Studying nature directly from fundamental degrees of freedom is often computationally limited by 

physical characteristics of exponentially growing configuration (Hilbert) spaces with particle number 

and signal-to-noise problems. This leaves many systems of interest to nuclear and particle physics 

intractable for known algorithms with current and foreseeable classical computational resources. By 

leveraging their natural capacity to describe entangled many-body states, the use of quantum systems 

themselves to form a computational framework is envisioned to be advantageous.  In this talk, I will 

share a developing perspective on the entanglement structure of quantum fields and discuss implications 

for their efficient simulation on quantum computational architectures. 

A large number of Majorana fermions with interactions coupling four of them at a time can exhibit interesting quantum dynamics. Models of this kind include the Sachdev-Ye-Kitaev (SYK) model, where the coefficients of quartic interactions are randomly distributed, and the Tensor models, where they respect continuous symmetries. These models exhibit approximate invariance under scaling of the time and have power law fall-off of the correlation functions.

In this talk we will discuss a pair of SYK or Tensor models coupled by the quartic interactions, and show that they produce a richer set of phenomena. These include a line of fixed points, where critical exponents vary along the line and formally acquire imaginary parts outside it. For one sign of the coupling constant, the approximate scale invariance continues to hold. For the other, a gap opens in the energy spectrum, resulting in exponential fall-off of correlation functions. This is indicative of breaking of a discrete symmetry. Thus, our quantum mechanical model exhibits dynamical phenomena characteristic of higher dimensional quantum field theories. Furthermore, the gapped phase of our model may be dual to a certain traversable wormhole in two-dimensional space-time.

The talk will end with a similar discussion of a pair of complex SYK models coupled by a quartic interaction which preserves the U(1) x U(1) symmetry. For a range of parameters, this model gives rise to breaking of one of the U(1) symmetries. This is demonstrated via an analysis of the large N Dyson-Schwinger equations, as well as by Exact Diagonalizations of the finite N Hamiltonians.

Zoom link : https://uky.zoom.us/j/97553578130

Recording: https://uky.zoom.us/rec/play/rTWoRCvq8JEfgyyhHKGAlcV2a6XRi8DwaILPRPBY_Y…-?continueMode=true

Abstract :  The inflationary scenario has become the standard

paradigm of early universe cosmology, but it is not

the only scenario which can explain the currently

available data on the large-scale structure of the

universe. I will compare inflation with two alternative

scenarios, the "Ekpyrotic bounce" scenario, and

"String Gas Cosmology". I will then argue that

there are severe obstacles to embed inflationary

cosmology into quantum gravity, and that the

alternative scenarios may be more promising"  

Zoom link: https://uky.zoom.us/j/94475622713

Recording: https://uky.zoom.us/rec/play/uZcvJryspjM3T4aRtASDVvIvW42-La6sh3IZ_aUEn0…

In the past decade, renewed interest in the nucleon electromagnetic form factors was sparked by new measurements of electron-proton scattering at low Q^2 by the A1 Collaboration and of the proton charge radius in muonic hydrogen by the CREMA Collaboration. Subsequent theoretical developments re-examined longstanding assumptions on the parameterizations of these form factors. In this talk, I will review some of these developments, then present new parameterizations of the form factors that are the result of work in the past few years. Finally, I will outline applications of these form factors in both atomic physics and for the US program of precision neutrino measurements.

Recorded talk and slides: https://www.dropbox.com/sh/sek9spcry22xorw/AABHxLmJwsrae-E0zEftz7HWa?dl=0

We consider a massive scalar, neutral, field theory in a five dimensional flat spacetime. Subsequently, one spatial dimension is compactified on a circle, $S^1$, of radius R. The resulting theory is defined in the manifold, $R^{3,1}\otimes S^1$, consists of a states of lowest mass, $m_0$, and a tower of massive Kaluza-Klein states. The analyticity property of the elastic scattering amplitude is investigated in the frame works of Lehmann-Symanzik-Zimmermann formulation of this field theory. In the context of nonrelativistic potential scattering, for $R^3\otimes S^1$ spatial geometry, it was shown that the forward scattering amplitude does not satisfy analyticity for a class of potentials which might have important consequences if same attribute holds in relativistic quantum field theories. We address this issue with $R^{3,1}\otimes S^1$ geometry. We show that the forward scattering amplitude of the theory satisfying LSZ axioms does not suffer from lack of analyticity. The importance of the unitarity constraint is exhibited in displaying the properties of the absorptive part of the forward amplitude.

We argue that the SYK model leads to a three dimensional dual theory in a suitable background. At strong coupling, a Horava-Witten compactification of one of the dimensions reproduces the SYK spectrum, and a non-standard propagator of the 3D theory exactly reproduces the two point function of the bilocal fields. Furthermore, this three dimensional picture reproduces the leading finite coupling correction to the “zero mode” contribution. The space-time on which the bilocal fields live is not, however, the dual space-time in the sense of AdS/CFT duality – rather the bilocals are related to the dual fields by an integral transform.

The understanding of out-of-equilibrium physics, especially dynamic instabilities and phase transitions, is one of the major challenges of contemporary science. Focusing on non-equilibrium dynamics of open dissipative spin systems, I will introduce non-Hermitian Hamiltonian formalism, in which anti-Hermiticity reflects dissipation and presence of non-conservative forces. I will discuss a special case of parity-time-symmetric Hamiltonians that exhibit a phase transition from real to complex eigenspectrum, and how it manifests experimentally. I will then illustrate branch point singularities that appear in the spectrum of some non-Hermitian Hamiltonians, and show how these so-called exceptional points provide access to a wealth of topological effects unique to non-Hermitian systems, e.g. asymmetric transport and non-reciprocal time evolution.

I'll talk about the operator algebra view of entanglement and its connection to more down-to-earth calculational ways of understanding it. This talk will be a pedagogical introduction to the subject.

The interplay of symmetry and topology has been at the forefront of recent progress in quantum matter. In this talk I will discuss an unexpected connection between band topology and competing orders in a quantum magnet. The key player is the two-dimensional Dirac spin liquid (DSL), which at low energies is described by an emergent Quantum Electrodynamics with massless Dirac fermions (a.k.a. spinons) coupled to a U(1) gauge field. A long-standing open question concerns the symmetry properties of the magnetic monopoles, an important class of critical degrees of freedom. I will show that the monopole properties can be determined from the topology of the underlying spinon band structure. In particular, the lattice momentum and angular momentum of monopoles can be determined from the charge (or Wannier) centers of the corresponding spinon insulators. I will then discuss the consequences of the monopole properties, such as the stability of the DSL on different lattices, universal (experimental and numerical) signatures of DSL, and competing symmetry-breaking phases near the DSL state.