1,519 research outputs found
Wormholes, naked singularities and universes of ghost radiation
Both the static and homogeneous metrics describing the spherically symmetric
gravitational field of a crossflow of incoming and outgoing null dust streams
are generalized for the case of the two-component ghost radiation. Static
solutions represent either naked singularities or the wormholes recently found
by Hayward. The critical value of the parameter separating the two
possibilities is given. The wormhole is allowed to have positive mass. The
homogeneous solutions are open universes.Comment: 5 pages, 10 figures, minor changes to match the published versio
Quark number scaling in fluid dynamics and hadronization via quarkyonic matter
NCQ scaling of elliptic flow is studied in a non-equilibrium hadronization and freeze-out model from ideal, deconfined and chirally symmetric Quark Gluon Plasma (QGP), to final non-interacting hadrons. In this transition the quarks gain constituent quark mass while the background Bag-field breaks up. The constituent quarks then recombine into simplified hadron states, while chemical, thermal and flow equilibrium break down. Then the resulting temperatures and flow velocities of baryons and mesons will be different. In a simplified model, we reproduce the constituent quark number scaling
Constraining Ho\v{r}ava-Lifshitz gravity by weak and strong gravitational lensing
We discuss gravitational lensing in the Kehagias-Sfetsos space-time emerging
in the framework of Ho\v{r}ava-Lifshitz gravity. In weak lensing we show that
there are three regimes, depending on the value of , where is the Ho\v{r}ava-Lifshitz parameter and
characterizes the lensing geometry. When is close to zero,
light deflection typically produces two images, as in Schwarzschild lensing.
For very large the space-time approaches flatness, therefore
there is only one undeflected image. In the intermediate range of only the upper focused image is produced due to the existence of a
maximal deflection angle , a feature inexistent in the
Schwarzschild weak lensing. We also discuss the location of Einstein rings, and
determine the range of the Ho\v{r}ava-Lifshitz parameter compatible with
present day lensing observations. Finally, we analyze in the strong lensing
regime the first two relativistic Einstein rings and determine the constraints
on the parameter range to be imposed by forthcoming experiments.Comment: 11 pages, 6 figures, introductory part and reference list changed on
referee request, results expanded. Published versio
An exponential lower bound for Individualization-Refinement algorithms for Graph Isomorphism
The individualization-refinement paradigm provides a strong toolbox for
testing isomorphism of two graphs and indeed, the currently fastest
implementations of isomorphism solvers all follow this approach. While these
solvers are fast in practice, from a theoretical point of view, no general
lower bounds concerning the worst case complexity of these tools are known. In
fact, it is an open question whether individualization-refinement algorithms
can achieve upper bounds on the running time similar to the more theoretical
techniques based on a group theoretic approach.
In this work we give a negative answer to this question and construct a
family of graphs on which algorithms based on the individualization-refinement
paradigm require exponential time. Contrary to a previous construction of
Miyazaki, that only applies to a specific implementation within the
individualization-refinement framework, our construction is immune to changing
the cell selector, or adding various heuristic invariants to the algorithm.
Furthermore, our graphs also provide exponential lower bounds in the case when
the -dimensional Weisfeiler-Leman algorithm is used to replace the standard
color refinement operator and the arguments even work when the entire
automorphism group of the inputs is initially provided to the algorithm.Comment: 21 page
A Török Köztársaság az átalakuló Közel-Keleten = The Republic of Turkey in the changing Middle East
A 2011–2012-ben zajlott, „arab tavasznak” nevezett események új korszak kezdetét jelezték a Közel-Keleten, mely a hidegháború vége óta, de különösen a 2003-as iraki háború következtében amúgy is mélyreható átalakulási folyamaton megy keresztül. Ennek során a térség három nem arab állama, Izrael, Irán és Törökország
vált a régió hatalmi egyensúlyának meghatározó erőközpontjává, miközben az arab
országok – amúgy sem homogén – csoportja a háttérbe szorult. A korábban mértékadó
arab államok (Egyiptom, Irak, Szíria) különböző okok miatt elveszítették vonzerejüket
a többiek számára, miközben Szaúd-Arábia sem vállalta a vezető szerepét. Az „arab
tavasz” során egymástól egyre nyilvánvalóbban független nemzetállammá vált arab országok mind kevesebb kérdésben hajlandók közös álláspontot képviselni a nemzetközi fórumokon. Az átalakuló közel-keleti regionális rendben azonban az államok viszonylagos hatalmi egyensúlyában bekövetkezett változások miatt a térség helyzetét meghatározó szereplők száma megnövekedett, hiszen legalább Egyiptommal és Szaúd-Arábiával ismét mint politikai központtal kell számolni. A jelen tanulmány az e regionális
rendben sokak szerint neooszmán hegemón törekvésekkel fellépő Törökország helyét és szerepét vizsgálja
Quantum chaos in one dimension?
In this work we investigate the inverse of the celebrated
Bohigas-Giannoni-Schmit conjecture. Using two inversion methods we compute a
one-dimensional potential whose lowest N eigenvalues obey random matrix
statistics. Our numerical results indicate that in the asymptotic limit,
N->infinity, the solution is nowhere differentiable and most probably nowhere
continuous. Thus such a counterexample does not exist.Comment: 7 pages, 10 figures, minor correction, references extende
Transgenic fat-1 mouse as a model to study the pathophysiology of cardiovascular, neurological and psychiatric disorders
Polyunsaturated fatty acids (PUFAs) form an important constituent of all the cell membranes in the body. PUFAs such as arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) form precursors to both pro-inflammatory and anti-inflammatory compounds. Low-grade systemic inflammation occurs in clinical conditions such as insulin resistance, hypertension, type 2 diabetes mellitus, atherosclerosis, coronary heart disease, lupus, schizophrenia, Alzheimer's disease, and other dementias, cancer and non-alcoholic fatty liver disease (NAFLD) that are also characterized by an alteration in the metabolism of essential fatty acids in the form of excess production of pro-inflammatory eicosanoids and possibly, decreased synthesis and release of anti-inflammatory lipoxins, resolvins, protectins and maresins. We propose that low-grade systemic inflammation observed in these clinical conditions is due to an imbalance in the metabolism of essential fatty acids that is more in favour of pro-inflammatory molecules. In this context, transgenic fat-1 mouse that is designed to convert n-6 to n-3 fatty acids could form an ideal model to study the altered metabolism of essential fatty acids in the above mentioned conditions. It is envisaged that low-grade systemic inflammatory conditions are much less likely in the fat-1 mouse and/or these diseases will run a relatively mild course. Identifying the anti-inflammatory compounds from n-3 fatty acids that suppress low-grade systemic inflammatory conditions and understanding their mechanism(s) of action may lead to newer therapeutic strategies
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