Seminar by Salvatore Ribisi Tues Feb 27th 2024

 

Speaker: Salvatore Ribisi

 

Place: The Cloud

Date: Tues Feb 27th

 

 
Time: 9am Central.

 

 

 

 

 

Zoom link

 

https://lsu.zoom.us/j/96858252540?pwd=a0x4anVBSG5aMUgzaWFPUnI4eVRqZz09

 

Title: Light-cone thermodynamics

 

Abstract: 

 

After a brief introduction of the previous works on Light-cone thermodynamics done by Perez and De Lorenzo, I will present the results of our last paper. Here, we explicitly express the Minkowski vacuum of a massless scalar field in terms of the particle notion associated with suitable spherical conformal killing fields. These fields are orthogonal to the light wavefronts originating from a sphere with a radius of rH in flat spacetime: a bifurcate conformal killing horizon that exhibits semiclassical features similar to those of black hole horizons and Cauchy horizons of spherically symmetric black holes. Our result highlights the quantum aspects of this analogy and extends the well-known decomposition of the Minkowski vacuum in terms of Rindler modes, which are associated with the boost Killing field normal to a pair of null planes in Minkowski spacetime (the basis of the Unruh effect). While some features of our result have been established by Kay and Wald's theorems in the 90s -- on quantum field theory in stationary spacetimes with bifurcate Killing horizons -- the added value we provide here lies in the explicit expression of the vacuum.

Pictures of the O'Connell workshop

 Pictures of the O'Connell Workshop, October 5-6 2023. Click on picture to enlarge.

Talk by Manasse Mbonye

Speaker:   Manasse Mbonye, ICTP-East African Institute for Fundamental Research, University of Rwanda, Kigali, Rwanda

Place: The Cloud

Date: Tuesday April 25th

Time: 9am Central.

Recording

Bio

AriXiv paper

Title:   Is cosmic dynamics self-regulating?

Abstract: 

We discuss a cosmological model for a universe with self-regulating features. We set up the theoretical framework for the model and determine the time evolution of the scale-factor a(t). It is shown that such a universe repeatedly goes through alternate periods of matter and dark energy domination. The resulting dynamics oscillates about the would-be ideal time-linear or coasting path, with monotonic expansion. When compared to dynamics of the observed physical Universe, the model recovers the observationally-established evolutionary features of the latter, from the big bang to the current acceleration, and farther. It suggests a universe that initially emerges from a non-singular state, associated with a non-inflationary acceleration, and which acceleration it exits naturally with matter-energy generation. The model does not have a horizon problem or a flatness problem. It reproduces the observed current values of standard cosmic parameters, including the age t0, the current Hubble parameter H0 and dark energy Ωde and matter Ωm density parameters. We find the dark matter density-profile generated by the model naturally leads to flat rotation curves in galaxy halos. The model is falsifiable. It makes predictions that can be tested, as suggested. Finally, we discuss the dimensionless age (H0t0 ' 1) paradox as an example of the model´s ability to address standing puzzles. The findings suggest dynamics of the physical Universe may be self-regulating and predictable.

Talk by Anthony Brady Wed Feb 2nd 2022

 

Speaker:   Anthony Brady

Place: The Cloud

Date: Wednesday Feb 2nd

Time: 11am Central.

Zoom Link

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

Title:   Entangled sensor-networks for dark-matter searches

Abstract: 

One of the most ambitious endeavors in human history is determining the material make-up of the cosmos. However, along this journey to discover the constituents of the universe, modern physics has led us to two mysterious entities which dominate cosmic structure: dark energy and dark matter. Dark matter (DM), for instance, comprises the majority of mass in galaxies and plays a crucial role in galaxy formation--- yet we have absolutely no idea what it is made of. It is currently believed that DM constituents lie outside of the standard model of particle physics, due to their (very) weak coupling to all known forms of normal matter, radiation etc., and a fervorous hunt for such exotic DM-particles has ensued over the last half-century. For example, terrestrial experiments with microwave cavities search for (light, bosonic) DM particles via their very weak coupling to the electromagnetic field, in which case a DM particle can convert to a cavity photon and the excess power can be read out. Unfortunately, this DM signal is extremely feeble, and thus delicate care, precise instrumentation, and exhaustively long experimental-runs are required to search for these illusive DM particles. Fortunately, quantum technologies can substantially help to relieve some of the experimental strain. In this talk, I will discuss how quantum squeezing can accelerate the search for DM particles (as was recently shown in experiment). I will further discuss how an entangled sensor-network--- consisting of many, entangled microwave cavities--- can further enhance the search for DM. This provides a beautiful example of the potential impact that near-term quantum technologies can have on fundamental physics and, on a more intimate level, our journey to understand the cosmos. 

Talk by Jaime Calderón-Figueroa

Speaker:  Jaime Calderón-Figueroa, The University of Edinburg

Place: The Cloud

Date: Thursday Dec 16th

Time: 11am Central.

Zoom Link

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

Title:  Universal signature of quantum entanglement across cosmological distances

Abstract: 

In this talk, I will discuss observable effects of primordial quantum entanglement between short- and long-wavelength scalar perturbations sourced during inflation. We point out that this is not just an extra assumption for a particular inflationary model, but rather an inescapable consequence of the interaction between system and environment degrees of freedom, which, among other things, is responsible for the quantum-to-classical transition of primordial perturbations. The effects of entanglement are computed using open QFT techniques, which allow to account for the non-unitary evolution of the system via the master equation for the reduced density matrix. We consider the process to be mediated by the leading gravitational nonlinearities in the Einstein-Hilbert action, which allows us to find a universal lower bound of the effects of entanglement in single-field slow-roll inflation. This reveals new predictions for inflation and highlights the underdeveloped link between quantum information theory and cosmology.

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