Gravity Group Seminar, Will Coulton (Princeton University) "Cosmology and astrophysics from the bispectrum"
Mar 31, 2017 · 12:00 p.m.– 1:00 p.m. · Joseph Henry Room
Cosmology and astrophysics from the bispectrum
The three point function of the cosmic microwave background (CMB) is an ideal place to study CMB secondary sources as there is no noise bias and CMB secondaries are the dominant contribution. In this talk I will discuss my work measuring the bispectrum from radio galaxies, dusty star forming galaxies and thermal Sunyaev Zel'dovich sources in ACT and Planck maps. I will then discuss what we hope to learn from the bispectrum with ongoing surveys.
Mar 31, 2017 · 1:45 p.m.– 2:45 p.m. · Jadwin A06
In this talk, I will give an answer to the question “which QFT states holographically describe the emergence of semiclassical (conformal) geometry?” via a new construct in QFT: the causal density matrix. This new construct relies on the “lightcone cut” approach to spacetime emergence, and generalizes it to arbitrary QFTs (that may or may not have holographic duals). In the presence of a semiclassical spacetime, lightcone cuts explain both the emergence of holographic dimensions and the way in which geometry is encoded in a holographic dual. Properties of the causal density matrix indicate that some features of quantum error correction are more general than AdS/CFT. Within AdS/CFT, I will argue that the “reduced” causal density matrix is dual to the causal wedge.
Biophysics Seminar - Raghu Parthasarathy, U Oregon "Glimpses of Gut Microbes in their Physical World"
Apr 3, 2017 · 12:00 p.m.– 1:00 p.m. · Joseph Henry Room
In each of our digestive tracts, trillions of microbes representing hundreds of different species colonize local environments, reproduce, and compete with one another. Little is known about the physical structure and temporal dynamics of gut microbial communities: how they grow, fluctuate, and respond to perturbations. To address this and investigate microbial colonization of the vertebrate gut, my lab applies light sheet fluorescence microscopy to a model system that combines a realistic in vivo environment with a high degree of experimental control: larval zebrafish with defined subsets of commensal bacterial species. Light sheet microscopy enables three-dimensional imaging with high resolution over the entire intestine, providing visualizations that would be difficult or impossible to achieve with other techniques. I will describe this approach and focus especially on experiments in which a colonizing bacterial species is challenged by the invasion of a second species, which leads to the decline of the first group. We find that responses of bacteria to the mechanical contractions of the gut, and to contact-mediated inter-bacterial killing, can dictate apparent competition between microbes, suggesting a major role for physical mechanisms in guiding the composition of the gut microbiota.
Apr 3, 2017 · 2:30 p.m.– 3:30 p.m. · Bloomberg Lecture Hall - Institute for Advanced Study
Precision Frontier Seminar | Matthew Low, School of Natural Sciences, IAS | “Prospects for direct detection of the Cosmic Neutrino Background"
Apr 4, 2017 · 1:30 p.m.– 2:30 p.m. · Bloomberg Hall of Physics Library - Institute for Advanced Study
Pheno & Vino Seminar, Yotam Soreq, MIT, "Probing new light force mediators: from atomic physics to LHCb"
Apr 4, 2017 · 4:00 p.m.– 5:30 p.m. · Jadwin 303
In this seminar we explore the potential of probing new force carriers, which may be the portal to dark sectors, in the LHCb experiment and by precision isotope shift spectroscopy. We propose an inclusive search for dark photons at the LHCb experiment. For Run 3 of the LHC, we estimate that LHCb will have sensitivity to large regions of the unexplored dark-photon parameter space, especially in the 210–520 MeV and 10–40 GeV mass ranges.
In addition, we explore the potential of probing new light force-carriers, with spin-independent couplings to the electron and the neutron, using precision isotope shift spectroscopy. We show that the result of these measurement can be interpreted as bounds on new physics with minimal theory inputs. We apply the method to existing Ca+ data and project its sensitivity to possibly existing new bosons using narrow transitions in other atoms and ions. Provided no deviation from the standard model, future measurements could improve the current Ca+ bound by five orders of magnitude and even reach unprecedented sensitivity for bosons within the 10 keV to 10 MeV mass range.
Hamilton Colloquium Series - Tomasz Skwarnicki, Syracuse University; "Heavy flavor spectroscopy at LHCb"
Apr 6, 2017 · 4:00 p.m.– 5:00 p.m. · Jadwin A10
Hadrons with heavy quarks play a special role in studies of structures created by strong interactions. The LHCb experiment, with the large production cross-sections, its hadron identification capabilities and triggers optimized to collect events with bottom and charm quarks, has reached a new level of sensitivity in detecting new, interesting states in baryon and meson sectors. Some of these states have been expected, like newly discovered five excitations of the doubly-strange and charmed baryon. Some of them are spectroscopic puzzles, like potential pentaquark states or, reported recently, four tetraquark candidates with hidden charm and strangeness. I will discuss the LHCb results on heavy hadrons and put them in a broader context of hadronic spectroscopy.
Apr 10, 2017 · 12:00 p.m.– 1:00 p.m. · Joseph Henry Room
Apr 10, 2017 · 1:15 p.m.– 2:30 p.m. · PCTS Seminar Room
In electronic systems, chirality is an interesting and useful property that expresses the system's ability to discriminate between forward and backward propagation along certain directions. Edge states in the quantum Hall effect provide a classic example. Recently, materials exhibiting chirality in the absence of an applied magnetic field have come into the spotlight. Here, the Berry curvature inherent in the material's band structure crucially alters the motion of free carriers, leading to a variety of interesting phenomena such as the intrinsic anomalous, spin, and valley Hall effects. In this work we show that the interplay between electron-electron interactions and Bloch band Berry curvature leads to new types of electronic collective excitations at system boundaries, with a variety of properties of both fundamental and potential technological interest. I will discuss the resulting "chiral Berry plasmons" that propagate along the edges of 2D systems and, time permitting, the "Fermi arc plasmons" that arise from the peculiar kinematics of electrons near the surfaces of Weyl semimetals. Experimental signatures and candidate materials will be discussed.
Apr 10, 2017 · 2:30 p.m.– 3:30 p.m. · PCTS Seminar Room
Hamilton Colloquium Series - Philip Kim, Harvard University; "Unusual quasiparticle correlation in graphene"
Apr 13, 2017 · 4:00 p.m.– 5:00 p.m. · Jadwin A10
Interactions between particles in quantum many-body systems can lead to a collective behavior. In a condensed matter system consisting of weakly interacting particles, a propagating particle interacting with its surroundings can be viewed as a ‘dressed’ quasiparticle with renormalized mass and other dynamic properties. The lack of screening enables strong Coulomb interactions between charged particles, leading to new collective dynamics. In this talk, I will discuss three examples concerning strongly interacting quasiparticles in graphene. In the first example, it will be shown that the thermally populated electrons and holes to realize Dirac fluid, where a huge violation of Wiedemann-Franz law is observed. The second example is realizing magnetoexcitons to correlated quasiparticles in quantized Landau levels to form magnetoexcitons, which can condense into Bose-Einstein condensation. Finally, we will also discuss another way of correlated quasiparticles in graphene using superconducting proximity effect. Here, we employ the crossed Andreev reflection across thin Type II superconducting electrodes to correlated spatially separated quasiparticles. Under strong magnetic fields, the quantum Hall edge states can carry these quasiparticles.
Apr 14, 2017 · 1:45 p.m.– 2:45 p.m. · PCTS Seminar Room
Apr 17, 2017 · 12:00 p.m.– 1:00 p.m. · Joseph Henry Room
Apr 17, 2017 · 1:15 p.m.– 2:30 p.m. · Jadwin A06
HET Seminar | Eva Silverstein, Stanford University | “Six Point String Scattering: Simulation of Horizon Infallers”
Apr 17, 2017 · 2:30 p.m.– 3:30 p.m. · Bloomberg Lecture Hall - Institute for Advanced Study
Apr 20, 2017 · 8:00 p.m.–11:00 p.m. · McDonnell A02
"Exploding Stars, Dark Energy, and the Accelerating Cosmos"
HET Seminar | Mirjam Cvetic, University of Pennsylvania | “Continuous and Discrete Gauge Symmetries in F-Theory”
Apr 21, 2017 · 1:45 p.m.– 2:45 p.m. · Bloomberg Hall of Physics Library - Institute for Advanced Study
We present recent developments in F-theory compactifications and focus on advances in constructions of globally consistent F-theory compactifications with Abelian and discrete gauge symmetries, emphasizing technical advances and insights into higher-rank gauge symmetries. We also present recent studies of the origin of Abelian and discrete symmetries in Heterotic/F-theory duality. Furthermore, a new construction of Type IIB compactification with non-Abelian discrete gauge symmetry is highlighted.
Apr 24, 2017 · 12:00 p.m.– 1:00 p.m. · Joseph Henry Room
Apr 24, 2017 · 2:30 p.m.– 3:30 p.m. · PCTS Seminar Room
Apr 27, 2017 · 4:00 p.m.– 5:00 p.m. · Jadwin A10
Apr 28, 2017 · 1:45 p.m.– 2:45 p.m. · PCTS Seminar Room
May 2, 2017 · 4:00 p.m.– 5:30 p.m. · Jadwin 303
Donald R. Hamilton Lecture - Charles Kane, University of Pennsylvania; "Topological Phases of Matter"
May 4, 2017 · 8:00 p.m.– 9:30 p.m. · McDonnell A02
Matter can arrange itself in the most ingenious ways. In addition to the solid, liquid and gas phases that are familiar in classical physics, quantum mechanics enables the existence of electronic phases of matter that can have both exotic and useful properties. In the last century, the thorough understanding of the simplest quantum electronic phase - the electrical insulator - enabled the development of the solid state electronics technology that is ubiquitous in today's information age. In the present century, new "topological" electronic phases are being discovered that may enable future technologies by allowing the seemingly impossible to occur: indivisible objects, like an electron or a quantum bit of information, can be split into two, allowing mysterious features of quantum mechanics to be harnessed. Our understanding of topological phases, which was celebrated by the 2016 Nobel Prize in physics, builds on deep ideas in mathematics. We will try to convey that they are as beautiful as they are fundamental.
May 15, 2017 · 1:15 p.m.– 2:30 p.m. · PCTS Seminar Room