6,694 research outputs found
Holst Actions for Supergravity Theories
Holst action containing Immirzi parameter for pure gravity is generalised to
the supergravity theories. Supergravity equations of motion are not modified by
such generalisations, thus preserving supersymmetry. Dependence on the Immirzi
parameter does not emerge in the classical equations of motion. This is in
contrast with the recent observation of Perez and Rovelli for gravity action
containing original Holst term and a minimally coupled Dirac fermion where the
classical equations of motion do develop a dependence on Immirzi parameter.Comment: 15 page
Spin nematic ground state of the triangular lattice S=1 biquadratic model
Motivated by the spate of recent experimental and theoretical interest in
Mott insulating S=1 triangular lattice magnets, we consider a model S=1
Hamiltonian on a triangular lattice interacting with rotationally symmetric
biquadratic interactions. We show that the partition function of this model can
be expressed in terms of configurations of three colors of tightly-packed,
closed loops with {\em non-negative} weights, which allows for efficient
quantum Monte Carlo sampling on large lattices. We find the ground state has
spin nematic order, i.e. it spontaneously breaks spin rotation symmetry but
preserves time reversal symmetry. We present accurate results for the
parameters of the low energy field theory, as well as finite-temperature
thermodynamic functions
Polymorphous low grade adenocarcinoma-an unusual presentation
Polymorphous low-grade adenocarcinoma (PLGA) is a neoplasm that occurs frequently in the mucosa of the soft and hard palates, in the buccal mucosa and in the upper lip and is very rare within the nasopharynx. We present a case of PLGA, which presented as a nasal polyp
Metals get an awkward cousin
A newly predicted state of matter is a simple theoretical example of a phase
that conducts electricity but is not smoothly connected to our conventional
model of metals. A viewpoint on arXiv:1201.5998.Comment: Physics 5, 82 (2012
Logarithmic correction to the Bekenstein-Hawking entropy of the BTZ black hole
We derive an exact expression for the partition function of the Euclidean BTZ
black hole. Using this, we show that for a black hole with large horizon area,
the correction to the Bekenstein-Hawking entropy is , in
agreement with that for the Schwarzschild black hole obtained in the canonical
gravity formalism and also in a Lorentzian computation of BTZ black hole
entropy. We find that the right expression for the logarithmic correction in
the context of the BTZ black hole comes from the modular invariance associated
with the toral boundary of the black hole.Comment: LaTeX, 10 pages, typos corrected, clarifications adde
Black Hole Entropy from a Highly Excited Elementary String
Suggested correspondence between a black hole and a highly excited elementary
string is explored. Black hole entropy is calculated by computing the density
of states for an open excited string. We identify the square root of oscillator
number of the excited string with Rindler energy of black hole to obtain an
entropy formula which, not only agrees at the leading order with the
Bekenstein-Hawking entropy, but also reproduces the logarithmic correction
obtained for black hole entropy in the quantum geometry framework. This
provides an additional supporting evidence for correspondence between black
holes and strings.Comment: revtex, 4 page
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