1,844 research outputs found
Hom-Lie color algebra structures
This paper introduces the notion of Hom-Lie color algebra, which is a natural
general- ization of Hom-Lie (super)algebras. Hom-Lie color algebras include
also as special cases Lie (super) algebras and Lie color algebras. We study the
homomorphism relation of Hom-Lie color algebras, and construct new algebras of
such kind by a \sigma-twist. Hom-Lie color admissible algebras are also defined
and investigated. They are finally classified via G-Hom-associative color
algebras, where G is a subgroup of the symmetric group S_3.Comment: 16 page
Cosmological Constant and Noncommutativity: A Newtonian point of view
We study a Newtonian cosmological model in the context of a noncommutative
space. It is shown that the trajectories of a test particle undergo
modifications such that it no longer satisfies the cosmological principle. For
the case of a positive cosmological constant, spiral trajectories are obtained
and corrections to the Hubble constant appear. It is also shown that, in the
limit of a strong noncommutative parameter, the model is closely related to a
particle in a G\"odel-type metric.Comment: 14 pages, 3 figures, Introduction was changed and references added.
Final version accepted for publication in JMPL
Bits and Pieces in Logarithmic Conformal Field Theory
These are notes of my lectures held at the first School & Workshop on
Logarithmic Conformal Field Theory and its Applications, September 2001 in
Tehran, Iran.
These notes cover only selected parts of the by now quite extensive knowledge
on logarithmic conformal field theories. In particular, I discuss the proper
generalization of null vectors towards the logarithmic case, and how these can
be used to compute correlation functions. My other main topic is modular
invariance, where I discuss the problem of the generalization of characters in
the case of indecomposable representations, a proposal for a Verlinde formula
for fusion rules and identities relating the partition functions of logarithmic
conformal field theories to such of well known ordinary conformal field
theories.
These two main topics are complemented by some remarks on ghost systems, the
Haldane-Rezayi fractional quantum Hall state, and the relation of these two to
the logarithmic c=-2 theory.Comment: 91 pages, notes of lectures delivered at the first School and
Workshop on Logarithmic Conformal Field Theory and its Applications, Tehran,
September 2001. Amendments in Introductio
U(1) Gauge Field of the Kaluza-Klein Theory in the Presence of Branes
We investigate the zero mode dimensional reduction of the Kaluza-Klein
unifications in the presence of a single brane in the infinite extra dimension.
We treat the brane as fixed, not a dynamical object, and do not require the
orbifold symmetry. It seems that, contrary to the standard Kaluza-Klein models,
the 4D effective action is no longer invariant under the U(1) gauge
transformations due to the explicit breaking of isometries in the extra
dimension by the brane. Surprisingly, however, the linearized perturbation
analysis around the RS vacuum shows that the Kaluza-Klein gauge field does
possess the U(1) gauge symmetry at the linear level. In addition, the
graviscalar also behaves differently from the 4D point of view. Some physical
implications of our results are also discussed.Comment: 10 pages, revtex, no figure, version to appear in Phys. Rev. D,
possible caveats of our results due to the zero mode ansatz we used are
explained in more detai
Dynamical Behavior of the BTZ Black Hole
We study the dynamical behavior of the BTZ (Banados-Teitelboim-Zanelli) black
hole with the low-energy string effective action. The perturbation analysis
around the BTZ black hole reveals a mixing between the dilaton and other
fields. Introducing the new gauge (dilaton gauge), we disentangle this mixing
completely and obtain one decoupled dilaton equation. We obtain the decay rate
of BTZ black hole.Comment: minor typhographical corrections, ReVTeX, 9 pages with no figure
Thermodynamics of phase transition in higher dimensional AdS black holes
We investigate the thermodynamics of phase transition for
dimensional Reissner Nordstrom (RN)-AdS black holes using a grand canonical
ensemble. This phase transition is characterized by a discontinuity in specific
heat. The phase transition occurs from a lower mass black hole with negative
specific heat to a higher mass black hole with positive specific heat. By
exploring Ehrenfest's scheme we show that this is a second order phase
transition. Explicit expressions for the critical temperature and critical mass
are derived. In appropriate limits the results for dimensional
Schwarzschild AdS black holes are obtained.Comment: LaTex, 11 pages, 5 figures, To appear in JHE
Dissipative cosmological solutions
The exact general solution to the Einstein equations in a homogeneous
Universe with a full causal viscous fluid source for the bulk viscosity index
is found. We have investigated the asymptotic stability of Friedmann
and de Sitter solutions, the former is stable for and the latter for
. The comparison with results of the truncated theory is made. For
, it was found that families of solutions with extrema no longer remain
in the full case, and they are replaced by asymptotically Minkowski evolutions.
These solutions are monotonic.Comment: 17 pages, LaTeX 2.09, 1 figure. To be published in Classical and
Quantum Gravit
Brane World Cosmology with Gauss-Bonnet Interaction
We study a Randall-Sundrum model modified by a Gauss-Bonnet interaction term.
We consider, in particular, a Friedmann-Robertson-Walker metric on the brane
and analyse the resulting cosmological scenario. It is shown that the usual
Friedmann equations are recovered on the brane. The equation of state relating
the enery density and the pressure is uniquely determined by the matching
conditions. A cosmological solution with negative pressure is found.Comment: 9 pages, revtex styl
The Globular Cluster System of M60 (NGC 4649). II. Kinematics of the Globular Cluster System
We present a kinematic analysis of the globular cluster (GC) system in the
giant elliptical galaxy (gE) M60 in the Virgo cluster. Using the photometric
and spectroscopic database of 121 GCs (83 blue GCs and 38 red GCs), we have
investigated the kinematics of the GC system. We have found that the M60 GC
system shows a significant overall rotation. The rotation amplitude of the blue
GCs is slightly smaller than or similar to that of the red GCs, and their
angles of rotation axes are similar. The velocity dispersions about the mean
velocity and about the best fit rotation curve for the red GCs are marginally
larger than those for the blue GCs. Comparison of observed stellar and GC
velocity dispersion profiles with those calculated from the stellar mass
profile shows that the mass-to-light ratio should be increased as the
galactocentric distance increases, indicating the existence of an extended dark
matter halo. The entire sample of GCs in M60 is found to have a tangentially
biased velocity ellipsoid unlike the GC systems in other gEs. Two subsamples
appear to have different velocity ellipsoids. The blue GC system has a modest
tangentially biased velocity ellipsoid, while the red GC system has a modest
radially biased or an isotropic velocity ellipsoid. From the comparison of the
kinematic properties of the M60 GC system to those of other gEs (M87, M49, NGC
1399, NGC 5128, and NGC 4636), it is found that the velocity dispersion of the
blue GC system is similar to or larger than that of the red GC system except
for M60, and the rotation of the GC system is not negligible. The entire sample
of each GC system shows an isotropic velocity ellipsoid except for M60, while
the subsamples show diverse velocity ellipsoids. We discuss the implication of
these results for the formation models of the GC system in gEs.Comment: 48 pages, 16 figures. To appear in Ap
Horava-Lifshitz Holography
We derive the detailed balance condition as a solution to the Hamilton-Jacobi
equation in the Horava-Lifshitz gravity. This result leads us to propose the
existence of the d-dimensional quantum field theory on the future boundary of
the (d+1)-dimensional Horava-Lifshitz gravity from the viewpoint of the
holographic renormalization group. We also obtain a Ricci flow equation of the
boundary theory as the holographic RG flow, which is the Hamilton equation in
the bulk gravity, by tuning parameters in the theory.Comment: 7 page
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