will then delve into applications in the worlds of computer science and life with an emphasis on epidemiology.
This SSPAR was in the structure of an advisory panel, rather than the traditional presentation. Several of the senior students discussed both their personal experience and gave general advice on the dos and don'ts of physics graduate school. This was an open discussion, not a lecture.
Come join me for an hour-long storytelling section which I tell you everything you need to know about the Jame’s Webb Space Telescope — the long-anticipated successor to Hubble! What do we expect to see and to learn with it? And of course I will also prepare you with a crash course on modern cosmology and wrap up with what semi-analytic modelists are doing to prepare for the upcoming excitement.
In this talk we'll discuss the theory, application, and uses of Dynamical mean field theory (DMFT). We'll begin with a brief introductory example of mean field theory for the classical Ising model. From there we'll look towards discussing mean field theory for a specific quantum system, the Hubbard model. Approximating this model will lead towards a mapping of our many body problem to a simpler impurity problem. From here the DMFT assumption of local lattice interactions will be asserted. Subsequent to the theory, we'll look at the application and successes of DMFT in describing strongly correlated systems.
Confinement is one of the largest outstanding problems in quantum physics. This describes the curious phenomenon that quarks do not appear in nature by themselves. This talk will review some of the basics and give a broad overview of some modern developments in the subject.
So much of popular culture in recent years has drawn heavily from so called “Geek Culture”. In this talk I will present a foray into one aspect of this culture, the tabletop role-playing game Dungeons & Dragons. I will discuss its beginnings, rise, and fall as well as the plights of its creators. This historical background will hopefully provide insight as to what made the game such a phenomenon and how it drew it harshest critics. I will also provide an overview of the game itself; a description of the many different versions as well as some of the hallmark features that have, in some cases, become synonymous with the game itself. Finally, I will look at the impact D&D has had on culture at large and link it back to sources more familiar to the layperson
Angular-resolved photoemission spectroscopy (ARPES) is an experimental tool in the study of quantum materials that has steadily risen since the 1980s to become one of the key methods to probe materials. In this talk, I will review the basic concepts of electron spectroscopy and its link to the spectral function. We will then look at the experimental challenges, what a set of ARPES data can tell us about the material, and recent progress made by ARPES studies. Its role in the study of unconventional superconductivity will be reviewed.
Electron beams are used in a wide variety of physics applications from studying material properties with Electron Microscopes to studying Parton Distribution Functions at electron accelerators around the world. The history and development of electron beams will be discussed starting with the discovery of the electron and continuing on to the proposed Electron-Ion Collider. I will also delve into electron beams in astrophysics and how these beams can provide important constraints for Chiral Effective Field Theory. Some time will also be devoted to electron beams in commercial applications, including electric arc furnaces, solar cell production, and 3D printed rocket engines capable of reaching orbit.
We will present a slew of abstract definitions, ranging from fiber bundles to connections. After building a working dictionary of terms through simple examples, we will reveal that these mathematical objects are actually quite familiar to the working physicist, playing integral roles in general relativity, gauge theory, and condensed matter. By the talk's end, members of the audience will find themselves sewn into the modern language and warm for winter.
The basic physics and chemistry of the distillation process will be presented, followed by a discussion of the various categories of distilled spirits and their attributes.
As technology develops, many traditional arts also changed. When it comes to painting, the emergence of digital painting have greatly increased the efficiency for people doing illustration, 3G design as well as animation. For most painting lovers, digital painting makes it cheaper and easier to express themselves through painting. Here I’ll give an overview about what I know about both professional digital painting and some typical drawing styles, and give some good examples of successful works.
There is building evidence which suggests that many galaxies are highly influenced by the presence of an active galactic nucleus (AGN) at their center. This highly luminous and compact region is thought to heat and drive out gas from the surrounding galaxy via a number of feedback mechanisms, which ultimately allow the AGN to couple to the host galaxy and co-evolve. I look at the motivations behind studying AGN feedback, evidence of feedback occurring in the near and distant universe, and how it will be studied in the future.
The search for a robust platform capable of quantum simulation and computation has led to a growing interest in superfluids with p + ip pairing symmetry. These superfluids are expected to possess zero-energy Majorana bound states which could exhibit the non-abelian statistics necessary for a topological quantum computer. In this talk, we investigate the non-equilibrium dynamics of the two dimensional BCS Hamiltonian with p-wave symmetry. We perform numerical simulation of a system which has undergone a quantum quench of the BCS order parameter. It is known how a system which begins in a p + ip state of the p-wave Hamiltonian evolves, but we would like to investigate the stability of trajectories whose initial conditions deviate slightly from those of the p + ip state. These dynamics can potentially be realized in ultracold gases and could provide experimental verification to the predicted behavior.
Models of nuclei far from stability rely heavily on their single particle structure, which constrains the location and nature of nuclear states. The Shell model predicts magic numbers of protons and neutrons which form shell closures in stable isotopes, analogous to noble gases in atomic physics. As studies move towards unstable nuclei, more experimental data is needed to provide these constraints. With the use of RIBs (Radioactive Ion Beams) in inverse kinematics, experiments can populate states in unstable nuclei and probe their characteristics through (d,p) reactions. This presentation will include the methods used to extract excitation energies, spins, parities and spectroscopic factors of populated states in neutron rich nuclei around the N=82 region. The 132Sn(d,p)133Sn reaction will be discussed, showing the single particle states above the N=82 neutron gap, as well as preliminary results for 134Xe(d,pg)135Xe which utilizes both charged particle and gamma ray detection in coincidence.
The topological classification of matter, introduced a paradigm shift in understanding quantum phases of matter. An example of a topological classification is based on the Chern-Simons axion coupling, a topological invariant determined from the ground state of a crystal. After providing an overview of the basic concepts behind the topological classification of matter, i will introduce axion insulators. Finally i will describe my preliminary results working with Prof. Vanderbilt to study a minimal tight-binding model for the pyrochlore structure.
With the advent of high performance computing, machine learning has been widely adopted by several communities to help with increasing efficiency/speed and in some cases even to aide in solving long standing problems. Physics is no exception with machine learning algorithms helping in several areas of current research for example in astronomy, cosmology and high energy physics to name a few. We begin the talk with a general introduction to neural networks architecture and highlight a few of the models that are in vogue. As physicists, often we deal with issues where given a dataset, one has to either classify it amongst a basis of known phenomenon or extract information by employing regression techniques. We proceed to talk about both these general type of problems and provide examples of ML models that at times end up learning distinctions without being explicitly told, which might be scary. Finally, we will show a selection of problems and quiz the audience on the type of ML model or just simple statistics one would use to solve them.
In January the union will begin renegotiating the university’s graduate student contract. These negotiations include raises, decreased insurance costs, and hopefully more plentiful and stable TA/GA lines for our department. For this SSPAR we will discuss details of the contract negotiations and the funding situation for our department.
An overview of the empirical prevalence of mental illness among graduate students in science is presented, with a particular focus on depression and suicidal ideation. Methods for addressing mental hygiene are discussed, in addition to resources for those seeking care at Rutgers and generally.
In this talk, I will present the Berezinskii-Kosterlitz-Thouless phase transition, a first insight into a phase transition in which there is no long-range ordering, but rather one in which topological objects, vortices, influence the dynamics. After introducing the subject, I will show how this applies to the theory of melting of 2D crystals, with finally a word about my own research on a generalized BKT model.
After an informal introduction to some aspects of field theory and dark matter model building, I will talk about how we can start from relativistic quantum field theory and obtain a non-relativistic description of forces, potentials, and their bound states. I will then go over some non-relativistic effects, namely Sommerfeld enhancement and capture to bound states, that can affect the behavior of dark matter candidates today. Finally, I will focus on a particular dark matter model, which is historically motivated by supersymmetry, and specifically study its bound state spectrum.
I will present an overview of Chiral Perturbation Theory (ChiPT) and how it can be useful for experimentalists and calculating physical observables. There will also be discussion of the MUSE experiment and how the pion-nucleon scattering background in that experiment can be used to expand the existing low-energy data set. The relationship between ChiPT and pion scattering will be discussed at length.
Not all graduate students are destined to continue along the academic path. Many of us choose to leave the field of physics in pursuit of jobs in industry, journalism, advocacy, and teaching. Each week, our department imports several guest speakers who have been successful in academia, but other stories are much more rare. Over the past year, I've documented my background research into leaving academia as well as my personal journey to obtaining a job in data science. In this talk, I'll share it all with you, and I'll try to do it in a way which doesn't make me sound like a shill for a data science incubator.
Fountain pens or FP are used in all sorts of industrial applications and have been a cornerstone of theory work. We show the historical and practical functions of the FP. We also explore the state space available for FP's in this talk along with the connections between these states along with the connection of certain liquid states.
The universality of certain physical phenomenon will be explored. First, we will get a quick look at various systems that seem unrelated: the classical XY model for ferromagnetic spins, superfluids, liquid crystals near their melting transition and the 2D Coulomb gas. Though a brief introduction to the Renormalization Group, we will see that those systems present the same universal phase transition: the Kosterlitz-Thouless phase transition.
From large gap insulators to systems with metal-insulator transitions, transition metals (TM) and their compounds possess many specific and unusual features. They display a lot of interesting phenomena such as colossal magnetoresistance, magnetoelectricity and high Tc superconductivity. TM compounds are also the basis of the physics of systems with strong correlations -an area of extensive modern day research. In this talk, I will try to shed some light on some interesting details about TM compounds from Dynamical Mean Field Theory (DMFT) perspective.
We present a brief overview of the pipeline of hardware and software involved in modern music production.
Within the genome of an organism, synonymous codons (triplets of nucleotides which result in the same amino acid) are found in unequal proportions. There are various potential causes for this codon bias. Several major sources are adapted into a mean-field, stochastic, evolutionary model, and their relative importances are compared. This proposed model also results in various other universal features of genomes such as the distribution of protein lengths.
The 1998 Fields Medal was awarded to Richard Borcherds for his proof of what is known as the Moonshine conjecture. With this proof came the introduction of structures known as vertex operator algebras which have been extremely fruitful in string theory. This has also opened the doorway to a large series of mysterious and deep connections between number theory, finite group theory, and conformal field theory. In this talk we will take a brisk walk through many of the exciting features of Moonshine, particularly Monstruous Moonshine, keeping a close eye to the physical motivation.
Generating Strain in any crystal causes its electro-optic properties to change. 2D crystalline materials like Graphene, hexagonal Boron Nitride and MoS2 can survive significantly higher strains than 3D materials owing to their high mechanical strength. This enables us to engineer the electro-optic properties of these 2D materials simply by generating strain in them. Moreover, many of these 2D materials have been predicted to show a very strong Piezoelectric effect. This is particularly exciting because of the potential applications in self-powered electronic devices and sensors.
Cosmological simulations seek to recreate the process of galaxy formation and evolution as accurately as possible. As resolutions get higher, it becomes necessary to implement a more realistic prescription for star formation. With this motivation, I discuss the initial mass function, which describes the mass distribution of stars at the time of formation. I will consider proper sampling methods for this function, and prospects for implementing them into cosmological simulations. Pretty pictures of space guaranteed.
In this talk we will be having fun with 1 dimensional quantum systems, including the famous Heisenberg XXZ spin chain. We will see how the scaling limit of the spin chain results in the Thirring Model, a Quantum Field Theory of Dirac fermions . Along the way, we’ll touch on a number of key physics ideas such as Universality and Lorentz Invariance.
The Ricci flow is a natural generalization of the heat equation to the geometry of manifolds. It is fundamentally related to the renormalizability of certain field theories called nonlinear sigma models. In the 1980's, the Ricci flow was studied in differential geometry as a tool to investigate the decomposition of three dimensional manifolds. These studies ultimately led to the proof of the Poincare conjecture. In this talk, we will look at solutions to the Ricci flow in two and three dimensions and what this means for physics.
Mental health problems among the population of graduate students in science will be discussed, with a particular focus on depression and suicidal ideation. The speaker will present on the empirical prevalence of such issues, in combination with an overview of resources available local to Rutgers, practices of hygiene, and coping skills.
Ever since RHIC announced the creation of the quark gluon plasma in relativistic heavy ion collisions, study of the strongly interacting, high temperature and high energy density has elucidated several key features of QCD. We at Rutgers are experts in creating a tomographical picture of the QGP by utilizing fully reconstructed objects called jets, that travel through the medium on its way to our detectors. In this talk, I will attempt to draw a state of the art qualitative (and quantitative to a degree) picture of what happens to a parton moving through this dense (colored) medium and our takeaways from measurements at the LHC.
We study the exact dynamics of 1D interacting Bose gas in the presence of a spatially uniform, time dependent Electric field. We begin by introducing and exactly solving the Lieb-Liniger model of 1D Bose gas, in the absence of any electric field and proceed to solve the time dependent Schrodinger's equation in the presence of a time dependent linear potential.
I'll be going over the physics of the SeaQuest experiment, the Drell-Yan process, and how we use it to probe the quark distributions of the nucleus. There will also be discussion of general issues in nuclear structure including the EMC effect, the Gottfried Sum Rule, and quark flavor asymmetry.
Despite what Edwin Starr might tell you, string theory is a very useful tool for physicists that has led (and probably will lead) to many new ways of thinking about quantum physics. For example the study of string theory has lead to the discovery of exotic quantum theories without a known Lagrangian description and has lead to the discovery of the AdS/CFT correspondence. In addition, string theory gives us a way to study strongly coupled quantum field theories, which may potentially lead insight into fundamental problems such as quark confinement.
In 2010 Randolf Pohl measured the radius of the proton to be 4% smaller than the accepted CODATA radius with an unprecedented accuracy. This may not sound significant but the Proton Radius Puzzle is a high profile issue within the nuclear physics community. In this talk the Puzzle will be discussed and the Muon Proton Scattering Experiment’s place in attempting to resolve the Puzzle will be presented.
Markov chain Monte Carlo is arguably one of the most important algorithms and is extensively used in modern simulations and numerical methods. A brief overview of Markov chains and Monte Carlo will be introduced. More importantly, for modern graduate students not only could Markov chain Monte Carlo be useful, but the advent of pizza is also very important in physics.
Beams have always been used by physicists to study many different aspects of nature. From your simple table top diffraction experiment to the largest operating experiment on the planet, we all use some form of either a beam to probe or scatter or annihilate objects. In this talk, I will focus more on the particle beams at CERN and particularly how they produce and maintain said stable beams for physics collisions. This procedure of generating a beam of highly focused particles from a canister of gas contains many different steps, some of which are a phenomenal feat of scientific ingenuity and engineering receiving the highest award for scientific research, the Nobel Prize in 1984. This has also led to remarkable public utility in many fields such as medicine and consumer electronics (on which you are all reading this abstract).
A multistate Landau-Zener (MLZ) Hamiltonian is used to model numerous non-equilibrium experiments involving cold atoms, quantum dots and quantum dot molecules. We recently showed that all the known MLZ problems either reduce to the 2 X 2 Landau Zener problem or belong to a family of mutually commuting Hamiltonians (that are polynomial in time). Based on this classication we identify previously unknown MLZ problems, explicitly obtain their solutions and discuss relevant experimental scenarios.
One of the questions of fundamental physics is understanding the asymmetry between electric and magnetic fields: namely why is there electrically charged matter but no magnetically charged matter. The question of why there are no monopoles have baffled physicists for a very long time. The idea of these "particles" has been revisited at every theoretical revolution in the past century by people such as Dirac, 't Hooft, Polyakov, and many others. In this talk we will talk about the role of monopoles in modern physics and how they relate to cosmology, condensed matter, particle physics, and the role of confinement.
Interacting systems in quantum physics are common place, but only few systems are integrable. In this talk we discuss mostly Lieb-Liniger system, which is integrable exactly using Bethe Anstaz. We will also then talk about quantum quenching a free bosonic system with Leib-Liniger Hamiltonian using the Yudson representation.
During its 13.8 billion-year-long evolution, our Universe has undergone many phases and phase transitions. Two of the most interesting events in cosmic history are the formation of the first galaxies and cosmic reionization. Galaxies are regarded as the fundamental entities of large-scale structures in the Universe, which their formation strongly dependent on the cosmic environment. On the other hand, these galaxies can also provide feedback effects that can alter the cosmic environment, hence indirectly shape future formation activities. Galaxy formation is inseparable from the evolution of the cosmic environment. Therefore, understanding the interplay of the two can help us better understand the overall cosmic evolution history.
Given its scalability and compatibility to current silicon industry, superconducting qubit has become an ideal candidate for realizing quantum circuits. In order to understand and achieve reliable quantum operation, I would like to focus on the fundamental building blocks of superconducting circuits, which is the Josephson junction. In this talk, I will introduce the properties of Josephson junctions elements, the experimental approaches to fabricate and characterize Josephson junctions, and investigate the possible application of superconducting qubits.
Since their invention in the 17th century microscopes were thought to have enjoyed unlimited improvement, but 1873 Ernst Abbe developed the diffraction limit. Superresolution microscopy are techniques that work around the diffraction limit to improve resolution more than 10 fold with visible light and, in some cases, promise unlimited resolution. Unlike their high resolution, diffraction limited cousins such as X-Ray microscopy, these methods allow for greater range of samples and are paving the way for readily accessible widefield, live imaging.
Galaxy clusters are the largest gravitationally bound structures in the Universe. Consisting of thousands of galaxies, hot intra-cluster gas, and dark matter, they are also the most massive structures known. Since they are so dense, they cause light from background sources to be bent around them, a phenomenon known as gravitational lensing. The bending both distorts and magnifies these distant sources, allowing them to be more easily detected and studied, which has earned cluster lenses the name 'cosmic telescopes'. In this talk I will give background information on gravitational lensing and discuss techniques in how we model these complex mass distributions.
Black holes are mysterious objects which came out of general relativity (GR). They taught us a lot about GR in the past and now they are playing a key role in understanding quantum gravity. They are also being used as tools in understanding highly coupled gauge theories, certain condensed matter systems and the list goes on. But what is inside a black hole is still a mystery. I will give a qualitative explanation of how a black hole curves space-time and then I will briefly go over hawking radiation and the puzzles which come out of it. I will then give a summary of some important papers which try to solve these puzzles thereby revealing a plausible structure of the black hole. In the end I will talk about the current research relating AdS/CFTto black hole interior.
I present an overview of a study of the phase and interface properties of pure Sn by molecular dynamics, and describe the application of non-Boltzmann simulation to this end. Several orientations of both alpha- and beta-Sn crystals have been simulated in direct coexistence with liquid at constant pressure, with potentials provided by the Modified Embedded Atom Method (MEAM). Simulations are carried out for pressures ranging from zero to 10 GPa and temperatures from 200 K to 1000 K. A complete phase diagram for Sn is mapped on this interval, and comparison is made between competing sets of MEAM parameters with regard to phase stability.
Entanglement Entropy in the recent year has been a powerful tool to provide with new insights in various areas of Physics. One class of such attempts was to provide us insights about gravity in the context of gravity. Inspired by the approach taken by Ted Jacobson in deriving the Einstein's equations starting from Thermodynamical arguments. We are exploring such a possibility starting from the Quantum informatic arguments. We take condition of positivity of relative entropy arising from Unitarity quantum mechanics and imposing these arguments in the context of holography with the help of Ryu-Takayanagi formulation. Imposing these relative entropy conditions on the Quantum Field theories with Holographic dual, we explore constrains imposed on the gravitational theories allowed in the holographic bulk.
Heavy Ion physics has a rich history of studies carried out at Berkeley, SPS, RHIC and now at CERN where nuclear physicists are pushing the boundaries of our understanding of the strong force. At such high energies, heavy ion collisions create a viscus, high temperature and strong force mediated fluid called the quark gluon plasma (QGP). Here are Rutgers, we are involved with the CMS detector and study the transport and topological properties of the QGP. I’ll give a brief introduction to the field, our motivation and what we have learnt so far from the first run followed by an outlook to the future in this experiment driven field.
The Standard Model of Particle Physics is an enormously successful theory. It is also an enormously rich and complicated theory. Much of that richness and complexity stems from quantum chromodynamics (QCD), the gauge theory of the strong interaction. QCD describes how quarks interact via gluons to form protons, neutrons and, indeed, most of the visible matter in the Universe. Unfortunately QCD cannot be solved analytically (at least, not yet), because it is inherently nonperturbative and confining. In other words, we can never observe individual quarks, only their bound states, such as protons and neutrons. The only method we have for a rigorous understanding of QCD is lattice QCD, in which we discretise spacetime and study the properties of QCD statistically, usually on supercomputers. I will introduce lattice QCD, discuss some of its successes and challenges and, of course, how to build a proton.
The Standard Model describes the matter content and interactions of the most fundamental particles of nature. It is one of the most successful theories in the history of physics in both prediction and experimental verification. However, there are many problems with the Standard Model, such as lack of gravity, description of dark matter, and matter/anti-matter asymmetry. In this talk we will describe some of these issues and some of their proposed resolutions.
In the mid-twentieth century, physicists made the surprising discovery that square arrays of completely random numbers can be useful for characterizing Hamiltonians of real quantum systems. A cornerstone of random matrix theory is the nearest neighbor level spacing distribution: i.e. the histogram of spacings between consecutive eigenvalues. For typical random matrix ensembles and generic quantum systems, eigenvalues exhibit repulsive correlations. For special classes of physical models, however, the eigenvalues lose this repulsion and do not see each other at all. These systems are called integrable and my research has investigated the level statistics of ensembles of integrable matrices. Come see the results!
Super-resolution techniques are a means for us to go beyond the Abbe diffraction limit without the need for potentially harmful elections or high energy photons. These techniques, along with clever experimental methods, have allowed us to better analyze biological specimen without killing them or freezing them, and to overcome issues common and advance microscopy techniques bring to live biological studies. This talk will motivate the need for super-resolution, give an overview of the two types, 'true' and 'functional,' and briefly discuss how compressed sensing - a sparse signal analysis method - and super-resolution work together to allow for analysis of more complex systems.
Instantons are non-perturbative solutions to the classical equations of motion which have non-trivial topology and are relevant to quantum phenomena. In standard quantum mechanics, they primarily determine tunneling and decay rates. However in quantum field theory, they also contribute to a class of operators which break chiral symmetry and can lead to baryon decay. This talk will give an introduction to these non-perturbative solutions and how they lead to these unexpected quantum effects.
Dynamical Mean Field Theory (DMFT) is a powerful method to deal with strongly correlated materials where quasi-particle approach used in band structure calculation completely fails. In order to perform a realistic calculation, DMFT is combined with local density approximation (LDA+DMFT) and it is widely used in solids to predict properties of correlated systems. Here one of the simplest strongly correlated systems, the hydrogen molecule H2, is used as a testbed to develop a parameter-free LDA+DMFT framework.
Galaxy clusters are the most massive virialized structures in the universe. The evolution of cluster galaxies is highly dependent on the physics of their environment. I will give examples of how neutral hydrogen is dissipated in clusters and how such mechanisms can quench star formation.
A major goal of materials science is the discovery and design of new functional materials. Historically this process consisted of synthesis and experimental characterization of candidate materials, many of which would then be found to be neither interesting nor useful. First principles techniques allow for the structure and properties of candidate materials to be predicted before synthesis, providing valuable input for experimentalists. In this work first principles methods are used to explore candidate ferroelectrics in the LiGaGe structure type.
Relativistic heavy ion collisions were first conceptualized by Fermi and Landau independently as a study of the bulk properties of nuclear matter. This was a tool to explore multi-particle productions/interactions, hadron gas systems, thermalized equilibrium and many such novel concepts. From the early 1-2GeV(Giga electron volt) per nucleon at Berkeley and Dubna to the current 200 GeV/nucleon at RHIC, Brookhaven National Lab and 2.76 TeV (tera electron volt)/nucleon at the LHC, we have uncovered many interesting phenomenon. The formation of strongly coupled medium (often called as the quark gluon plasma) is one of the main discoveries and I will focus my talk on the studying its properties. We will start with a conceptualized study of the theory/intuition behind the formation of such a medium and study some of its properties with experimental probes.
The LHC (Large Hadron Collider) revealed the existence of a Higgs-like particle providing the missing piece of the Standard Model. With the forthcoming restart of the collider at an ever-higher center of mass energy, techniques are being developed to face the new run challenges and to provide insight to what lies beyond the current understanding. Existing tools and ideas for a Stealth Supersymmetry search at the CMS (Compact Muon Solenoid) Experiment, will be presented at this talk, regarding boosted topologies involving photons and jets in the final state.
The Standard Model is one of the greatest achievements in physics of the past 50 years, being touted by many as the most successful theory of nature. It precisely describes many observed phenomena, including both electromagnetism and the interactions of nuclear particles; but it is not complete. One of the largest flaws of the standard model is derived from a collection of cosmological observations which points to the existence of a new type of matter which is not described standard model. While many dark matter candidates have been proposed with varying degrees of success, there is still no single theory of dark matter which has been universally accepted. In this talk, a new dark matter candidate will be proposed originating from the Higgs sector of grand unified theories after symmetry breaking at the grand unification scale.
The DMFT (dynamic mean field theory) method, first introduced to study the metal insulator transition (MIT) behind the Hubbard model in infinite spatial dimensions, has been merged with the traditional density function theory (DFT), which is capable of capturing the correlation effect missed by DFT. In this talk, the DMFT method is discussed at some details, followed with a discussion on MIT. Next we introduce a formalism based on effective action to combine DFT and DMFT and use it to study the alpha-gamma transition in elementary cerium.
Quark-gluon plasma (QGP) can be produced reliably for study in the laboratory using ultra-relativistic heavy ion collisions. These collisions are achieved by using the Large Hadron Collider (LHC), and then recorded at the Compact Muon Solenoid (CMS) Experiment. Events known as jets are readily observed and used as probes to deduce properties of the QGP medium. Jet shapes and momenta are expected to be altered by the medium, as well as their production cross sections. Using specific tagging algorithms, one can identify the flavor of the parton which started the jet. Thus modifications due to the presence of a hot and dense medium can be parameterized as a function of jet-flavor. In this talk, results at CMS involving heavy flavored jets are summarized and discussed.
Conformal field theories are related to models of statistical physics at critical point. These theories are epsecially interesting in two dimensions because the group of local conformal transformations is just given by holomorphic functions. Wess-Zumino-Witten models are a class of CFTs whose solutions are characterised by affine Kac-Moody algebras. There is a close connection between Chern-Simons theory on a 3-manifold with a boundary, and a Wess-Zumino-Witten conformal field theory on that boundary. This connection is made explicit by identifying a basis of the Hilbert space of the CS theory with the set of characters of the corresponding WZW theory. I attempt to make this correspondence more explicit, and provide illustrative examples.
We can experimentally probe nuclear structure with single nucleon transfer reactions, such as (d,p), and characterize its shape with parameters like the spectroscopic factor and asymptotic normalization coefficients (ANC). Determining spectroscopic information for neutron rich nuclei near the N=50 shell closure is important in both astrophysics and nuclear physics for understanding r-process solar abundances and nuclear structure far from stability. Mukhamedzhanov and Nunes have proposed a new method of measuring a single particle transfer reaction at both low (peripheral reaction) and higher (less-peripheral) energies that should enable spectroscopic factors to be more reliably deduced, with uncertainties dominated by the experimental cross-section measurement rather than the shape of the single-particle nucleon-target interaction.
Using gases of ultra cold atoms and counter propagating lasers it is possible to directly realise many theoretical models developed in the context of solid state physics. The amount of control and precision afforded by these experiments puts new emphasis on theoretical descriptions that can be solved exactly. In this talk I will describe these experiments, what an exactly solvable model is and one way to exactly solve an exactly solvable model.
Transport on networks is an important function for various biological systems. Having a full theory of transport would be highly valuable, but this task has proven to be a challenge. One method that was introduced by Gallos et al to help develop these ideas further was the concept that renormalization can be applied to bionetworks.
Astronomers love showing plots of any kind. One, called the spectral energy distribution (SED), is particularly useful for characterizing the radiative processes in astrophysical systems. I will present the SED of a prototypical star forming galaxy and explain the wide range of physics that give rise to its features.
This website was designed by John Wu, the previous webmaster of the Physics and Astronomy GSO, and is maintained by current Vice President Willow B. Kion-Crosby who hosts and organizes the SSPARs. The SSPARs are funded by the GSA.
If you'd like to give a talk, please send a message to Willow.