1. Properties of Null HypersurfacesHovhannes Demirtshyan, 2016, master's thesis Abstract: The aim of this thesis is to investigate the effects that a lightlike singular hypersurface can have on a congruence of timelike (spacelike) geodesics and to extend the existing theory to the case of null geodesics.
The introduction discusses the applications of singular hypersurfaces for the description of physical phenomena, their major classfications and includes a short discussion of the two theoretical approaches that exist to study singular hypersurfaces. The second chapter contains detailed description of these approaches. The theoretical frameworks for both cases of lightlike and timelike (spacelike) hypersurfaces are developed. This chapter also discusses the application of these theories to the case when the hypersurface contains a plane fronted lightlike signal.
The final chapter starts with a discussion of the effects that a lightlike singular hypersurface can have on a congruence of timelike (spacelike) geodesics. A new approach to these calculations is presented together with an extension of the theory to the case of a congruence of null geodesics. At
the end of the chapter a concrete example and its similarities with the case of timelike geodesics is discussed.
In conclusion, the thesis suggests a new mathematical framework for describing a congruence of null geodesics crossing a singular null hypersurface. The results may be applied in experimental physics to detect impulsive signals which are located in singular null hypersurfaces and to this end there
is a discussion of the properties and possibilities for a detector of impulsive lightlike signals, which include gravitational waves.
Found in: ključnih besedah
Summary of found: ...detector of impulsive lightlike signals, which include gravitational waves.... ...singular hypersurface, impulsive signal, gravitational wave,null geodesic, timelike (spacelike) geodesic...
Keywords: singular hypersurface, impulsive signal, gravitational wave, null geodesic, timelike (spacelike) geodesic
Published: 16.05.2016; Views: 6481; Downloads: 252
 Fulltext (475,54 KB) |
2. Detection of gravitational wavesGregor Mrak, 2016, undergraduate thesis Abstract: This report mainly focuses on the first two detections of gravitational waves
(GW). At the beginning of the thesis the historical background of GW explorations
is discussed by pointing out some arguments and researchers
that were essential for the progress. Continuing with the derivation based
on the theory of general relativity, in order to express where certain properties
derive. In the main part of the report, the subject of interest becomes
Laser interferometer gravitational-wave observatory (LIGO), beginning
with the problems occurring on the way to detection, describing different
noise sources one by one. After pointing out the problems, solutions
are discussed, namely the technological advances made to lower the background
noise as much as possible. The chapter (4) points out different parts
of the detector which are implemented to produce a clearer signal. As only
physical noise reduction methods are not enough, digital signal processing
algorithms are mentioned as well which are used to analyze the data. Subsequently
the required theoretical knowledge is given, so the main part ends
with the analysis of actual data taken from LIGO’s public release for both
GW150914 and GW151226 events (first and second official detections). In
the conclusion of the report a brief descriptions of various detectors besides
Ligo are given and some insight of the future detectors that are planned to
be built.
Found in: ključnih besedah
Summary of found: ...on the first two detections of gravitational waves
(GW). At the beginning of the thesis the...
Keywords: Gravitational waves, Ligo, Binary black hole merger, gravitational
wave interferometry
Published: 27.09.2016; Views: 6174; Downloads: 303
Fulltext (3,27 MB) |
3. Multi-messenger study with the Pierre Auger ObservatoryLili Yang, unpublished invited conference lecture Abstract: The Pierre Auger Observatory is the largest cosmic ray detector in the world, studying particles with energy above 10^17 eV. Even though Auger is dedicated to charged cosmic rays, it’s also sensitive to ultra-high energy neutral particles, such as photons, neutrinos and neutrons, which are undeflected by magnetic field and pointing back to the source site. More exciting, with the breakthrough observations of gravitational-wave signal, the new era of multi-messenger analysis has come. I will present the recent results and prospects of multi-messenger study with Auger and also the first joint detection of gravitational and electromagnetic radiation from the source, with a focus on the UHE neutrino search.
Found in: ključnih besedah
Summary of found: ...More exciting, with the breakthrough observations of gravitational-wave signal, the new era of multi-messenger analysis...
Keywords: Pierre Auger Observatory, multi-messenger, neutrino, gravitational wave
Published: 17.01.2018; Views: 3307; Downloads: 0
Fulltext (9,04 MB) |
4. Follow-up searches for ultra-high energy neutrinos from transient astrophysical sources with the Pierre Auger ObservatoryLukas Zehrer, Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Marta Trini, Samo Stanič, Gašper Kukec Mezek, Andrej Filipčič, Michael Schimp, 2019, published scientific conference contribution Found in: ključnih besedah
Summary of found: ...Observatory, transient astrophysical sources,
binary black hole mergers, gravitational wave events, blazar TXS 0506+056, follow-up search...
Keywords: Pierre Auger Observatory, transient astrophysical sources, binary black hole mergers, gravitational wave events, blazar TXS 0506+056, follow-up search for counterpart ultra-high energy neutrinos
Published: 21.12.2020; Views: 1805; Downloads: 64
Fulltext (366,82 KB) |
