Measurement of the power spectrum from a N-body cosmological simulation andapplication to the search for dark matter

Vodeb, Veronika (author), Gomboc, Andreja (mentor), Zaharijaš, Gabrijela (comentor)

The nature of dark matter particle is one of the biggest puzzles in physics today. Gamma-rays (as measured by e.g. Fermi LAT NASA satellite) are particularly powerful ways to test one of the most popular particle physics proposal, WIMPs. However, to test particle physics properties via gamma-rays, dark matter clustering along a line of sight needs to be known. In this work we use the latest knowledge from N-body simulations of DM clustering to update the predictions of gamma-ray signal from dark matter annihilation in all dark matter halos at all redshifts, the so-called cosmological dark matter signal. This works makes part of the ongoing work within the Fermi LAT collaboration, which aims to update the search for the dark matter cosmological signal, previously performed in 2015. In the introductory chapters we review the basics of the $\Lambda$CDM standard model of cosmology, the physics of DM clustering and its potential gamma-ray signals. We then focus on the calculation of the DM clustering contribution to the gamma ray signal, the so called flux multiplier $\zeta$. We describe the two different approaches to calculating its value - the Power Spectrum approach, and the Halo Model approach. We discuss the technical aspects of both approaches and describe the quantities used in each of them with the aim to improve the existing results by using the state-of-art value for different functions, which became available since the last work in 2015. In the context of the halo model approach we prepare the machinery to re-evaluate theoretical prediction of DM signal that depends on DM clustering and derive the first results. In the context of the power spectrum approach, we measure the power spectrum of the full-box Lomonosov simulation and compare our results with the power spectrum measured of the Millennium and Millennium II simulations.

• Language: English
• Keywords: kozmologija, temna snov, spekter moči, halo model
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FMF - Faculty of Mathematics and Physics
• Year: 2019
• PID: 20.500.12556/RUL-110354
• COBISS.SI-ID: 3370084
• Publication date in RUL: 14.09.2019

Secondary language

• Language: Slovenian
• Title: Meritev spektra moči iz večdelčne kozmološke simulacije in uporaba pri iskanju temne snovi

Abstract

Narava delcev temne snovi je dandanes ena največjih ugank v fiziki. Detekcija sevanja gama (izmerjeno na primer s satelitom Fermi LAT NASA) predstavlja še posebej močan način za preizkušanje enega najbolj priljubljenih kandidatov fizike delcev za opis temne snovi, WIMP. Ob tem je potrebno za preizkušanje fizikalnih lastnosti omenjenih delcev s sevanjem gama poznati zgoščenost temne snovi vzdolž smeri gledanja. V tem delu uporabljamo najnovejše znanje pridobljeno s pomočjo večdelčnih kozmoloških simulacij temne snovi, da z njim posodobimo napovedi signala sevanja gama, ki prihaja iz anihilacije temne snovi v vseh halojih temne snovi pri vseh rdečih premikih, tako imenovani - kozmološki signal temne snovi. To delo je del trenutnih prizadevanj Fermi LAT kolaboracije za posodobitev iskanja kozmološkega signala temne snovi, ki je bilo nazadnje izvedeno leta 2015. V uvodnih poglavjih pregledamo osnove $\Lambda$CDM standardnega modela kozmologije, teoretični opis zgoščevanja temne snovi in možnosti temne snovi za sevanje gama svetlobe. V nadaljevanju se osredotočimo na izračun prispevka temne snovi k signalu sevanja gama, tako imenovani množitelj toka $\zeta$. Opišemo dva različna pristopa za izračun njegove vrednosti - pristop spektra moči in pristop halo modela. Razpravljamo o tehničnih vidikih obeh pristopov in opišemo količine, ki so uporabljene v posameznem pristopu z namenom izboljšanja obstoječih rezultatov z uporabo posodobljenih funkcij, ki so postale na voljo od zadnje objave leta 2015. V okviru pristopa s halo modelom pripravimo enačbe za ponovno oceno teoretično napovedanega signala temne snovi, ki je odvisen od zgoščevanja temne snovi in njene porazdelitve po Vesolju, ter pridobimo prve rezultate. V okviru pristopa spektra moči izmerimo spekter moči iz polne simulacije Lomonosov in primerjamo naše rezultate s spektrom moči izmerjenim z uporabo simulacij Millennium in Millennium II.

• Keywords: cosmology, dark matter, power spectrum, halo model