# Physics and Astronomy Colloquia, Academic Year 2017-2018

Colloquium committee: Leonardo Rastelli (Chair),  Marivi Fernandez-Serra, Eden Figueroa, Krishna Kumar, Mengkun Liu, Rosalba Perna, and Giacinto Piacquadio

Coffee & Tea served at 3:45 pm.

Talk begins at 4:15 pm.

Location: Harriman 137 (bottom of square C4 on the campus map)

 Jan. 23 Sally Dawson BNL and Stony Brook University Precision measurements for the LHC The discovery of the Higgs boson at the LHC in 2012 was a triumph for particle physics and demonstrated the basis correctness of the Glashow-Weinberg theory of weak interactions. I will discuss the next phase of our understanding of the mechanism of electroweak symmetry breaking at the LHC and how progress requires the delicate interplay of experiment and theory. Piacquadio Jan. 30 Peter Armitage  Johns Hopkins University On Ising's model of ferromagnetism The 1D Ising model is a classical model of great historical significance for both classical and quantum statistical mechanics. Developments in the understanding of the Ising model have fundamentally impacted our knowledge of thermodynamics, critical phenomena, magnetism, conformal quantum field theories, particle physics, and emergence in many-body systems. Despite the theoretical impact of the Ising model there have been very few good 1D realizations of it in actual real material systems. However, it has been pointed out recently, that the material CoNb2O6, has a number of features that may make it the most ideal realization we have of the Ising model in one dimension.  In this talk I will discuss the surprisingly complex physics resulting in this simple model and review the history of "Ising’s model” from both a scientific and human perspective.  In the modern context I will review recent experiments by my group and others on CoNb2O6.  In particular I will show how low frequency light in the THz range gives unique insight into the tremendous zoo of phenomena arising in this simple material system. Liu Feb. 6 Jim Lattimer Stony Brook University GW170817 and the History of the R-Process The binary neutron star merger GW170817 represents a triumph of not only astrophysics observations, but also astrophysical theory and computation.  Gravitational waves observed on Aug. 17, 2017, from the direction of the constellation Hydra indicated a merger of two neutron stars at a distance of 40 Mpc.  Gamma-ray observatories found an associated short, hard gamma-ray burst probably produced by a jet formed in the aftermath of the formation of a rotating black hole. More than 70 optical observatories tracked an associated kilonova on the outskirts of the galaxy NGC 4993 from relativistically ejected matter illuminated by the radioactivity of its newly-formed heavy nuclides.  X-ray telescopes and radio observatories are still monitoring the shocked ejecta.  All these observations had been predicted as the prototypical example of multi-messenger astronomy, the subject of dozens of conferences and intensive computations for many years.  New limits to the equation of state of dense matter have been established.  But perhaps even more importantly, the long-standing riddle of the primary source of the r-process, which is responsible for the creation of most isotopes of all natural elements heavier than zirconium (Z=40), seems to have been solved. Although decompressing neutron star matter had been proposed as the r-process source 44 years ago, it was not until the last few years that this idea gained favor.  I will review the observations and theory behind this remarkable event. Perna Feb. 13 Thomas Hartman Cornell University Black Holes, Time Machines, and Critical Phenomena Black holes, aside from their importance in astrophysics, play a crucial role in understanding quantum field theory. I will outline how holographic duality is used to map black hole dynamics to properties of more down-to-earth physical systems and strongly correlated materials. Then, I'll describe how a fundamental limit on quantum gravity --- causality in curved spacetime --- has led to new insights in strongly coupled matter, including new predictions for the 3D Ising model, which governs ferromagnets and the liquid-vapor critical point. Rastelli Feb. 20 Bruce A. Remington NIF Discovery Science Program Leader Lawrence Livermore National Lab Exploring the universe through the  Discovery Science program on NIF New regimes of science are being experimentally studied at high energy density (HED) facilities around the world, spanning drive energies from microjoules to megajoules, and time scales from femtoseconds to microseconds. The ability to shock and ramp compress samples to very high pressures and densities allows new states of matter relevant to planetary and stellar interiors to be studied. Shock driven hydrodynamic instabilities evolving into turbulent flows relevant to the dynamics of exploding stars (such as supernovae), accreting compact objects (such as white dwarfs, neutron stars, and black holes), and planetary formation dynamics (relevant to the exoplanets) are being probed. The dynamics of magnetized plasmas relevant to astrophysics, both in collisional and collisionless systems, are starting to be studied. High temperature, high velocity interacting flows are being probed for evidence of astrophysical collisionless shock formation, the turbulent magnetic dynamo effect, magnetic reconnection, and particle acceleration. And new results from thermonuclear reactions in hot dense plasmas relevant to stellar and big bang nucleosynthesis are starting to emerge. A selection of examples providing a compelling vision for frontier science on NIF in the coming decade will be presented. Perna Feb. 27 Carter Hall University of Maryland Down-to-earth searches for cosmological dark matter with LUX and LZ A laboratory detection of the Milky Way's dark matter halo would be a spectacular confirmation of modern cosmology. It would also fundamentally extend the standard model of particle physics. The LUX experiment searched for dark matter interactions in an underground particle detector in South Dakota between 2013 and 2016. No evidence was found for the existence of 'Weakly Interacting Massive Particles' (WIMPs).  This result and recent results from the Xenon1T and PandaX-II experiments set stringent constraints on the properties of these hypothetical particles. I will review these results, and also describe the status of the LZ experiment, which will explore another factor of 100 in cross-section parameter space starting in 2020. Kumar March 6 Kevin Dusling  APS Physical Review Letters, The Inside Story Physical Review Letters is the most cited journal in physics, with a Letter cited roughly every 80 seconds.  Editors decide what to publish with extensive input from peer review and consultation with the PRL editorial board.  This talk will provide an outline of how PRL manages the review of more than 10,000 annual submissions, less than 1/4 of which are published, while maintaining the breadth and exclusivity that is the hallmark of the journal. We face many challenges, however, as the publishing trends in some areas of physics shift, for example to smaller, less comprehensive, or more interdisciplinary venues.  I will discuss some of these challenges, and what PRL is doing, to maintain a competitive journal that best serves the physics community. Most importantly, I welcome your feedback during and after the talk. March 13 Spring Break: No classes and no colloquium March 20 Eden Figueroa Stony Brook University Building a room temperature quantum computer Quantum engineering is the design and testing of the novel devices needed to achieve quantum information communication and computing. Some of these fundamental components store and retrieve qubits (quantum memories), while others are geared towards their manipulation (quantum gates). Successfully interconnecting many of these devices is the key to construct the first generation of quantum computers and quantum-protected communication networks. In the first part of my talk I will show how to store, modify and distribute photonic qubits by optically manipulating the properties of room temperature atomic clouds. I will also describe our latest results regarding the construction of an elementary analog quantum computer capable of simulating Dirac relativistic dynamics using atoms and quantized light. In the second part I will present our recent experiments in which several quantum devices are already interconnected forming one of the largest quantum processing networks in the world. Finally, I will discuss the prospects of this unique system to serve as both a long-distance quantum cryptographic communication network and a programmable light-based quantum computer. March 27 Mehran Kardar MIT Force from non-equilibrium fluctuations in QED and Active Matter The pressure of a gas, the van der Waals attraction between molecules, and the Casimir force in quantum electrodynamic (QED) are classical examples of forces resulting from equilibrium (thermal or quantum) fluctuations. Current research on “Active Matter” studies collective behaviors of large groups of self-driven entities (living or artificial), whose random motions superficially resemble thermally fluctuating particles. However, the absence of time reversal symmetry leads to unusual phenomena such as directed (ratchet) forces, and a pressure that depends on the shape and structure of the confining wall. Some manifestations of QED fluctuations out of thermal equilibrium are well-known, as in the Stefan-Boltzmann laws of radiation pressure and heat transfer. These laws, however, acquire non-trivial twists in the near-field regime of sub-micron separations, and in the proximity of moving surfaces. I will discuss dissipation in moving steady states, and the non-Gaussian fluctuations of a particle in a quantum bath. Fernandez-Serra April 3 Monica Olvera de la Cruz Northwestern University Attractions and Repulsions Mediated by Monovalent Salts High concentrations of monovalent salt can induce the solubilization or crystallization of NPs and proteins. By using a multiscale coarse-grained molecular dynamics approach, we show that, due to ionic correlations in the electrolyte NPs at high monovalent salt concentrations interact via remarkably strong long-range attractions or repulsions, which can be split into three regimes depending on the surface charge densities of the NPs. NPs with zero to low surface charge densities interact via a long-range attraction that is stronger and has a similar range to the depletion attraction induced by polymers with radius of gyrations comparable to the NP diameter. On the other hand, moderately charged NPs with smooth surfaces interact via a strong repulsion of range and strength larger than the repulsion predicted by models that neglect ionic correlations, in agreement with recent experimental observations. Interactions between strongly charged NPs (>2 e/nm2) show an attractive potential well at intermediate to high salt concentrations, which demonstrates that electrolytes can induce aggregation of strongly charged NPs. We discuss the relation of our results to the physical properties of concentrated electrolytes in bulk and in confinement, and the consequence of such correlations to the assembly of DNA functionalized nanoparticles. Fernandez-Serra April 10 Edward Shuryak Stony Brook University The quest for Quark-Gluon Plasma The first half of the talk reviews historical evolution of hot QCD and  heavy ion collisions. It will remind the main observations, since  2000 at Relativistic Heavy Ion Collider in BNL and, since 2010, at Large Hadron Collider at CERN, together with theory developments. All of that resulted in demonstration that QGP is a strongly coupled plasma, with rather  unusual kinetic properties. The mean free path, deduced from its  viscosity and jet quenching parameter \hat q, is much smaller than that given by perturbative estimates, especially close to the phase transition temperature T_c.  The second half of the talk is devoted to theoretical ideas to explain that, by the observation that QGP is in fact a dual plasma, containing both electric" quasiparticles, quarks and gluons, as well as  magnetic monopoles.  The role of monopoles is maximal near T_c, at T