6,231 research outputs found
Wormholes in Two Dimensional Dilaton Gravity
It is shown that the general solution of classical equations of motion in two
dimensional dilaton gravity proposed by Callan, Giddings, Harvey and Strominger
(CGHS) includes a Lorentzian wormhole solution in addition to a black hole
solution. We also show that matter perturbation of the wormhole by a shock wave
leads to the formation of a black hole where the curvature singularity is
cloaked by the global event horizon. It is also argued that the classical
wormhole would be stable against quantum corrections.Comment: INS-Rep.-1012, NDA-FP-13/93, OCHA-PP-37, LATEX file, 9p
Higgs Mechanism for Gravitons
Just like the vector gauge bosons in the gauge theories, it is now known that
gravitons acquire mass in the process of spontaneous symmetry breaking of
diffeomorphisms through the condensation of scalar fields. The point is that we
should find the gravitational Higgs mechanism such that it results in massive
gravity in a flat Minkowski space-time without non-unitary propagating modes.
This is usually achieved by including higher-derivative terms in scalars and
tuning the cosmological constant to be a negative value in a proper way.
Recently, a similar but different gravitational Higgs mechanism has been
advocated by Chamseddine and Mukhanov where one can relax the negative
cosmological constant to zero or positive one. In this work, we investigate why
the non-unitary ghost mode decouples from physical Hilbert space in a general
space-time dimension. Moreover, we generalize the model to possess an arbitrary
potential and clarify under what conditions the general model exhibits the
gravitational Higgs mechanism. By searching for solutions to the conditions, we
arrive at two classes of potentials exhibiting gravitational Higgs mechanism.
One class includes the model by Chamseddine and Mukhanov in a specific case
while the other is completely a new model.Comment: 11 page
Locally Localized Gravity Models in Higher Dimensions
We explore the possibility of generalizing the locally localized gravity
model in five space-time dimensions to arbitrary higher dimensions. In a
space-time with negative cosmological constant, there are essentially two kinds
of higher-dimensional cousins which not only take an analytic form but also are
free from the naked curvature singularity in a whole bulk space-time. One
cousin is a trivial extension of five-dimensional model, while the other one is
in essence in higher dimensions. One interesting observation is that in the
latter model, only anti-de Sitter () brane is physically meaningful
whereas de Sitter () and Minkowski () branes are dismissed.
Moreover, for brane in the latter model, we study the property of
localization of various bulk fields on a single brane. In particular, it is
shown that the presence of the brane cosmological constant enables bulk gauge
field and massless fermions to confine to the brane only by a gravitational
interaction. We find a novel relation between mass of brane gauge field and the
brane cosmological constant.Comment: 20 pages, LaTex 2e, revised version (to appear in Phys. Rev. D
On Unitarity of Massive Gravity in Three Dimensions
We examine a unitarity of a particular higher-derivative extension of general
relativity in three space-time dimensions, which has been recently shown to be
equivalent to the Pauli-Fierz massive gravity at the linearized approximation
level, and explore a possibility of generalizing the model to higher space-time
dimensions. We find that the model in three dimensions is indeed unitary in the
tree-level, but the corresponding model in higher dimensions is not so due to
the appearance of non-unitary massless spin-2 modes.Comment: 10 pages, references adde
Hamiltonian Analysis of the Higgs Mechanism for Graviton
In this paper we perform the canonical description of the Higgs mechanism for
gravity and provide the Hamiltonian definition of the massive gravities.Comment: 18 page
On zero modes of the eleven dimensional superstring
It is shown that recently pointed out by Berkovits on-shell degrees of
freedom of the D=11 superstring do not make contributions into the quantum
states spectrum of the theory. As a consequence, the spectrum coincides with
that of the D=10 type IIA superstring.Comment: 7 pages, LaTex fil
Bosonic Fields in the String-like Defect Model
We study localization of bosonic bulk fields on a string-like defect with
codimension 2 in a general space-time dimension in detail. We show that in
cases of spin 0 scalar and spin 1 vector fields there are an infinite number of
massless Kaluza-Klein (KK) states which are degenerate with respect to the
radial quantum number, but only the massless zero mode state among them is
coupled to fermion on the string-like defect. It is also commented on
interesting extensions of the model at hand to various directions such as
'little' superstring theory, conformal field theory and a supersymmetric
construction.Comment: 17 pages, LaTex 2e, revised version (to appear in Phys. Rev. D
Free Differential Algebras and Pure Spinor Action in IIB Superstring Sigma Models
In this paper we extend to the case of IIB superstring sigma models the
method proposed in hep-th/10023500 to derive the pure spinor approach for type
IIA sigma models. In particular, starting from the (Free) Differential Algebra
and superspace parametrization of type IIB supergravity, extended to include
the BRST differential and all the ghosts, we derive the BRST transformations of
fields and ghosts as well as the standard pure spinor constraints for the
ghosts related to supersymmetry. Moreover, using the method first
proposed by us, we derive the pure spinor action for type IIB superstrings in
curved supergravity backgrounds (on shell), in full agreement with the action
first obtained by Berkovits and Howe.Comment: 24 page
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