Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 14 of 14 for “"Cosmic strings"”.
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Cosmic string cusps and their application to fast radio bursts
… characteristics of two theoretical aspects of cosmic strings. The first is relativistic modification of cusps. Nambu-Goto strings generically develop cusps, regions of the string which emit coherent electromagnetic radiation when they decay. We point out that consideration of relativistic …
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Cosmic String Radiation with Adaptive Mesh Refinement
Cosmic strings are a fundamental feature of many physically-motivated field theories which inevitably form in the early Universe, as a result of a symmetry breaking phase transition. An important example is the Peccei-Quinn mechanism, from which strings emerge as a potential source of dark matter …
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The power spectrum and bispectrum of inflation and cosmic defects
… has come from studying the power spectrum of the cosmic microwave background (CMB). The latest results from the Planck satellite confirmed that the inflationary paradigm with the $\Lambda$CDM six-parameter model provides a very good description of the observed structures in the Universe. Even so, …
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Gravitational waves from a string cusp in Einstein-aether theory
… in the gravitational waves emitted by cosmic strings. Aspects of cosmic strings are reviewed, in particular how focused bursts of gravitational radiation are emitted when a cusp forms on the string. The same phenomenon is then studied in an effective field theory with Lorentz violation …
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Fractality and topology of optical singularities
… of vortices in random discrete lattice models of cosmic strings, implying that the statistics of singularities in random optical fields exhibit universal behavior. It is also established that a random superposition of plane-waves, such as optical speckle, form singularities which not only map out …
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ΠΑΡΑΓΩΓΗ ΝΕΩΝ ΑΚΡΙΒΩΝ ΛΥΣΕΩΝ ΤΩΝ ΕΞΙΣΩΣΕΩΝ ΤΟΥ EINSTEIN ΜΕ ΤΗ ΜΕΘΟΔΟ ΤΗΣ ΑΝΤΙΣΤΡΟΦΗΣ ΣΚΕΔΑΣΗΣ ΤΩΝ BELINSKY-ZAKHAROV
… AND ARE PHYSICALLY INTERPRETED AS MODELS OF COSMIC STRINGS IN THE ENVIRONMENT OF CYLINDRICAL WAVES, AS ROTATING BOUNDER SOURCES AS COSMOLOGICAL SOLUTIONS AND AS MODELS FOR ONE INTERACTION REGIONS RESULTING AFTER THE COLLISION OF PLANE GRAVITATIONAL WAVES.
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Fundamental physics from observations of the early universe
… future data on the existence and properties of cosmic strings, a prediction of GUT and superstring theories, and the variation of fundamental constants.
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Microcanonical simulations in classical and quantum field theory
… of the evolution of a network of global cosmic strings in an expanding Robertson-Walker universe is carried out. The system is quenched through an order-disorder phase transition and the nature of the string distribution is examined. While the string distribution observed at the phase …
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Probing the First Stars with the 21-cm Signal: Theory, Methods, and Forecasts
… feedback. Chapter 4 investigates how cosmic rays emitted via the supernovae of the first stars can heat the intergalactic medium and imprint distinctive signatures on the 21-cm signal. And finally, Chapter 5 shows that variations in X-ray binary emissivity and abundances enhance the …
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Large-scale structure of the early universe
… constant, fo = 0.2 and models involving cosmic strings. • the discovery of a quasar with ultrastrong ultraviolet Fe II emission The unusual emission features seen in this quasar are explained by Lya fluorescence contributing significantly to the formation of Fe II emission.
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Cosmology with CMB and Large Scale Structure
… new statistical and numerical tools to study the Cosmic Microwave Background (CMB) radiation and Large Scale Structure(LSS), in order to test different models of the Universe. This is the main aim of this thesis. The standard inflationary $\Lambda$-dominated Cold Dark Matter ($\Lambda$CDM) model …
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Void boundaries in the southern sky : aspects of large scale structure in southern galaxy catalogues
… In addition, voids are able to "hide" in the cosmic microwave background. Thus even though the largest structures found in redshift surveys (superclusters) tend to be as large as the extents of the surveys, it is conceivable that one way, of fitting a homogeneous and isotropic Friedmann model …
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Enhancing the detection and the reconstruction of gravitational-wave transients in the LIGO-Virgo-KAGRA data using weak assumptions on the astrophysical sources
… such as supernovae, isolated neutron stars, and cosmic strings. Burst searches also provide the reconstruction of the GW waveform with minimal assumptions, and are able to identify discrepancies between theoretical models and measured data, which may reveal new physics. A well-known software for …
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Global dynamics of the universe
… between black-hole solutions and circular cosmic strings. Assuming the existence of circular 1 cosmic string with deficit angle ranging between 0 and 211", we are able to construct a class of non-trivial vacuum solutions with properties similar to black-hole solutions but with a more …