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# Upcoming

in 4 days

Sebastian Erne
# QSimFP FVD Seminar: Presentation on extracting effective field theory descriptions from cold atoms experiments (Title to follow)

Abstract and Bio to follow. Sebastian Erne is from TU Wien

https://zoom.us/j/97690810408
in 45 days

TBA
# QSimFP QBH Seminar: TBA

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# QSimFP FVD Seminar: TBA

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# QSimFP QBH Seminar: TBA

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# QSimFP FVD Seminar: TBA

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# QSimFP QBH Seminar: TBA

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# QSimFP FVD Seminar: TBA

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# To be announced

# Past seminars

11 days ago

Markus Oberthaler
# Quantum field simulator for dynamics in curved spacetime

"In this seminar I will introduce the capabilities of ultracold gases to address fundamental questions in quantum field theory. I will introduce the experimental capabilities in preparation and detection of quantum fields in atomic gases. A special focus will be on our latest result on the implementation of curved spacetime for a scalar massless quantum field. We have shown that positive as well as negative curvature can be experimentally realized and can be dialed in as needed. We also used the experiment/simulator to reveal particle production in an accelerating, decelerating and constantly expanding spacetime. Employing Sakharov oscillations for detecting the production of excitations opens a window to add to the power spectrum also phase information about the excitations."
Markus Oberthaler is a professor, chair of experimental physics at Kirchhoff-Institute for Physics,Heidelberg University. His main research fields are Quantum Entanglement in many particle systems and quantum simulation, precision experiment testing quantum field theory, quantum metrology, immersed quantum systems, universal physics far from equilibrium and connection to high energy physics, environmental physics and dating of water and ice with Argon Trap Trace Analysis (ATTA).

59 days ago

Jonathan Braden
# The Role of Short-Wavelength Modes in Vacuum Decay

ABSTRACT
False vacuum decay plays an important role in many cosmological
scenarios, while also acting as an important keystone model for
nonequilibrium quantum field theory. It was recently realized that
dilute gas Bose-Einstein condensates (BECs) can be used to emulate the
dynamics of relativistic vacuum decay, providing a unique experimental
window into the early Universe. Making optimal use of these experiments
requires a detailed understanding of the theoretical predictions for
vacuum decay.
I will discuss some recent work on the role of short-wavelength
fluctuations in real-time simulations of false vacuum decay, focussing
on the case of pure scalar field theory. This includes renormalization
effects, which capture averaged effects of fluctuations on the
long-wavelength dynamics, as well as stochastic contributions where the
long-wavelength modes are sensitive to the particular realization of the
short-wavelengths. I will comment on the implications of these results
for BEC experiments. Finally, time (and audience interest) permitting,
I will discuss how the evolution of a dilute gas BEC system can be
mapped onto another important nonlinear epoch in the early Universe ---
the end-of-inflation.
BIO
Jonathan Braden is a Senior Research Associate at the Canadian Institute
for Theoretical Astrophysics. His primary research interest is early
Universe cosmology, with a particular focus on strong nonlinearity in
the early Universe. Some specific topics include the dynamics of phase
transitions, (p)reheating, and particle production during inflation; and
the nonGaussian imprints of these phenomena in observational data. He is
also interested in using analog early Universe experiments to build a
"Universe on a table-top". He also has extensive experience in high
performance computing, specifically the application of spectral and
symplectic integration schemes to cosmology. He was previously a
postdoctoral fellow at University College London. He received his PhD
in Physics from the University of Toronto.

171 days ago

Ulrich Schneider (Department of Physics, University of Cambridge, UK)
# Realizing a first-order quantum phase transitions in a driven optical lattice

ABSTRACT: Phase transitions and critical phenomena have been at the heart of many-body physics, and quantum simulations with cold atoms from the beginning. While almost all phase transitions in cold atoms systems are continuous, there is a renewed interest also in discontinuous (first-order) phase transitions and the quantum metastability, whose relativistic analogues are believed to play an important role in early-universe cosmology (false vacuum decay).
We experimentally demonstrate a novel level of control over a quantum phase transition by combining an optical lattice with an uncommon type of Floquet engineering based on a resonant drive. Contrary to most applications of periodic driving, where the drive frequency is selected to avoid all resonances, we resonantly couple the lowest two bands of a lattice. With this drive, we can not only induce the superfluid to Mott insulator transition but are furthermore able to control its character and turn the Mott transition from a continuous into a discontinuous transition, thereby opening the door to quantum simulations of the early universe and interacting topological transitions in condensed matter systems.
BIO: Prof. Ulrich Schneider is a Professor of Many-Body Physics at the University of Cambridge. His work is centred on employing ultracold atoms in optical lattices as a testbed to study Quantum Many-Body Dynamics. His scientific interests range from quantum thermodynamics, low-dimensional systems, and strongly correlated systems to topological effects and many-body localization.
Prof. Schneider studied physics in Kaiserslautern and Sheffield, received his PhD from the Johannes-Gutenberg University Mainz, and worked as a senior scientist at the Ludwig-Maximilians-University (LMU) and the Max-Planck-Institute for Quantum Optics (MPQ) in Munich.
He is a fellow of Jesus College, received the 2015 Rudolf-Kaiser Prize, and the recipient of ERC Starting (2016, Quasicrystal) and Consolidator (2021, Kagome) grants. In 2020 he also joined the AION collaboration building an Atom Interferometer and Observatory Network.
The seminar will last 1 hour including Q&A and be held at 3.00pm UK Time/10.00am Toronto Time.
This seminar will be held on Zoom.

199 days ago

Ian Moss
# False vacuum decay in an ultracold spin-1 Bose gas

Abstract:
After some background on first order transitions in the early universe
I’ll describe a new physical system that might be used as a
laboratory analogue. The system is based on a spin 1 Bose gas
with Raman and RF induced interactions. It does not require
the Feshbach resonance and modulated interactions
of previous proposals. Based on work by Ian Moss, Tom Billam
and Kate Brown.
Biosketch:
Ian Moss is Professor of Theoretical Cosmology at Newcastle University.
He has been been researching early universe phase transitions for what
seems like forever and he is half of the Hawking-Moss instanton.
The seminar will last 1 hour including Q&A and be held at 3.00pm UK Time/10.00am Toronto Time.
This seminar will be held on Zoom.

214 days ago

Maxime Jacquet
# Quantum vacuum excitation of a quasi-normal mode in an analog model of black hole spacetime

Maxime Jacquet (Laboratoire Kastler Brossel,Quantum Optics Group, Paris, France), on "Quantum vacuum excitation of a quasi-normal mode in an analog model of black hole spacetime"
Biosketch: Maxime is currently leading experimental and theoretical research in analogue gravity with quantum fluids of light in the Quantum Optics group at Laboratory Kastler Brossel, Sorbonne University and CNRS, France.
Abstract:
Analogue gravity enables the laboratory investigation of effects of quantum field theories on curved spacetimes. The archetypal example is the parametric amplification of vacuum quantum fluctuations of the field on the curved spacetime, as in the Hawking effect (the correlated emission of waves) at the event horizon.
In this talk, I will review theoretical work on the Hawking effect in transsonic, quantum fluids of microcavity polaritons [1]. Because of the driven-dissipative dynamics of the fluid, the system is out of thermal equilibrium. I will explain how this impacts correlated emission by the Hawking effect [2], and also show that dissipation may be harnessed to observe novel effects like the quantum vacuum excitation of quasi-normal modes of the acoustic field [3]. This, I will argue, opens a range of new questions pertaining to all quantum fields on black hole spacetimes beyond analogue models.
Refs: [1] arxiv:2002.00043, [2] arxiv:2201.02038, [3] arxiv:2110.14452.
The seminar will last 1 hour including Q&A and be held at 3.00pm UK Time/10.00am Toronto Time.
This seminar will be held on Zoom.

227 days ago

Dalila Pirvu
# Bubble Clustering in Cosmological First Order Phase Transitions

Abstract: False vacuum decay in quantum mechanical first order phase transitions is a phenomenon with wide implications in cosmology and presents interesting theoretical challenges. In the standard approach, it is assumed that false vacuum decay proceeds through the formation of bubbles that nucleate at random positions in spacetime and subsequently expand. In our work, we investigated the presence of correlations between bubble nucleation sites using a recently proposed semiclassical stochastic description of vacuum decay. The procedure sampled vacuum fluctuations which were evolved using classical lattice simulations. We computed the two-point function for bubble nucleation sites from an ensemble of simulations, demonstrating that nucleation sites cluster in a way that is qualitatively similar to peaks in random Gaussian fields. I will comment qualitatively on the phenomenological implications of bubble clustering in early Universe phase transitions, which include features in the power spectrum of stochastic gravitational waves and an enhancement or suppression of the probability of observing bubble collisions in the eternal inflation scenario. I finish by explaining briefly how our results can be tested empirically using a table-top analogue of vacuum decay.
Biosketch: Dalila Pirvu is a second year PhD student at the Perimeter Institute and University of Waterloo in Canada. She did her undergraduate at Imperial College London. Her work is focused on dynamical lattice simulations of phase transitions in quantum field theories.
The seminar will last 1 hour including Q&A and be held at 3.00pm UK Time/10.00am Toronto Time.
This seminar will be held on Zoom. Details to follow

242 days ago

Niayesh Afshordi
# Stimulating Hawking Radiation of Gravitational Waves

Abstract: I will outline the diverse theoretical arguments for why quantum mechanics of merging black holes should lead to the stimulation of Hawking Radiation of gravitational waves, which may manifest as delayed echoes in observations. I will then summarize the status and outlook of the observational program to search for these echoes.
Biosketch: Niayesh Afshordi is an Astrophysicist whose research spans from Early Universe Cosmology and Quantum Gravity, to Dark Matter, Dark Energy, Extragalactic Astronomy, Large Scale Structure of the Universe, and High Energy Astrophysics. He received his PhD at Princeton in 2004. He then did postdocs at Harvard College Observatory and Perimeter Institute for Theoretical Physics. He is currently a professor of Physics and Astronomy at the University of Waterloo. He is also an associate faculty at Perimeter Institute, and a founding faculty of the Waterloo Centre for Astrophysics.
The seminar will last 1 hour including Q&A and be held at 3.00pm UK Time/10.00am Toronto Time.
This seminar will be held on Zoom.

277 days ago

Maria Chiara Braidotti
# Measurement of Penrose superradiance in a photon fluid

Superradiance is the amplification ofwaves scattered by a rapidly rotating object, first proposed by Roger Penroseas a way to extract energy from rotating black holes. Despite being afundamental process in wave physics, astrophysical superradiance has not beenobserved yet due to the large distances involved. However, proposal based onanalogue gravity studies have demonstrated their versatility providing the firstmeasurement of superradiance in a hydrodynamic experiment.
Here we report the first measurementof Penrose superradiance in nonlinear optical systems, especially in a 2Dsuperfluid. A weak signal beam with orbital angular momentum is focused ontothe core of a pump vortex. In the scattering, a negative norm idler wave isgenerated and trapped inside the pump core, while the signal (positive normwave) gets amplified. Our results demonstrate the presence of Penrosesuperradiance in superfluids unveiling the key role of the negative norm modein the amplification process.
Maria Chiara Braidotti is a research associateat the School of Physics & Astronomy of the University of Glasgow (UoG),Scotland. She joined works in the ExtremeLight group lead by Prof. Faccio, UoG(http://www.physics.gla.ac.uk/XtremeLight/index.html). Her main expertise is theoretical andexperimental nonlinear optics, especially using it as a tool to testfundamental processes at the interface between gravitation and quantummechanics. In recent years, her research activity has focused on the test ofPenrose process and Zel’dovich effect both involving amplification ofelectromagnetic modes from the scattering with a rotating body.
She is author of more than 15 publications ininternational journals (with 2 publications on Physics Review Letters journal)and over 30 invited presentations to national and international conferences.