5,826 research outputs found
Exact Solutions in Five-Dimensional Axi-dilaton Gravity with Euler-Poincare Term
We examine the effective field equations that are obtained from the
axi-dilaton gravity action with a second order Euler-Poincare term and a
cosmological constant in all higher dimensions. We solve these equations for
five-dimensional spacetimes possessing homogeneity and isotropy in their
three-dimensional subspaces. For a number of interesting special cases we show
that the solutions fall into two main classes: The first class consists of
time-dependent solutions with spherical or hyperboloidal symmetry which require
certain fine-tuning relations between the coupling constants of the model and
the cosmological constant. Solutions in the second class are locally static and
prove the validity of Birkhoff's staticity theorem in the axi-dilaton gravity.
We also give a special class of static solutions, among them the well-known
black hole solutions in which the usual electric charge is superseded by an
axion charge.Comment: New formulas and references adde
The scalar unparticle effect on the charged lepton electric dipole moment
We study the charged lepton electric dipole moment which is induced by the
scalar unparticle mediation and we predict the appropriate range for the free
parameters appearing in the effective lagrangian which drives the
unparticle-standard model lepton interactions. We observe that the charged
lepton electric dipole moment is strongly sensitive to the scaling dimension
d_u of the unparticle and the new couplings in the effective interaction.
Furthermore, we see that the current experimental limits of charged lepton
electric dipole moments can ensure an appropriate range for these free
parameters.Comment: 19 pages, 13 Figure
The complete set of solutions of the geodesic equations in the space-time of a Schwarzschild black hole pierced by a cosmic string
We study the geodesic equations in the space-time of a Schwarzschild black
hole pierced by an infinitely thin cosmic string and give the complete set of
analytical solutions of these equations for massive and massless particles,
respectively. The solutions of the geodesic equations can be classified
according to the particle's energy and angular momentum, the ratio between the
component of the angular momentum aligned with the axis of the string and the
total angular momentum, the deficit angle of the space-time and as well the
horizon radius (or mass) of the black hole. For bound orbits of massive test
particles we calculate the perihelion shift, we discuss light deflection and
comment on the Newtonian limit.Comment: 21 pages; section 3 shortened, references added; accepted for
publication in Phys. Rev.
Geodesic motion in the space-time of cosmic strings interacting via magnetic fields
We study the geodesic motion of test particles in the space-time of two
Abelian-Higgs strings interacting via their magnetic fields. These bound states
of cosmic strings constitute a field theoretical realization of p-q-strings
which are predicted by inflationary models rooted in String Theory, e.g. brane
inflation. In contrast to previously studied models describing p-q-strings our
model possesses a Bogomolnyi-Prasad-Sommerfield (BPS) limit. If cosmic strings
exist it would be exciting to detect them by direct observation. We propose
that this can be done by the observation of test particle motion in the
space-time of these objects. In order to be able to make predictions we have to
solve the field equations describing the configuration as well as the geodesic
equation numerically. The geodesics can then be classified according to the
test particle's energy, angular momentum and momentum along the string axis. We
find that the interaction of two Abelian-Higgs strings can lead to the
existence of bound orbits that would be absent without the interaction. We also
discuss the minimal and maximal radius of orbits and comment on possible
applications in the context of gravitational wave emission.Comment: v1: 22 pages including 17 figures; v2: new figure added, section on
observables added; acccepted for publication in Phys. Rev.
Vacuum Fluctuations of a massless spin-1/2 field around multiple cosmic strings
We study the interaction of a massless quantized spinor field with the
gravitational filed of N parallel static cosmic strings by using a perturbative
approach. We show that the presence of more than one cosmic string gives rise
to an additional contribution to the energy density of vacuum fluctuations,
thereby leading to a vacuum force attraction between two parallel cosmic
strings.Comment: Class. Quantum Grav. 14(1997) 321
Investigation of heavy-heavy pseudoscalar mesons in thermal QCD Sum Rules
We investigate the mass and decay constant of the heavy-heavy pseudoscalar,
, and mesons in the framework of finite temperature QCD
sum rules. The annihilation and scattering parts of spectral density are
calculated in the lowest order of perturbation theory. Taking into account the
additional operators arising at finite temperature, the nonperturbative
corrections are also evaluated. The masses and decay constants remain unchanged
under , but after this point, they start to diminish with
increasing the temperature. At critical or deconfinement temperature, the decay
constants reach approximately to 35% of their values in the vacuum, while the
masses are decreased about 7%, 12% and 2% for , and
states, respectively. The results at zero temperature are in a good consistency
with the existing experimental values as well as predictions of the other
nonperturbative approaches.Comment: 11 Pages, 2 Tables and 6 Figure
Dynamical systems of M\"obius transformation: real, -adic and complex variables
In this paper we consider function , (where ,
, ) on three fields: the set of real, -adic and
complex numbers. We study dynamical systems generated by this function on each
field separately and give some comparison remarks.
For real variable case we show that the real dynamical system of the function
depends on the parameters . Namely, we classify the
parameters to three sets and prove that: for the parameters from first class
each point, for which the trajectory is well defined, is a periodic point of
; for the parameters from second class any trajectory (under ) converges
to one of fixed points (there may be up to two fixed points); for the
parameters from third class any trajectory is dense in .
For the -adic variable we give a review of known results about dynamical
systems of function . Then using a recently developed method we give simple
new proofs of these results and prove some new ones related to trajectories
which do not converge.
For the complex variables we give a review of known results.Comment: 13 page
Topologically massive magnetic monopoles
We show that in the Maxwell-Chern-Simons theory of topologically massive
electrodynamics the Dirac string of a monopole becomes a cone in anti-de Sitter
space with the opening angle of the cone determined by the topological mass
which in turn is related to the square root of the cosmological constant. This
proves to be an example of a physical system, {\it a priory} completely
unrelated to gravity, which nevertheless requires curved spacetime for its very
existence. We extend this result to topologically massive gravity coupled to
topologically massive electrodynamics in the framework of the theory of Deser,
Jackiw and Templeton. These are homogeneous spaces with conical deficit. Pure
Einstein gravity coupled to Maxwell-Chern-Simons field does not admit such a
monopole solution
2,6-Bis(diphenylphosphinosulfide)pyridine (L) as a facial terdentate ligand: synthesis and characterisation of the tricarbonylrhenium(I) complexes fac-[Re(CO)âL]âș [Reâ(CO)â(”-X)â]â» (X = Cl, Br or I) and fac-[Re(CO)âL]âș[SbFâ]â».
The halogenopentacarbonylrhenium(I) compounds react with 2,6-bis(diphenylphosphinosulfide) pyridine (L) under mild conditions to yield ionic complexes of general formulae, fac-[Reâ(CO)âL]âș [Re2(CO) â(ÎŒ-X) )â]â» (X=Cl, Br or I), in which the ligand adopts a facial terdentate bonding mode. A synthesis of [Re(CO)âL]âș [SbFâ]â» was carried out to establish the presence of the cation, fac-[Re(CO)âL]âș, in the complexes. The character of the anions was confirmed by negative ion MALDI-TOF mass spectrometry. The cation is fluxional; the Pâphenyl rings oriented towards the metal moiety exhibit restricted rotation at low temperature. The free energy of activation, ÎG â , for hindered rotation is ca. 47 kJ molâ»Âč for all complexes. Solid-stateâ ÂčP NMR data are reported for the free ligand and for the complexes, [Re(CO)âL][SbFâ] and [Re(CO)âL][Reâ(CO)â(ÎŒ-X)â] (X=Cl, Br or I)
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