1,174 research outputs found
Spiky strings, light-like Wilson loops and pp-wave anomaly
We consider rigid rotating closed strings with spikes in AdS5 dual to certain
higher twist operators in N=4 SYM theory. In the limit of large spin when the
spikes reach the boundary of AdS5, the solutions with different numbers of
spikes are related by conformal transformations, implying that their energy is
determined by the same function of the `t Hooft coupling f(lambda) that appears
in the anomalous dimension of twist 2 operators or in the cusp anomaly. In the
limit when the number of spikes goes to infinity, we find an equivalent
description in terms of a string moving in an AdS pp-wave background. From the
boundary theory point of view, the corresponding description is based on the
gauge theory living in a 4d pp-wave space. Then, considering a charge moving at
the speed of light, or a null Wilson line, we find that the integrated energy
momentum tensor has a logarithmic UV divergence whose coefficient we call the
"pp-wave anomaly". The AdS/CFT correspondence implies that, for N=4 SYM, this
pp-wave anomaly should have the same value as the cusp anomaly. We verify this
at lowest order in SYM perturbation theory. As a side result of our string
theory analysis, we find new open string solutions in the Poincare patch of the
standard AdS space which end on a light-like Wilson line and also in two
parallel light-like Wilson lines at the boundary.Comment: 28 pages, 2 eps figures, LaTeX. v2: typos correcte
Higher spins in AdS_5 at one loop: vacuum energy, boundary conformal anomalies and AdS/CFT
We consider general-symmetry higher spin fields in AdS_5 and derive
expressions for their one-loop corrections to vacuum energy E and the
associated 4d boundary conformal anomaly a-coefficient. We a propose a similar
expression for the second conformal anomaly c-coefficient. We show that all the
three quantities (E, a, c) computed for N=8 gauged 5d supergravity are -1/2 of
the values for N=4 conformal 4d supergravity and also twice the values for N=4
Maxwell multiplet. This gives 5d derivation of the fact that the system of N=4
conformal supergravity and four N=4 Maxwell multiplets is anomaly free. The
values of (E, a, c) for the states at level p of Kaluza-Klein tower of 10d type
IIB supergravity compactified on S^5 turn out to be equal to those for p copies
of N=4 Maxwell multiplets. This may be related to the fact that these states
appear in the tensor product of p superdoubletons. Under a natural
regularization of the sum over p, the full 10d supergravity contribution is
then minus that of the Maxwell multiplet, in agreement with the standard
adjoint AdS/CFT duality (SU(n) SYM contribution is n^2-1 of one Maxwell
multiplet). We also verify the matching of (E, a, c) for spin 0 and 1/2
boundary theory cases of vectorial AdS/CFT duality. The consistency conditions
for vectorial AdS/CFT turn out to be equivalent to the cancellation of
anomalies in the closely related 4d conformal higher spin theories. In
addition, we study novel example of vectorial AdS/CFT duality when the boundary
theory is described by free spin 1 fields and is dual to a particular higher
spin theory in AdS_5 containing fields in mixed-symmetry representations. We
also discuss its supersymmetric generalizations.Comment: 56 pages. v2,v3: minor corrections, references adde
Pohlmeyer reduction of AdS_5 x S^5 superstring sigma model
Motivated by a desire to find a useful 2d Lorentz-invariant reformulation of
the AdS_5 x S^5 superstring world-sheet theory in terms of physical degrees of
freedom we construct the Pohlmeyer-reduced version of the corresponding sigma
model. The Pohlmeyer reduction procedure involves several steps. Starting with
a coset space string sigma model in the conformal gauge and writing the
classical equations in terms of currents one can fix the residual conformal
diffeomorphism symmetry and kappa-symmetry and introduce a new set of variables
(related locally to currents but non-locally to the original string coordinate
fields) so that the Virasoro constraints are automatically satisfied. The
resulting gauge-fixed equations can be obtained from a Lagrangian of a
non-abelian Toda type: a gauged WZW model with an integrable potential coupled
also to a set of 2d fermionic fields. A gauge-fixed form of the
Pohlmeyer-reduced theory can be found by integrating out the 2d gauge field of
the gauged WZW model. Its small-fluctuation spectrum contains 8 bosonic and 8
fermionic degrees of freedom with equal masses. We conjecture that the reduced
model has world-sheet supersymmetry and is ultraviolet-finite. We show that in
the special case of the AdS_2 x S^2 superstring model the reduced theory is
indeed supersymmetric: it is equivalent to the N=2 supersymmetric extension of
the sine-Gordon model.Comment: 56 pages. v2: section 6.4 expanded with comments on mass spectrum and
the corresponding S-matrix; v3,v4: minor corrections and clarifications adde
On conformal higher spins in curved background
We address the question of how to represent an interacting action for the
tower of conformal higher spin fields in a form covariant with respect to a
background metric. We use a background metric to define a star product which
plays a central role in the definition of the corresponding gauge
transformations. By an analogy with the kinetic term in the 4-derivative Weyl
gravity action expanded near an on-shell background one expects that the
kinetic term in such an action should be gauge-invariant in a Bach-flat metric.
We demonstrate this fact to first order in expansion in powers of the curvature
of the background metric. This generalizes the result of arXiv:1404.7452 for
spin 3 case to all conformal higher spins. We also comment on a possibility of
extending this claim to terms quadratic in the curvature and discuss the
appearance of background-dependent mixing terms in the quadratic part of the
conformal higher spin action.Comment: 24 pages. v2,v3: minor corrections and remarks adde
Non-extreme black holes from non-extreme intersecting M-branes
We present non-extreme generalisations of intersecting p-brane solutions of
eleven-dimensional supergravity which upon toroidal compactification reduce to
non-extreme static black holes in dimensions D=4, D=5 and 5<D<10, parameterized
by four, three and two charges, respectively. The D=4 black holes are obtained
either from non-extreme configuration of three intersecting five-branes with a
boost along the common string or from non-extreme intersecting system of two
two-branes and two five-branes. The D=5 black holes arise from three
intersecting two-branes or from a system of intersecting two-brane and
five-brane with a boost along the common string. Five-brane and two-brane with
a boost along one direction reduce to black holes in D=6 and D=9, respectively,
while D=7 black hole can be interpreted in terms of non-extreme configuration
of two intersecting two-branes. We discuss the expressions for the
corresponding masses and entropies.Comment: 19 pages, latex (misprints corrected; remarks added in section 6
On higher spin partition functions
We observe that the partition function of the set of all free massless higher
spins s=0,1,2,3,... in flat space is equal to one: the ghost determinants
cancel against the "physical" ones or, equivalently, the (regularized) total
number of degrees of freedom vanishes. This reflects large underlying gauge
symmetry and suggests analogy with supersymmetric or topological theory. The
Z=1 property extends also to the AdS background, i.e. the 1-loop vacuum
partition function of Vasiliev theory is equal to 1 (assuming a particular
regularization of the sum over spins); this was noticed earlier as a
consistency requirement for the vectorial AdS/CFT duality. We find that Z=1 is
also true in the conformal higher spin theory (with higher-derivative d^{2s}
kinetic terms) expanded near flat or conformally flat S^4 background. We also
consider the partition function of free conformal theory of symmetric traceless
rank s tensor field which has 2-derivative kinetic term but only scalar gauge
invariance in flat 4d space. This non-unitary theory has a Weyl-invariant
action in curved background and corresponds to "partially massless" field in
AdS_5. We discuss in detail the special case of s=2 (or "conformal graviton"),
compute the corresponding conformal anomaly coefficients and compare them with
previously found expressions for generic representations of conformal group in
4 dimensions.Comment: 35 pages. v3: minor clarifications, comments, and references adde
Conformal a-anomaly of some non-unitary 6d superconformal theories
We compute the conformal anomaly a-coefficient for some non-unitary (higher
derivative or non-gauge-invariant) 6d conformal fields and their
supermultiplets. We use the method based on a connection between 6d
determinants on S^6 and 7d determinants on AdS_7. We find, in particular, that
(1,0) supermultiplet containing 4-derivative gauge-invariant conformal vector
has precisely the value of a-anomaly as attributed in arXiv:1506.03807 (on the
basis of R-symmetry and gravitational 't Hooft matching) to the standard (1,0)
vector multiplet. We also show that higher derivative (2,0) 6d conformal
supergravity coupled to exactly 26 (2,0) tensor multiplets has vanishing
a-anomaly. This is the 6d counterpart of the known fact of cancellation of the
conformal anomaly in the 4d system of N=4 conformal supergravity coupled to 4
vector N=4 multiplets. In the case when 5 of tensor multiplets are chosen to be
ghost-like and the conformal symmetry is spontaneously broken by a quadratic
scalar constraint the resulting IR theory may be identified with (2,0) Poincare
supergravity coupled to 21=26-5 tensor multiplets. The latter theory is known
to be special: it is gravitational anomaly free and results upon
compactification of 10d type IIB supergravity on K3.Comment: 22 pages. v3: minor comments and references added, appendix expanded;
v4: minor correction
Higher Order Graviton Scattering in M(atrix) Theory
In matrix theory the effective action for graviton-graviton scattering is a
double expansion in the relative velocity and inverse separation. We discuss
the systematics of this expansion and subject matrix theory to a new test. Low
energy supergravity predicts the coefficient of the term, a
two-loop effect, in agreement with explicit matrix model calculation.Comment: 15 pages, 1 epsf figure, LaTeX. Minor change
Radio emission of sea surface at centimeter wavelengths and is fluctuations
The eigen thermal radio emission of the sea was examined as well as the agitated surface of the sea when the reflection (scattering) is similar in nature to diffused scattering. The contribution of this emission to the total emission of the sea is practically constant in time, and the time fluctuations of the radio emissions of the sea are basically determined only by a change in the eigen emission of the sea, connected with the agitation
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