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2. Half BPS states in AdS[sub]5 x Y[sup]p,qEdi Gava, Giuseppe Milanesi, Kumar S. Narain, Martin O'Loughlin, 2008, original scientific article Found in: osebi
Keywords: modeli, supergravitacija, teorija strun, holografija
Published: 15.10.2013; Views: 5110; Downloads: 19
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5. Horizon Shells and BMS-like soldering transformationsMartin O'Loughlin, Matthias Blau, 2016, original scientific article Abstract: We revisit the theory of null shells in general relativity, with a particular
emphasis on null shells placed at horizons of black holes. We study in detail the considerable
freedom that is available in the case that one solders two metrics together across null
hypersurfaces (such as Killing horizons) for which the induced metric is invariant under
translations along the null generators. In this case the group of soldering transformations
turns out to be infinite dimensional, and these solderings create non-trivial horizon shells
containing both massless matter and impulsive gravitational wave components. We also
rephrase this result in the language of Carrollian symmetry groups. To illustrate this
phenomenon we discuss in detail the example of shells on the horizon of the Schwarzschild
black hole (with equal interior and exterior mass), uncovering a rich classical structure
at the horizon and deriving an explicit expression for the general horizon shell energy-
momentum tensor. In the special case of BMS-like soldering supertranslations we find a
conserved shell-energy that is strikingly similar to the standard expression for asymptotic
BMS supertranslation charges, suggesting a direct relation between the physical properties
of these horizon shells and the recently proposed BMS supertranslation hair of a black hole.
Found in: osebi
Keywords: Black Holes, Classical Theories of Gravity, Space-Time Symmetries
Published: 10.03.2016; Views: 3793; Downloads: 0
 Fulltext (333,17 KB) |
6. 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: osebi
Keywords: singular hypersurface, impulsive signal, gravitational wave, null geodesic, timelike (spacelike) geodesic
Published: 16.05.2016; Views: 6315; Downloads: 248
Fulltext (475,54 KB) |
7. 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: osebi
Keywords: Gravitational waves, Ligo, Binary black hole merger, gravitational
wave interferometry
Published: 27.09.2016; Views: 6011; Downloads: 294
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10. Strateško načrtovanje v dejavnosti turizma in gostinstva: študija primera turistične destinacije v izbrani mestni občiniMartin Bizjak, 2015, master's thesis Abstract: V magistrskem delu obravnavamo problematiko strateškega managementa v izbrani turistični destinaciji, ker smo na področju raziskovanja in predhodnega preučevanja omenjene problematike identificirali raziskovalno vrzel. Namen magistrskega dela je, na podlagi sistematičnega pregleda domače in tuje strokovne literature ter zasnovi konceptualnega modela strategije razvoja turizma, empirično preveriti stopnjo razvitosti strateškega načrtovanja turistične in gostinske dejavnosti v izbrani turistični destinaciji ter podati morebitne predloge za izboljšanje stanja.
Za empirični del raziskave smo uporabili kvalitativno metodo raziskovanja in oblikovali raziskovalna vprašanja ter nato opravili intervju s štirimi predstavniki turističnih ponudnikov in tremi predstavniki organizacij, ki so vpete v lokalni turizem. Ugotovili smo, da tako konkurenčne prednosti kot družbena odgovornost in vrednote statistično značilno vplivajo na uspešnost turističnega podjetja. Izidi iz raziskave predstavljajo prispevek k širšemu vpogledu na strateški management v turizmu ter bodo uporabni za vse tiste, ki se teoretično, raziskovalno ali strokovno ukvarjajo s to dejavnostjo.
Found in: osebi
Keywords: Management, organizacija, raziskava, strateški management, turistična destinacija
Published: 29.09.2015; Views: 5574; Downloads: 448
Fulltext (1,06 MB) |
