109,201 research outputs found
Gaussian Effective Potential and the Coleman's normal-ordering Prescription : the Functional Integral Formalism
For a class of system, the potential of whose Bosonic Hamiltonian has a
Fourier representation in the sense of tempered distributions, we calculate the
Gaussian effective potential within the framework of functional integral
formalism. We show that the Coleman's normal-ordering prescription can be
formally generalized to the functional integral formalism.Comment: 6 pages, revtex; With derivation details and an example added. To
appear in J. Phys.
Penrose Limits of Non-standard Brane Intersections
The non-standard intersection of two 5-branes and a string can give rise to
AdS_3\times S^3\times S^3\times S^1. We consider the Penrose limit of this
geometry and study the supersymmetry of the resulting pp-wave solution. There
is a one-parameter family of Penrose limits associated with the orthogonal
rotation of the two foliating circles within the two 3-spheres. Supernumerary
Killing spinors arise only when the rotation angle is 45 degrees, for which
case we obtain the corresponding light-cone string action that has
linearly-realised supersymmetry. We also obtain Penrose limits of other
non-standard intersections that give rise to the product of AdS_3 or AdS_2 and
two spheres. The resulting pp-waves are supported by multiple constant field
strengths.Comment: Latex, 15 pages, references adde
Diffraction of a pulse by a three-dimensional corner
Three dimensional diffraction of sonic booms by corners of structure
S^1-wrapped D3-branes on Conifolds
We construct a D3-brane wrapped on S^1, which is fibred over the resolved
conifold as its transverse space. Whereas a fractional D3-brane on the resolved
conifold is not supersymmetric and has a naked singularity, our solution is
supersymmetric and regular everywhere. We also consider an -wrapped
D3-brane on the resolved cone over T^{1,1}/Z_2, as well as on the deformed
conifold. In the former case, we obtain a regular supergravity dual to a
certain four-dimensional field theory whose Lorentz and conformal symmetries
are broken in the IR region and restored in the UV limit.Comment: Latex, 14 pages, minor correction
Smooth Cosmologies from M-theory
We review two ways in which smooth cosmological evolution between two de
Sitter phases can be obtained from M/string-theory. Firstly, we perform a
hyperbolic reduction of massive IIA* theory to D=6 N=(1,1) SU(2)xU(1) gauged de
Sitter supergravity, which supports smooth cosmological evolution between dS_4
x S^2 and a dS_6-type geometry. Secondly, we obtain four-dimensional de Sitter
gravity with SU(2) Yang-Mills gauge fields from a hyperbolic reduction of
standard eleven-dimensional supergravity. The four-dimensional theory supports
smooth cosmological evolution between dS_2 x S^2 and a dS_4-type geometry.
Although time-dependent, these solutions arise from a first-order system via a
superpotential construction. For appropriate choices of charges, these
solutions describe an expanding universe whose expansion rate is significantly
larger in the past than in the future, as required for an inflationary model.Comment: Latex, 7 pages, Contribution to Quantum Theory and Symmetries
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