Emergent Gravitation

master's thesis

• Title (croatian): Izranjajuća gravitacija
• Author: Kaja Krhač
• Mentor: Ivica Smolić (mentor)
• Committee member: Ivica Smolić (predsjednik povjerenstva)
• Committee member: Maro Cvitan (član povjerenstva)
• Committee member: Matko Milin (član povjerenstva)
• Committee member: Krešimir Kumerički (član povjerenstva)
• Committee member: Mihael Makek (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2021-02-22, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

The general theory of relativity describes gravitation as a curvature of spacetime, smooth manifold with Lorentzian metric. A different light was shed on the theory with the discovery that black holes behave as thermodynamic objects, satisfying laws analogous to the one of thermodynamics and radiating with a thermal spectrum, confirming that gravitation, thermodynamics, and quantum theory are intimately related. Taking this connection seriously led to attempts, united under the name “Emergent Gravitation", to describe gravitation as an emergent phenomenon, a result of collective motion of some yet unknown microscopic degrees of freedom. In this work, we give an overview of various models of Emergent Gravitation, as well as the constraints such models should satisfy to reproduce General Relativity at a larger scale. We consider different lines of thinking in the Emergent Gravitation approach by studying Causal Set Theory as a representative of Emergent Gravitation models where spacetime is considered as a derived notion, resulting from coarse-graining of a discrete set of points with causal relations between them, Weinberg-Witten theorem as a constraint on an idea that graviton, a mediator of gravitational interaction is emergent, and the role of thermodynamics in General Relativity in the scope of black holes and their horizons, but also horizons in general.

Abstract (croatian)

Opća teorija relativnosti opisuje gravitaciju kao zakrivljenost prostorvremena, glatke mnogostrukosti s Lorentzovom metrikom. Otkriće da crne rupe zadovoljavaju zakone analogne zakonima termodinamike te da zrače termalnim spektrom bacilo je drugačije svjetlo na opću teoriju relativnosti i utvrdilo vezu između opće relativnosti, termodinamike i kvantne teorije. Ozbiljno shvaćanje te veze dovelo je do pokušaja da se gravitacija opiše kao izranjajući fenomen, rezultat kolektivnog gibanja nekih trenutno nepoznatih mikroskopskih stupnjeva slobode, a paradigma je dobila ime “izranjajući gravitacija". U ovom radu dan je pregled različitih modela izranjajuće gravitacije, kao i ograničenja koje takva teorija mora zadovoljavati kako bi uspješno reproducirala opću teoriju relativnosti na makroskopskoj skali. U radu razmatramo različite pristupe paradigmi izranjajuće gravitacije na primjeru kauzalne teorije skupova gdje se prostorvrijeme uzima kao izveden koncept koje je rezultat uprosječivanja diskretnog skupa točaka između kojih postoje kauzalne relacije, Weinberg-Wittenovog teorema koji postavlja ograničenja na ideju da je graviton, medijator gravitacijske interakcije, "izranjajuć" i ulogu termodinamike u općoj teoriji relativnosti u sklopu crnih rupa, ali i horizonata općenito.

• Keywords: general relativity; emergence; causal set theory; Weinberg-Witten theorem; black hole thermodynamics; spacetime thermodynamics
• Keywords (croatian): opća teorija relativnosti; kauzalna teorija skupova; Weinberg-Wittenov teorem; termodinamika crnih rupa; termodinamika prostorvremena
• Language: english
• URN:NBN: urn:nbn:hr:217:166781
• Study programme: Title: Physics; specializations in: Research; Course: Research; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra fizike (magistar/magistra fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2021-04-28 12:02:59