Seminar by Anshuman Bhardwaj

 

Speaker:  Anshuman Bhardwaj, LSU

Place: The Cloud

Date: Thursday Oct 21st

Time: 11am Central.

Zoom Link

https://lsu.zoom.us/j/6541089114

Title:  Inflationary dynamics and particle production in a toroidal Bose-Einstein condensate

Abstract:

Abstract: We present a theoretical study of the dynamics of a Bose-Einstein condensate (BEC) trapped inside an expanding toroid that can realize an analog inflationary universe. As the system expands, we find that phonons in the BEC undergo redshift and damping due to quantum pressure effects, owing to the thinness of the ring. We predict that rapidly expanding toroidal BEC’s can exhibit spontaneous particle creation, and study this phenomenon in the context of an initial coherent state wave function. We show how particle creation would be revealed in the atom density and density correlations, and discuss connections to the cosmological theory of inflation.

Bio

Anshuman is a PhD student at LSU, working under the supervision of Prof. Dan Sheehy on condensed matter theory

Seminar by José Polo-Gómez

 

Thursday, Sep 23, 2021

 

Speaker:  José Polo-Gomez, University of Waterloo

Place: The Cloud

Date: Thursday Sep 23nd

Time: 11am Central.

Zoom Recording

https://lsu.zoom.us/rec/share/zIGa7cH6Dj0oAVfoIBtLp0saGzH-tnwchFDthsOzDQ6uweaHW62E2Lo8rNnxvALZ.l6yusuS27FCfnc3S 

Title: A detector-based measurement theory for quantum field theory

Abstract:

Abstract: Any physical theory needs to describe how observers gather information about the modelled systems, i.e., needs to describe measurements. In 1993, Rafael Sorkin pointed out that idealized measurements, as used in non-relativistic quantum mechanics, cannot be applied in relativistic quantum field theory, since the corresponding update leads to causality violations. This left quantum field theory without a measurement theory.

 

In this seminar, we will review the previous approaches to the problem, like the Fewster-Verch framework. Then, we will introduce particle detectors (like the Unruh-DeWitt detector) and review how they can be consistently used within QFT. After that, we will use them to propose a measurement theory for quantum fields, and to provide a relativistic analogue to the quantum mechanical Lüders update. Finally, we will argue that the measurement scheme along with the update rule that we propose have all the desirable characteristics of a proper measurement theory that can be applied to modeling measurements of relativistic quantum fields in experimental settings.

Bio

Jose is a PhD student at the University of Waterloo, working under the supervision of Prof. Eduardo Martin-Martinez on aspects of relativistic quantum information

Seminar by Ivan Agulló

Speaker: Ivan Agulló, LSU

Place: The Cloud

Date: Thursday July 29th

Time: 12pm Central.

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Recorded lecture.

Title: Stimulated Hawking effect on an Optical White-Black Hole

Abstract:

In this informal talk I’ll summarize my recent work 2107.10217 with A. Brady and D. Kranas, on which we study the Hawking effect in optical systems containing the analog of a pair white-black hole. Our work contains a synergistic combination of analytical and numerical methods. Our analytical treatment is based on techniques from quantum Gaussian information, and it provides a simple and efficient model to describe all aspects of the out state, including the entanglement between any bi-partition. These tools allow us to analyze for the first time subtle aspects of the Hawking process, like the influence that ambient thermal noise and detector inefficiencies have on the out state. We find that aspects of the Hawking effect that are of quantum origin, i.e.\ quantum entanglement, are extremely fragile to the influence of inefficiencies and noise. More importantly, we propose a protocol to amplify and observe these quantum aspects, based on seeding the process with a single-mode squeezed input. Our ideas open the door to new possibilities of experimental verification of the Hawking effect.

Seminar by Francesco Sartini

 

Speaker: Francesco Sartini, ENS Lyon

Place: The Cloud

Date: Thursday July 22nd

Time: 12pm Central.

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https://lsu.zoom.us/j/6574388959

Title: Black Hole interior: Symmetries and regularization

Abstract:

The spacetime in the interior of a black hole can be described by an homogeneous line element, for which the Einstein–Hilbert action reduces to a one-dimensional mechanical model. We have shown that this model exhibits a symmetry under the (2+1)-dimensional Poincaré group. The existence of this symmetry provides a powerful criterion to discriminate between different regularization and quantization schemes. It also unravels new aspects of symmetry for black holes, and opens the way towards a rigorous group quantization of the interior. Remarkably, the physical ISO(2,1) symmetry can be seen as a broken infinite-dimensional symmetry. This is done by reinterpreting the action for the model as a geometric action for the BMS3 group, where the configuration space variables are elements of the algebra bms3 and the equations of motion transform as coadjoint vectors.

Seminar by Hongguang Liu

Speaker: Honggang Liu, FAU Erlangen

Place: The Cloud

Date: Thursday January 14th

Time: 12pm Central.

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https://lsu.zoom.us/j/96989058282

Title: Improved Effective Dynamics of Loop-Quantum-Gravity Black Hole and Nariai Limit

Abstract: We propose a new model of the spherical symmetric quantum black hole in the reduced phase space formulation. We deparametrize gravity by coupling to the Gaussian dust which provides the material coordinates. The foliation by dust coordinates covers both the interior and exterior of the black hole. After the spherical symmetry reduction, our model is a 1+1 dimensional field theory containing infinitely many degrees of freedom. The effective dynamics of the quantum black hole is generated by an improved physical Hamiltonian 𝐇 where the holonomy correction is implemented by the 𝜇-bar-scheme regularization with a Planckian area scale Δ (which often chosen as the minimal area gap in Loop Quantum Gravity). The effective dynamics recovers the semiclassical Schwarzschild geometry at low curvature regime and resolves the black hole singularity with Planckian curvature. Our model predicts that the evolution of the black hole at late time reaches the charged Nariai geometry dS2xS2 with Planckian radii. The Nariai geometry is stable under linear perturbations but may be unstable by nonperturbative quantum effects. Our model suggests the existence of quantum tunneling of the Nariai geometry and a scenario of black-hole-to-white-hole transition. During the transition, the linear perturbations exhibit chaotic dynamics with Lyapunov exponent 𝜆=2𝜋𝑇∼1/Δ relating to the Hawking temperature T of dS2. In addition, the Nariai geometry in our model provides an interesting example of Wheeler's bag of gold and contains infinitely many infrared soft modes with zero energy density. These infrared modes span a Hilbert space carrying a representation of 1-dimensional spatial diffeomorphisms (or the Witt/Virasoro algebra). The spatial diffeomorphisms are conserved charges of the effective dynamics by 𝐇.

Seminar by Anupam Mazumdar

 

Speaker: Anupam Mazumdar, University of Groningen
Place: The Cloud

Date: Tuesday, December 15th

Time: 9am

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https://lsu.zoom.us/j/6574388959?pwd=UlVxUzYrUHMvSW1GVUswSjVJc2I0QT09

Title: Witnessing Quantum gravity in a laboratory via miniaturist quantum accelerator

Abstract: Unveiling the nature of spacetime remains one of the final frontiers of modern theoretical physics. I will discuss how to witness the quantum nature of gravity in a table-top experiment by creating the right witness involving the two neutral masses (spin embedded) undergoing through the Stern-Gerlach apparatus. I will discuss various challenges involved in pursuing the dream of witnessing graviton and the critical challenges. There are many challenges to be met and I will discuss the important ones: (1)  To create a macroscopic quantum superposition of heavy masses via the Stern-Gerlach setup while controlling the stray gravitational acceleration and the gravity gradient noise, (2) Precise constraints on the magnetic field/current such that various electromagnetic interactions are under control, (3) Vacuum dominated Casimir effect which will create the main background for the experiment, (4) Constraints on vacuum and temperatures, (5) Feasibility of the experiment in a drop-tower, (6) The material properties and patch potentials. I will briefly discuss time scales for realising such an accelerator which will witness for the first time the graviton in a terrestrial laboratory.

Audio+Slides of the talk (.mp4) (500mb)

Subtitles (.vtt) (80kb)

Speaker: Alejandro Corichi, UNAM Morelia.

Place: Via Zoom.

Date: Thursday, March 19th.

Time: 10am

Title: TBA