Physics Department Colloquia

Spring 2018 Schedule

All talks will be in the Physics Department Library (accessed from 3438 Ingersoll Hall) unless otherwise stated.

Check for updates to the schedule as the semester progresses.

Thursday, March 15, 12:30 p.m.

Speaker: Jillian Bellovary, Department of Physics, Queensborough Community College, CUNY

Title: Multimessenger Signature of Massive Black Holes in Dwarf Galaxies

Abstract: Inspired by the recent discovery of several nearby dwarf galaxies hosting active galactic nuclei, I will present results from a series of cosmological hydrodynamic simulations focusing on dwarf galaxies which host supermassive black holes (SMBHs). Cosmological simulations are a vital tool for predicting SMBH populations and merger events which will eventually be observed by LISA. Dwarf galaxies are the most numerous in the universe, so even though the occupation fraction of SMBHs in dwarfs is less than unity, their contribution to the gravitational wave background could be non-negligible. I find that electromagnetic signatures from SMBH accretion are not common among most SMBH-hosting dwarfs, but the gravitational wave signatures can be substantial. The most common mass ratio for SMBH mergers in low-mass galaxy environments is ~1:20, which is an unexplored region of gravitational waveform parameter space. I will discuss the occupation fraction of SMBHs in low-mass galaxies as well as differences in field and satellite populations, providing clues to search for and characterize these elusive giants lurking in the dwarfs.

Monday, April 9, 3:30 p.m. in Ingersoll 3428

Speaker: Paul Winterbotham, Wolfram Research, Inc.

Title: Cross-discipline Mathematica and Wolfram|Alpha seminar

Abstract: I like to begin with a technical overview of Mathematica, as well as briefly touching on the creation of Wolfram|Alpha. Next, we can discuss emerging trends in technology and what is currently available (or being developed) to support those trends. Then, to give you a sense of what's possible, I'll discuss how other organizations use these tools for teaching and research.

Thursday, April 19, 12:30 p.m.

Speaker: Steven Vallone, Department of Physics, Brooklyn College, CUNY

Title: A Colloquium in Two Parts: 1) Navigating the Physics Doctoral Program at CUNY, 2) An Exploration of Spin Crossover Compounds as Barocaloric Materials

Abstract: This talk will be given in two parts: in the first, aimed at the advanced undergraduate student contemplating a graduate program in physics, I will discuss my experience as a doctoral student at CUNY and the PhD experience in general, including a focus on day-to-day activity. I will also touch on some of the logistics involved in navigating the application and bureaucratic processes. In the second portion of this talk, I will discuss my own research on spin crossover compounds and their potential application as barocalorics. Spin crossover occurs primarily in an organometallic compound wherein the ligand field centered around the d electron shell splits the subshell’s energy levels further and, in the presence of some external field, causes the electron filling behavior to violate Hund’s rules yielding a new spin state and a first-order phase transition. Barocalorics have gained much attention lately due to their thermodynamic properties and flexibility in terms of raw materials, and spin crossover compounds present another avenue towards efficient cooling devices.

Wednesday, May 2, 3:30 p.m.

Speaker: Sarang Gopalakrishnan, College of Staten Island, CUNY

Title: Entanglement and chaos in some simple interacting quantum systems

Abstract: We introduce and describe a class of simple facilitated quantum spin models in which the dynamics is due to the repeated application of unitary gates. The dynamics of the models we discuss can be classically simulated, and their eigenstates classically constructed (although they are highly entangled). We consider a variety of models in both one and two dimensions, involving Clifford gates and Toffoli gates. For some of these models, we explicitly construct conserved densities; thus these models are "integrable." The other models do not seem to be integrable; yet, for some system sizes and boundary conditions, their eigenstate entanglement is strongly subthermal. These models exhibit a parametric separation between the various time and length-scales associated with the emergence of irreversibility.

[1] https://arxiv.org/abs/1802.07729

Tuesday, May 15, 12:30 p.m.

Speaker: Viraht Sahni, Department of Physics, Brooklyn College, CUNY

Title: Schrödinger Theory of Electrons: New perspectives

Abstract: The temporal and stationary-state Schrödinger theory of electrons in external electric and magnetic fields can be described in a manner analogous to that of classical physics. This description is from the perspective of the individual electron. The corresponding equations of motion for each electron – the ‘Quantal Newtonian’ second and first laws – are in terms of ‘classical’ fields whose quantal sources are expectations of Hermitian operators taken with respect to the wave function. The fields are representative of electron correlations due to the Pauli exclusion principle and Coulomb repulsion, and of properties such as the electron density, and kinetic and magnetic effects. A consequence of the laws is that the Hamiltonian is a unique exactly known functional of the wave function. As such the Schrödinger equation is inherently self-consistent. This generalization leads to the self-consistent calculation of the wave function, to other insights, and to the determination of Hamiltonians of future human-made electronic systems. These ideas will be explicated by application to 2D ‘artificial’ atoms or quantum dots in a magnetic field in both a ground and first excited singlet state.