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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Information propagation and entanglement generation between two Unruh-DeWitt detectors

Cliche, Mathieu January 2010 (has links)
The setup in which two quantum systems, Alice and Bob, communicate using bosonic field quanta can be viewed as a prototype for wireless quantum communication. In this thesis we focus on the most basic case, where Alice and Bob are modeled as Unruh-DeWitt detectors, i.e., as two-level quantum systems that interact locally through a scalar quantum field. Our aim is to study how information propagation and entanglement generation between the two detectors are impacted by both relativity and by the unavoidable noise that is due to the quantum fluctuations of the field. We start by studying information propagation between the two detectors. Concretely, we construct and study the information-theoretic quantum channel, ξ, i.e., the completely positive trace preserving map between the input density matrix ϱ, in which Alice prepares her detector for the emission, and the output density matrix ϱ '=ξ(ϱ) of Bob's detector at a later time. We confirm that the classical as well as the quantum channel capacity are strictly zero to all orders in perturbation theory for spacelike separations. We then study entanglement generation between the two detectors. Specifically, we discuss how two Unruh-DeWitt detectors can extract entanglement from the vacuum. We show that the detectors can naturally and instantaneously become entangled through a Casimir-Polder effect. We then analyze the impact of various additions to this setup, such as the presence of a weak gravitational field, the presence of boundary conditions in the field, the presence of a weak classical potential, etc.
12

Kanonické kvantování midisuperspace modelů / Canonical quantization of midisuperspace models

Černý, Jiří January 2018 (has links)
In this work we will try to quantize midisuperspace model of spherically sym- metric spacetime with massless scalar field. On this type of spacetimes we apply Dirac method of canonical quantization, leading to Wheeler-DeWitt equations. We will attempt to solve those equation generally for aforementioned type of spa- cetimes. Our initial midisuperspace model is Roberts dynamical spacetime. As we will see later, Roberts metric behaves badly in the asymptotic region. Due to this problematic behaviour of Roberts spacetime at the boundary, we will choose to quantize its static version, the special Janis-Newman-Winicour spacetime. This midisuperspace model is static, asymptotically flat spacetime with scalar field and it contains a naked time-like singularity. For special Janis-Newman-Winicour spacetime we will then solve Wheeler-DeWitt equations.
13

The Bose/Fermi oscillators in a new supersymmetric representation

Ihl, Matthias, 1977- 25 October 2011 (has links)
This work deals with the application of supermathematics to supersymmetrical problems arising in physics. Some recent developments are presented in detail. A reduction scheme for general supermanifolds to vector bundles is presented, which significantly simplifies their mathematical treatment in a physical context. Moreover, some applications of this new approach are worked out, such as the Fermi oscillator. / text
14

Jean-Jacques Rousseau et la science politique de son temps.

Derathé, Robert. January 1950 (has links)
Thèse. Lettres. Paris. 1950.
15

Quantum gravity in two- and three-dimensional dS spaces

Chernichenko, Alexsey January 2024 (has links)
This thesis is a study of certain aspects of quantum gravity in two- and three-dimensional de Sitter spaces. The model used in dS2 is the Jackiw- Tetitelboim gravity which involves a scalar coupling. At low-energy limit this model becomes Schwarzian theory for which one can compute one-loop partition function. Along the way, the model is recasted into the first order formalism which helps to find an appropriate measure for the partition function. The layout for quantum gravity in dS3 is practically the same and many results appear to be quite similar. Although, there are as many dissimilarities. Ultimately, the goal is different, namely to determine one-loop correction to the central charge of the theory dual to dS3 . Additionally, a putative genus expansion for Jackiw-Teitelboim gravity is investigated along with some concrete computations being done. / Detta examensarbete ̈ar en studie av vissa aspekter av kvantgravita-tion i två och tredimensionella de Sitter-rummen. Den behandlar Jackiw-Teitelboim gravitation i dS2 , en model med en skalär koppling. Vid lågenergigränns blir modellen till Schwarzian teorin som används för att beräkna första ordningskorrektionen till partitionsfunktion. På vägen dit skrivs om modelen till första ordningens formalism som sedan hjälper att hitta ett lämpligt mått för partitionsfunktionen. Plannen för dS3 ser ut i princip likadant och en stor del av resultater är liknande. Emellertid finns det lika många olikheter. I slut änden, målet är annorludna, nämligen att beräkna första ordningens korrektion till centrala laddningen av teorin som dual till dS3 . Dessutom, en förmodad genus expansion för Jackiw-Teitelboim gravitation är undersökt och vissa konkreta beräkningar är gjorda.
16

THE BRONX COCKED BACK AND SMOKING MULTIFARIOUS PROSE PERFORMANCE

Avila, Alex 01 June 2016 (has links)
The Bronx Cocked Back And Smoking is a collection of multifarious prose performances recounting the historical, personal, social, political and cultural constructs of a city birthed by violence. This body of work is accompanied by video, audio, photography, and theatre performance texts. St. Mary’s Housing project, in the Bronx, is the foundation where most of this literary work takes place. The modern day Griot (storyteller) is a Poet, guiding his audience through the social inequalities and disparities that plague St. Mary’s community. The Poet shares personal traumatic insights while simultaneously utilizing writing as a form of survival to the conditions of the Bronx. This multi-platform performance highlights the metaphorical and physical concerns with the cycle of violence. This question is answered through the Poet’s choice by selecting the pen over the gun.

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