Now showing items 1-20 of 39

• #### A Soft-Limit Theorem for the On-Shell Scattering Amplitudes Describing Processes Involving Massive Nambu-Goldstone Bosons ﻿

(Master thesis, 2017)
In this thesis we consider systems where both Lorentz invariance and a continuous symmetry group G is explicitly broken by coupling a chemical potential µ to one of the generators Q of G. In such systems it is well known ...
• #### Chiral and deconfinement transitions in a magnetic background using the functional renormalization group with the Polyakov loop ﻿

(Journal article; Peer reviewed, 2014)
We use the Polyakov loop coupled quark-meson model to approximate low energy QCD and present results for the chiral and deconfinement transitions in the presence of a constant magnetic background B at finite temperature T ...
• #### Chiral density wave versus pion condensation at finite density and zero temperature ﻿

(Journal article; Peer reviewed, 2018)
The quark-meson model is often used as a low-energy effective model for QCD to study the chiral transition at finite temperature T, baryon chemical potential μB, and isospin chemical potential μI. We determine the parameters ...
• #### Chiral density wave versus pion condensation in the (1+1)-dimensional NJL model ﻿

(Journal article; Peer reviewed, 2017)
In this paper, we study the possibility of an inhomogeneous quark condensate in the (1 þ 1)-dimensional Nambu-Jona-Lasinio model in the large-Nc limit at finite temperature T and quark chemical potential μ using dimensional ...
• #### Chiral perturbation theory in a magnetic background - finite-temperature effects ﻿

(Journal article; Peer reviewed, 2012)
We consider chiral perturbation theory for SU(2) at finite temperature T in a constant magnetic background B. We compute the thermal mass of the pions and the pion decay constant to leading order in chiral perturbation ...
• #### Compact Stars ﻿

(Master thesis, 2017)
In this thesis we study the mass-radius and pressure-radius relations of white dwarfs and neutron stars. We derive the pressure and energy density in a non-interacting Fermi gas at $T=0$, and construct several different ...
• #### Condensates and pressure of two-flavor chiral perturbation theory at nonzero isospin and temperature ﻿

(Peer reviewed; Journal article, 2021)
We consider two-flavor chiral perturbation theory (χPT) at finite isospin chemical potential μI and finite temperature T . We calculate the effective potential and the quark and pion condensates as functions of T and μI ...
• #### Consistent regularization and renormalization in models with inhomogeneous phases ﻿

(Journal article; Peer reviewed, 2017)
In many models in condensed matter and high-energy physics, one finds inhomogeneous phases at high density and low temperature. These phases are characterized by a spatially dependent condensate or order parameter. A proper ...
• #### Dimensional reduction of the Two-Higgs Doublet Model with a softly broken Z2 symmetry at one-loop ﻿

(Master thesis, 2017)
In the collaboration between NTNU, the University of Stavanger, and the University of Helsinki we pursue a satisfactory answer to the problem of baryogenesis, i.e. the origin of the asymmetry in the amount of baryons and ...
• #### Effective Lagrangians for quantum many-body systems ﻿

(Journal article; Peer reviewed, 2014)
The low-energy and low-momentum dynamics of systems with a spontaneously broken continuous symmetry is dominated by the ensuing Nambu-Goldstone bosons. It can be conveniently encoded in a model-independent effective field ...
• #### Effective Polyakov Loop Modeling of QCD - A Field Theoretical Study of the Phase Diagram of Quark Matter ﻿

(Master thesis, 2018)
In this thesis we study the phase diagram of two-flavor quantum chromodynamics with effective models. We investigate the phase diagram in the baryon chemical potential temperature and magnetic field temperature planes. As ...
• #### Effekter av manglende Lorentz-invarians på Nambu-Goldstone bosoner ﻿

(Master thesis, 2015)
I denne avhandlingen diskuterer vi symmetrier av feltteorier både med og uten Lorentz-invarians. Vi konstruerer en feltteori fri for interaksjoner som er invariant under den Euklidske gruppen E(2), har tilhørende Euler-Lagrange ...
• #### Field Theory at finite Temperature and Density: Applications to Quark Stars ﻿

(Master thesis, 2012)
Abstract:In this thesis we will consider different thermal field theories, and derive an equation of state for deconfined matter.This equation of state will be used in the Tolman-Oppenheimer-Volkoff (TOV)-equations to ...
• #### Goldstone bosons at finite density - Study of spontaneous symmetry breaking in O(N)-symmetric theories at finite chemical potential ﻿

(Master thesis, 2017)
Goldstone s theorem states that, in presence of Lorentz invariance, the number of massless modes that appear after spontaneous symmetry breaking coincides with the number of broken generators. These modes are called Goldstone ...
• #### Inhomogeneous chiral condensate in the quark-meson model ﻿

(Journal article; Peer reviewed, 2017)
The two-flavor quark-meson model is used as a low-energy effective model for QCD to study inhomogeneous chiral condensates at finite baryon chemical potential μB . The parameters of the model are determined by matching the ...
• #### Introduksjon til gravitasjonsbølger ﻿

(Master thesis, 2019)
I denne oppgaven utleder vi Einsteins feltligninger fra Einstein-Hilbert actionen ved å bruke variasjonsprinsipper. Videre ser vi på svak-felt grensen av disse ligningene ved å benytte en lineær approksimasjon. Gjennom en ...
• #### Inverse magnetic catalysis and regularization in the quark-meson model ﻿

(Journal article; Peer reviewed, 2015)
Motivated by recent work on inverse magnetic catalysis at finite temperature, we study the quark-meson model using both dimensional regularization and a sharp cutoff. We calculate the critical temperature for the chiral ...
• #### Linearized general relativity and its quantization ﻿

(Master thesis, 2017)
We begin by deriving the Einstein equation from the Einstein-Hilbert action integral using variational methods; Variation with respect to the metric and the Palatini variation. The vacuum solution (Schwarzschild solution) ...
• #### Neutron stars - Investigating candidates for the equation of state in the relativistic mean-field approximation ﻿

(Master thesis, 2018)
Various models for the equation of state (EoS) for a neutron star have been considered using the relativistic mean-field approximation. Firstly, we derive Einstein's field equations and apply them to a spherically symmetric ...
• #### Neutron Stars - Study of the Mass-Radius Relation and Mean-Field Approaches to the Equation of State ﻿

(Master thesis, 2017)
The structure and the relation between the total mass, the radius and the central energy density of a neutron star may be found by numerically solving a set of three coupled differential equations. One of these equations ...