8,719 research outputs found
Multidimensional Geometrical Model of the Renormalized Electrical Charge with Splitting off the Extra Coordinates
A geometrical model of electric charge is proposed. This model has ``naked''
charge screened with a ``fur - coat'' consisting of virtual wormholes. The 5D
wormhole solution in the Kaluza - Klein theory is the ``naked'' charge. The
splitting off of the 5D dimension happens on the two spheres (null surfaces)
bounding this 5D wormhole. This allows one to sew two Reissner - Nordstr\"om
black holes onto it on both sides. The virtual wormholes entrap a part of the
electrical flux lines coming into the ``naked'' charge. This effect essentially
changes the charge visible at infinity so that it satisfies the real relation
.Comment: 10 pages, 1 figure, awarded Honorable Mention by Grav.Res.Found.,
199
Fermi Coordinates and Penrose Limits
We propose a formulation of the Penrose plane wave limit in terms of null
Fermi coordinates. This provides a physically intuitive (Fermi coordinates are
direct measures of geodesic distance in space-time) and manifestly covariant
description of the expansion around the plane wave metric in terms of
components of the curvature tensor of the original metric, and generalises the
covariant description of the lowest order Penrose limit metric itself, obtained
in hep-th/0312029. We describe in some detail the construction of null Fermi
coordinates and the corresponding expansion of the metric, and then study
various aspects of the higher order corrections to the Penrose limit. In
particular, we observe that in general the first-order corrected metric is such
that it admits a light-cone gauge description in string theory. We also
establish a formal analogue of the Weyl tensor peeling theorem for the Penrose
limit expansion in any dimension, and we give a simple derivation of the
leading (quadratic) corrections to the Penrose limit of AdS_5 x S^5.Comment: 25 page
Penrose Limits and Spacetime Singularities
We give a covariant characterisation of the Penrose plane wave limit: the
plane wave profile matrix is the restriction of the null geodesic
deviation matrix (curvature tensor) of the original spacetime metric to the
null geodesic, evaluated in a comoving frame. We also consider the Penrose
limits of spacetime singularities and show that for a large class of black
hole, cosmological and null singularities (of Szekeres-Iyer ``power-law
type''), including those of the FRW and Schwarzschild metrics, the result is a
singular homogeneous plane wave with profile , the scale
invariance of the latter reflecting the power-law behaviour of the
singularities.Comment: 9 pages, LaTeX2e; v2: additional references and cosmetic correction
On the pp-wave limit and the BMN structure of new Sasaki-Einstein spaces
We construct the pp-wave string associated with the Penrose limit of
and families of Sasaki-Einstein geometries. We identify
in the dual quiver gauge theories the chiral and the non-chiral operators that
correspond to the ground state and the first excited states. We present an
explicit identification in a prototype model of .Comment: 21 pages, JHEP format, 5 figures, acknowledgement correcte
On Penrose limit of elliptic branes
We discuss a Penrose limit of an elliptic brane configuration with NS5
and D4 branes. This background is T-dual to D3 branes at a fixed
point of a singularity and the T-duality
survives the Penrose limit. The triple scaling limit of and gives
rise to IIA pp-wave solution with a space-like compact direction. We identify
the quiver gauge theory operators and argue that upon exchange of the momentum
along the compact direction and the winding number these operators coincide
with the operators derived in the dual type IIB description. We also find a new
Penrose limit of the type IIB background and the corresponding limit in the
type IIA picture. In the coordinate system we use there are two manifest
space-like isometries. The quiver gauge theory operator duals of the string
states are built of three bosonic fields.Comment: 25 pages with 1 figur
Topological Aspects of Gauge Fixing Yang-Mills Theory on S4
For an space-time manifold global aspects of gauge-fixing are
investigated using the relation to Topological Quantum Field Theory on the
gauge group. The partition function of this TQFT is shown to compute the
regularized Euler character of a suitably defined space of gauge
transformations. Topological properties of the space of solutions to a
covariant gauge conditon on the orbit of a particular instanton are found using
the isometry group of the base manifold. We obtain that the Euler
character of this space differs from that of an orbit in the topologically
trivial sector. This result implies that an orbit with Pontryagin number
\k=\pm1 in covariant gauges on contributes to physical correlation
functions with a different multiplicity factor due to the Gribov copies, than
an orbit in the trivial \k=0 sector. Similar topological arguments show that
there is no contribution from the topologically trivial sector to physical
correlation functions in gauges defined by a nondegenerate background
connection. We discuss possible physical implications of the global gauge
dependence of Yang-Mills theory.Comment: 13 pages, uuencoded and compressed LaTeX file, no figure
Quantizing three-spin string solution in AdS_5 x S^5
As was recently found in hep-th/0304255, there exists a simple
non-supersymmetric classical solution describing a closed string rotating in
S^5 and located at the center of AdS_5. It is parametrized by the angular
momentum J of the center of mass and two equal SO(6) angular momenta J' in the
two other orthogonal rotation planes. The dual N=4 SYM operators should be
scalar operators in SU(4) representations [0,J-J',2J'] or [J'-J,0,J'+J]. This
solution is stable if J' > 3/2 J and for large J + 2 J' its classical energy
admits an expansion in positive powers of g_eff = \lambda/(J + 2 J')^2: E= J +
2 J' + g_eff J' + ... . This suggests a possibility of a direct comparison with
perturbative SYM results for the corresponding anomalous dimensions in the
sector with g_eff << 1, by analogy with the BMN case. We conjecture that all
quantum sigma model string corrections are then subleading at large J', so that
the classical formula for the energy is effectively exact to all orders in
\lambda. It could then be interpolated to weak coupling, representing a
prediction for the anomalous dimensions on the SYM side. We test this
conjecture by computing the 1-loop superstring sigma model correction to the
classical energy.Comment: 25 pages, harvmac. v5: minor misprints in eqs
(2.6),(2.16),(2.20),(2.21) correcte
Conformal Field Theory for the Superstring in a Ramond-Ramond Plane Wave Background
A quantizable worldsheet action is constructed for the superstring in a
supersymmetric plane wave background with Ramond-Ramond flux. The action is
manifestly invariant under all isometries of the background and is an exact
worldsheet conformal field theory.Comment: 13 pages harvma
Dissipative Hydrodynamics and Heavy Ion Collisions
Recent discussions of RHIC data emphasized the exciting possibility that the
matter produced in nucleus-nucleus collisions shows properties of a
near-perfect fluid. Here, we aim at delineating the applicability of fluid
dynamics, which is needed to quantify the size of corresponding dissipative
effects. We start from the equations for dissipative fluid dynamics, which we
derive from kinetic theory up to second order (Israel-Stewart theory) in a
systematic gradient expansion. In model studies, we then establish that for too
early initialization of the hydrodynamic evolution (\tau_0 \lsim 1 fm/c) or
for too high transverse momentum (p_T \gsim 1 GeV) in the final state, the
expected dissipative corrections are too large for a fluid description to be
reliable. Moreover, viscosity-induced modifications of hadronic transverse
momentum spectra can be accommodated to a significant degree in an ideal fluid
description by modifications of the decoupling stage. We argue that these
conclusions, drawn from model studies, can also be expected to arise in
significantly more complex, realistic fluid dynamics simulations of heavy ion
collisions.Comment: 18 pages, 5 figures, uses revtex4; v2: references added, typos
correcte
Semiclassical quantization of rotating superstring in AdS_5 x S^5
Motivated by recent proposals in hep-th/0202021 and hep-th/0204051 we develop
semiclassical quantization of superstring in . We start with a
classical solution describing string rotating in and boosted along
large circle of . The energy of the classical solution is a function
of the spin and the momentum (R-charge) which interpolates between the
limiting cases S=0 and J=0 considered previously. We derive the corresponding
quadratic fluctuation action for bosonic and fermionic fields from the GS
string action and compute the string 1-loop (large \lambda= {R^4\over \a'^2})
correction to the classical energy spectrum in the sector. We find that
the 1-loop correction to the ground-state energy does not cancel for non-zero
. For large it scales as , i.e. as the classical term, with no
higher powers of appearing. This supports the conjecture made in
hep-th/0204051 that the classical scaling can be interpolated
to weak coupling to reproduce the corresponding operator anomalous dimension
behaviour in gauge theory.Comment: harvmac, 35p. v2,3: minor corrections; v4: added remarks about
higher-loop corrections in section 4 and an argument suggesting the absence
of higher than log S corrections to the energy to all orders in string
tension in section 6.1; v5: factor 1/2 misprints corrected in eqs. (6.6) and
(6.8) and thus in (6.5) and (6.9
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