Browsing NTNU Open by Author "Andersen, Jens Oluf"
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A SoftLimit Theorem for the OnShell Scattering Amplitudes Describing Processes Involving Massive NambuGoldstone Bosons
Jakobsen, Martin Fonnum (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
Andersen, Jens Oluf; Naylor, William; Tranberg, Anders (Journal article; Peer reviewed, 2014)We use the Polyakov loop coupled quarkmeson 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
Andersen, Jens Oluf; Kneschke, Patrick (Journal article; Peer reviewed, 2018)The quarkmeson model is often used as a lowenergy 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
Andersen, Jens Oluf; adhikari, prabal (Journal article; Peer reviewed, 2017)In this paper, we study the possibility of an inhomogeneous quark condensate in the (1 þ 1)dimensional NambuJonaLasinio model in the largeNc limit at finite temperature T and quark chemical potential μ using dimensional ... 
Chiral perturbation theory in a magnetic background  finitetemperature effects
Andersen, Jens Oluf (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
Andreassen, Vegar (Master thesis, 2017)In this thesis we study the massradius and pressureradius relations of white dwarfs and neutron stars. We derive the pressure and energy density in a noninteracting Fermi gas at $T=0$, and construct several different ... 
Condensates and pressure of twoflavor chiral perturbation theory at nonzero isospin and temperature
Andersen, Jens Oluf; Mojahed, Martin Aria; Adhikari, Prabal (Peer reviewed; Journal article, 2021)We consider twoflavor 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
Andersen, Jens Oluf; adhikari, prabal (Journal article; Peer reviewed, 2017)In many models in condensed matter and highenergy 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 TwoHiggs Doublet Model with a softly broken Z2 symmetry at oneloop
Helset, Andreas (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 manybody systems
Andersen, Jens Oluf; Brauner, Tomas; Hofmann, CP; Vuorinen, Aleksi (Journal article; Peer reviewed, 2014)The lowenergy and lowmomentum dynamics of systems with a spontaneously broken continuous symmetry is dominated by the ensuing NambuGoldstone bosons. It can be conveniently encoded in a modelindependent effective field ... 
Effective Polyakov Loop Modeling of QCD  A Field Theoretical Study of the Phase Diagram of Quark Matter
Folkestad, Åsmund Schiager (Master thesis, 2018)In this thesis we study the phase diagram of twoflavor 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 Lorentzinvarians på NambuGoldstone bosoner
Krohg, Fredrik Nicolai (Master thesis, 2015)I denne avhandlingen diskuterer vi symmetrier av feltteorier både med og uten Lorentzinvarians. Vi konstruerer en feltteori fri for interaksjoner som er invariant under den Euklidske gruppen E(2), har tilhørende EulerLagrange ... 
Field Theory at finite Temperature and Density: Applications to Quark Stars
Strumke, Inga (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 TolmanOppenheimerVolkoff (TOV)equations to ... 
Goldstone bosons at finite density  Study of spontaneous symmetry breaking in O(N)symmetric theories at finite chemical potential
Sanchez Garcia, Alfredo Ignacio (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 quarkmeson model
Adhikari, Prabal; Andersen, Jens Oluf; Kneschke, Patrick (Journal article; Peer reviewed, 2017)The twoflavor quarkmeson model is used as a lowenergy 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
Hindar, Erlend (Master thesis, 2019)I denne oppgaven utleder vi Einsteins feltligninger fra EinsteinHilbert actionen ved å bruke variasjonsprinsipper. Videre ser vi på svakfelt grensen av disse ligningene ved å benytte en lineær approksimasjon. Gjennom en ... 
Inverse magnetic catalysis and regularization in the quarkmeson model
Andersen, Jens Oluf; Naylor, William; Tranberg, Anders (Journal article; Peer reviewed, 2015)Motivated by recent work on inverse magnetic catalysis at finite temperature, we study the quarkmeson model using both dimensional regularization and a sharp cutoff. We calculate the critical temperature for the chiral ... 
Linearized general relativity and its quantization
Pedersen, AlfHåkon (Master thesis, 2017)We begin by deriving the Einstein equation from the EinsteinHilbert 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 meanfield approximation
Sivertsen, Lars (Master thesis, 2018)Various models for the equation of state (EoS) for a neutron star have been considered using the relativistic meanfield approximation. Firstly, we derive Einstein's field equations and apply them to a spherically symmetric ... 
Neutron Stars  Study of the MassRadius Relation and MeanField Approaches to the Equation of State
Pogliano, Francesco (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 ...