31,272 research outputs found
On M-Theory Embedding of Topologically Massive Gravity
We show that topologically massive gravity can be obtained by the consistent
Kaluza-Klein reduction from recently constructed seven-dimensional gravity with
topological terms. The internal four-manifold should be Einstein with the
Pontryagin four-form constantly proportional to the volume form. We also
discuss the possible lift of the system to D=11. This enables us to connect the
mass parameter \tilde\mu in D=3 to the M5-brane charge. The dimensionless
quantity 3/(G\tilde \mu) is discrete and proportional to N, where N is the
number of M5-branes.Comment: 8 pages, no figures, references added, version appeared in
Int.J.Mod.Phys.
Most General Spherically Symmetric M2-branes and Type IIB Strings
We obtain the most general spherically symmetric M2-branes and type IIB
strings, with \R^{1,2}\times SO(8) and \R^{1,1}\times SO(8) isometries
respectively. We find that there are twelve different classes of M2-branes, and
we study their curvature properties. In particular we obtain new smooth
M2-brane wormholes that connect two asymptotic regions: one is flat and the
other can be either flat or AdS_4\times S^7. We find that these wormholes are
traversable with certain time-like trajectories. We also obtain the most
general Ricci-flat solutions in five dimensions with \R^{1,1}\times SO(3)
isometries.Comment: 37 pages, 1 table, revised version to appear in PR
Exact Green's Function and Fermi Surfaces from Conformal Gravity
We study the Dirac equation of a charged massless spinor on the general
charged AdS black hole of conformal gravity. The equation can be solved exactly
in terms of Heun's functions. We obtain the exact Green's function in the phase
space (\omega,k). This allows us to obtain Fermi surfaces for both Fermi and
non-Fermi liquids. Our analytic results provide a more elegant approach of
studying some strongly interacting fermionic systems not only at zero
temperature, but also at any finite temperature. At zero temperature, we
analyse the motion of the poles in the complex \omega plane and obtain the
leading order terms of the dispersion relation, expressed as the Laurent
expansion of \omega in terms of k. We illustrate new distinguishing features
arising at the finite temperature. The Green's function with vanishing \omega
at finite temperature has a fascinating rich structure of spiked maxima in the
plane of k and the fermion charge q.Comment: 12 pages, typos corrected, further discussions on the properties of
the Green's function and dispersion relation, new figures of the motion of
poles added. Version to appear in Phys. Lett.
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