1,815 research outputs found
Friedmann universe with dust and scalar field
We study a spatially flat Friedmann model containing a pressureless perfect
fluid (dust) and a scalar field with an unbounded from below potential of the
form V(\fii)=W_0 - V_0\sinh(\sqrt{3/2}\kappa\fii), where the parameters
and are arbitrary and . The model is
integrable and all exact solutions describe the recollapsing universe. The
behavior of the model near both initial and final points of evolution is
analyzed. The model is consistent with the observational parameters. We single
out the exact solution with the present-day values of acceleration parameter
and dark matter density parameter describing
the evolution within the time approximately equal to .Comment: 11 pages, 10 figure
Black Holes in AdS/BCFT and Fluid/Gravity Correspondence
A proposal to describe gravity duals of conformal theories with boundaries
(AdS/BCFT correspondence) was put forward by Takayanagi few years ago. However
interesting solutions describing field theories at finite temperature and
charge density are still lacking. In this paper we describe a class of theories
with boundary, which admit black hole type gravity solutions. The theories are
specified by stress-energy tensors that reside on the extensions of the
boundary to the bulk. From this perspective AdS/BCFT appears analogous to the
fluid/gravity correspondence. Among the class of the boundary extensions there
is a special (integrable) one, for which the stress-energy tensor is
fluid-like. We discuss features of that special solution as well as its
thermodynamic properties.Comment: 18 pages, 4 figures (7 pdf-files). Save and view with Adobe Reader if
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QCD corrections to tri-boson production
We present a computation of the next-to-leading order QCD corrections to the
production of three Z bosons at the LHC. We calculate these corrections using a
completely numerical method that combines sector decomposition to extract
infrared singularities with contour deformation of the Feynman parameter
integrals to avoid internal loop thresholds. The NLO QCD corrections to pp ->
ZZZ are approximately 50%, and are badly underestimated by the leading order
scale dependence. However, the kinematic dependence of the corrections is
minimal in phase space regions accessible at leading order.Comment: 15 pages, 3 figures; typos fixed, references and event listing adde
Complete description of polarization effects in emission of a photon by an electron in the field of a strong laser wave
We consider emission of a photon by an electron in the field of a strong
laser wave. Polarization effects in this process are important for a number of
physical problems. A probability of this process for circularly or linearly
polarized laser photons and for arbitrary polarization of all other particles
is calculated. We obtain the complete set of functions which describe such a
probability in a compact invariant form. Besides, we discuss in some detail the
polarization effects in the kinematics relevant to the problem of electron to
photon conversion at photon-photon and photon-electron colliders.Comment: 18 pages, minor changes, published versio
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