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Visar resultat 1 - 5 av 6 uppsatser som matchar ovanstående sökkriterier.

  1. 1. Gravitational Collapse of a Massless Scalar Field in a Theory of Minimally Modified Gravity

    Master-uppsats, KTH/Fysik

    Författare :Atabak Fathe Jalali; [2024]
    Nyckelord :Theoretical physics; astrophysics; modified gravity; minimally modified gravity; gravitational collapse; VCDM; scalar collapse; apparent horizon; numerical relativity; Teoretisk fysik; astrofysik; modifierad gravitation; minimalt modifierad gravitation; gravitationskollaps; VCDM; skalär kollaps; uppenbar horisont; numerisk relativitet;

    Sammanfattning : This thesis explores the spherically symmetric gravitational collapse of a massless scalar field in a minimally modified gravity theory denoted VCDM (V replaces $\Lambda$ in the $\Lambda$CDM abbreviation), a class of theories propagating the same degrees of freedom as general relativity at the expense of broken 4D diffeomorphism invariance. Numerical evolution of the equations of motion reveals that for small initial scalar profile amplitudes, no black hole forms from the collapse. LÄS MER

  3. 2. Planes of satellite galaxies

    Kandidat-uppsats, Lunds universitet/Astronomi - Genomgår omorganisation

    Författare :Jessica Laura Erika Kocher; [2022]
    Nyckelord :Physics and Astronomy;

    Sammanfattning : The Planes of Satellites Problem is an open question within the field of galaxy formation. It is based on the observations that the Milky Way's satellites, as well as those around the Andromeda (M31) galaxy, align in planes. LÄS MER

  4. 3. Markov Chain Monte Carlo (MCMC) and Bayesian Inference for Gravitational Waves

    Kandidat-uppsats, Lunds universitet/Astronomi - Genomgår omorganisation

    Författare :Christine Andersson; [2021]
    Nyckelord :Gravitational Waves; LISA; LISA mission; Bayesian Inference; Markov Chain Monte Carlo; MCMC; Bayes’ Theorem; stochastic sampling; Metropolis Hastings; histograms; Physics and Astronomy;

    Sammanfattning : The Laser Interferometer Space Antenna (LISA) is a space borne gravitational wave detec- tor set to launch in 2034, with the objective of detecting and studying the Gravitational Waves (GWs) of our universe. So far, ground-based detectors such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) have been successful in detecting GWs, but the limitations of ground based detectors is what makes LISA so special. LÄS MER

  5. 4. Effect of chameleons on the mass of a galaxy cluster

    Master-uppsats, Uppsala universitet/Teoretisk astrofysik

    Författare :Isabel Roca Vich; [2019]
    Nyckelord :Chameleons; modified gravity; galaxy cluster;

    Sammanfattning : Chameleons are scalar fields coming from modied gravity theories and can be possible explanations for Dark Energy. They cause a fifth force and have a screening mechanism which allows this force to avoid solar system constraints. In this thesis, astrophysical consequences of the potential presence of the chameleon field will be studied. LÄS MER

  7. 5. On the consistency of multigravity theories

    Master-uppsats, Stockholms universitet/Fysikum

    Författare :Marcus Högås; [2016]
    Nyckelord :Gravity; Modified theories for gravity; Bimetric gravity; Multimetric gravity; Bigravity; Multigravity; Consistency; Deser-van Nieuwenhuizen condition; Symmetric vielbein condition; Symmetrization condition;

    Sammanfattning : In this thesis a set of recently proposed multigravity theories is analysed. In the special case of bimetric gravity, the theory has been conclusively shown to be ghost-free. On the other hand, for multigravity theories in general, the ghost-issue has not been settled conclusively. LÄS MER