Видео 19
Просмотров 1 476

Marta Maria Marchese - Coherently Averaged Optmechanical Sensing

53:57

Guilherme Franzmann - Are quantum subsystems invariant?

1:11:55

Chris Mitsch - Some Lessons from Haag's Theorem

1:06:31

Fil Simovic - Understanding emergent geometry through symmetry breaking

1:12:59

Daniel Terno - Spin, localisation and uncertainty relations

58:32

Julian De Vuyst - Gravitational entropy is observer-dependent

58:33

Thiago Guerreiro - Nonclassical gravitational waves and the quantum nature of gravity

*Abstract:* Einstein's theory of gravity admits a low energy effective quantum field description from which predictions beyond classical general relativity can be made. As gravitational wave detectors improve, we may ask whether nonclassical features of such theory can be experimentally verified? In this talk, I will discuss three aspects of this question: First, what kinds of signals would nonclassical gravitational waves impart on a detector? Next, what would we need to measure in order to certify the quantum nature of gravity? And finally, do nonclassical gravitational wave states get produced in Nature, and if yes, what are the sources?
*Talk page:* researchseminars.org/talk/3cqfs/32/
_...

Видео

Marta Maria Marchese - Coherently Averaged Optmechanical Sensing

53:57

Marta Maria Marchese - Coherently Averaged Optmechanical Sensing

Просмотров 20Месяц назад

*Abstract:* Coherent averaging schemes have been introduced as a method to achieve the Heisenberg limit in parameter estimation. Typically, these schemes involve multiple probes in a product state interacting with a quantum bus, with parameter estimation performed via measurements on the bus. We propose a novel coherent averaging scheme for force sensing using an array of optomechanical detecto...

Guilherme Franzmann - Are quantum subsystems invariant?

1:11:55

Guilherme Franzmann - Are quantum subsystems invariant?

Просмотров 112Месяц назад

*Abstract:* What is a physical subsystem? How classical physical subsystems localized in spacetime (causally independent) are identified from quantum ones? Traditionally, classical systems have been uniquely identified with quantum systems, typically represented as factors in Hilbert space for finite-dimensional systems or associated with a local (microcausality) algebra of operators in QFT. Bo...

Chris Mitsch - Some Lessons from Haag's Theorem

1:06:31

Chris Mitsch - Some Lessons from Haag's Theorem

Просмотров 772 месяца назад

*Abstract:* Haag’s theorem is a classic no-go theorem: it rigorously demonstrates that there is a conflict between the interaction picture and other basic, intuitive-seeming assumptions in QFT. The precise significance of the theorem continues to be debated, however. I will focus on two big-picture questions in this talk. First, why are there multiple, distinct responses to Haag's theorem? Here...

Fil Simovic - Understanding emergent geometry through symmetry breaking

1:12:59

Fil Simovic - Understanding emergent geometry through symmetry breaking

Просмотров 873 месяца назад

*Abstract:* Quantum field theory correlators allow for the reconstruction of spacetime geometry from information-theoretic quantities, leading to a viewpoint in which the fundamental role of spacetime is subsumed by different, potentially abstract, measures of correlation. Recent work has demonstrated the emergence of higher-dimensional anti-de Sitter geometries from this perspective, with an e...

Daniel Terno - Spin, localisation and uncertainty relations

58:32

Daniel Terno - Spin, localisation and uncertainty relations

Просмотров 194 месяца назад

*Abstract:* Defining a relativistic position operator poses significant challenges, even without considering particle creation and annihilation. The solution involves using positive operator-valued measures (POVMs), though they are not unique. This non-uniqueness also affects the relativistic generalization of non-relativistic spin. In this talk, I will describe POVMs for scalar particles, phot...

Julian De Vuyst - Gravitational entropy is observer-dependent

58:33

Julian De Vuyst - Gravitational entropy is observer-dependent

Просмотров 1915 месяцев назад

*Abstract:* In quantum gravity, it has been argued that a proper accounting of the role played by an observer promotes the von Neumann algebra of observables in a given spacetime subregion from Type III to Type II. While this allows for a mathematically precise definition of its entropy, we show that this procedure depends on which observer is employed. We make this precise by considering a set...

Ioannis Soranidis - Kinematic, energetic, and thermodynamic properties of regular black holes

1:02:08

Ioannis Soranidis - Kinematic, energetic, and thermodynamic properties of regular black holes

Просмотров 1105 месяцев назад

*Abstract:* Regular black holes have become a popular alternative to the singular mathematical black holes predicted by general relativity as they circumvent mathematical pathologies associated with the singularity while preserving crucial black hole features such as the trapping of light. Here, we will analyze how to generate these geometries and study their thermodynamic properties within the...

Anne-Catherine de la Hamette - Identification is pointless

1:14:51

Anne-Catherine de la Hamette - Identification is pointless

Просмотров 1646 месяцев назад

*Abstract:* A first step towards scenarios at the interface of quantum theory and gravity is to consider a quantum superposition of semiclassical spacetimes, such as the one, arguably, sourced by a gravitating object in superposition. But what does it mean that a gravitational source is in a superposition of “different” locations? How can one compare points across the different manifolds? Due t...

Erickson Tjoa - The Unruh-DeWitt model and its joint interacting Hilbert space

1:18:19

Erickson Tjoa - The Unruh-DeWitt model and its joint interacting Hilbert space

Просмотров 366 месяцев назад

*Abstract:* In this work we make the connection between the Unruh-DeWitt particle detector model applied to quantum field theory in curved spacetimes and the rigorous construction of the spin-boson model. With some modifications, we show that existing results about the existence of a spin-boson ground state can be adapted to the Unruh-DeWitt model. In the physically relevant setting involving m...

Aristotelis Panagiotopoulos - Incompleteness Theorems for Observables in General Relativity

1:08:16

Aristotelis Panagiotopoulos - Incompleteness Theorems for Observables in General Relativity

Просмотров 1037 месяцев назад

*Abstract:* One of the biggest open problems in mathematical physics has been the problem of formulating a complete and consistent theory of quantum gravity. Some of the core technical and epistemological difficulties come from the fact that General Relativity (GR) is, fundamentally, a geometric theory and, as such, it oughts to be `generally covariant', i.e. invariant under change of coordinat...

Flaminia Giacomini - Quantum effects in gravity beyond the Newton potential

54:36

Flaminia Giacomini - Quantum effects in gravity beyond the Newton potential

Просмотров 938 месяцев назад

*Abstract:* Understanding the fundamental nature of gravity at the interface with quantum theory is a major open question in theoretical physics. Recently, the study of gravitating quantum systems, for instance a massive quantum system prepared in a quantum superposition of positions and sourcing a gravitational field, has attracted a lot of attention: experiments are working towards realising ...

Navdeep Arya - Unruh effect inside a cylindrical cavity

1:19:25

Navdeep Arya - Unruh effect inside a cylindrical cavity

Просмотров 528 месяцев назад

*Abstract:* The Unruh effect states that the transition rates of a uniformly accelerated detector in the inertial vacuum have a thermal character at a temperature proportional to the detector's acceleration. Numerous proposals studying different properties of the accelerated detector under varied settings still await fruition as the signal of interest is generally very weak. We will discuss the...

Robert B. Mann - The Holographic Chemistry of Black Holes

1:27:31

Robert B. Mann - The Holographic Chemistry of Black Holes

Просмотров 758 месяцев назад

*Abstract:* Black Holes are amongst the strangest objects in the universe. They form from the collapse of matter into an object whose gravitational pull is so strong, nothing can escape from them. Yet a black hole also radiates heat like a blackbody, with a temperature equal to its surface gravity, an entropy equal to its area, and an energy equal to its mass. Over the past 15 years we have com...

Nicolas C. Menicucci - Tachyonic media in sonic relativity

1:05:02

Nicolas C. Menicucci - Tachyonic media in sonic relativity

Просмотров 6710 месяцев назад

*Abstract:* In sonic models of special relativity, the fact that the sonic medium violates (ordinary) Lorentz symmetry is apparent to observers external to the sonic medium but not to a class of observers existing within the medium itself. We show that the situation is symmetric: internal observers will judge physics in the external laboratory to violate their own sonic Lorentz symmetries. We t...