24 research outputs found
Higher spins on AdS from the worldsheet
It was recently shown that the CFT dual of string theory on , the symmetric orbifold of , contains a
closed higher spin subsector. Via holography, this makes precise the sense in
which tensionless string theory on this background contains a Vasiliev higher
spin theory. In this paper we study this phenomenon directly from the
worldsheet. Using the WZW description of the background with pure NS-NS flux,
we identify the states that make up the leading Regge trajectory and show that
they fit into the even spin Vasiliev higher spin theory. We also
show that these higher spin states do not become massless, except for the
somewhat singular case of level where the theory contains a stringy tower
of massless higher spin fields coming from the long string sector.Comment: 29+8 pages, 3 figure
Observables and Microscopic Entropy of Higher Spin Black Holes
In the context of recently proposed holographic dualities between higher spin
theories in AdS3 and 1+1-dimensional CFTs with W-symmetry algebras, we revisit
the definition of higher spin black hole thermodynamics and the dictionary
between bulk fields and dual CFT operators. We build a canonical formalism
based on three ingredients: a gauge-invariant definition of conserved charges
and chemical potentials in the presence of higher spin black holes, a canonical
definition of entropy in the bulk, and a bulk-to-boundary dictionary aligned
with the asymptotic symmetry algebra. We show that our canonical formalism
shares the same formal structure as the so-called holomorphic formalism, but
differs in the definition of charges and chemical potentials and in the
bulk-to-boundary dictionary. Most importantly, we show that it admits a
consistent CFT interpretation. We discuss the spin-2 and spin-3 cases in detail
and generalize our construction to theories based on the hs[\lambda] algebra,
and on the sl(N,R) algebra for any choice of sl(2,R) embedding.Comment: 47 pages, references added, published versio
Higher Spin Entanglement and W_N Conformal Blocks
Two-dimensional conformal field theories with extended -symmetry
algebras have dual descriptions in terms of weakly coupled higher spin gravity
in AdS at large central charge. Observables that can be computed and
compared in the two descriptions include R\'enyi and entanglement entropies,
and correlation functions of local operators. We develop techniques for
computing these, in a manner that sheds light on when and why one can expect
agreement between such quantities on each side of the duality. We set up the
computation of excited state R\'enyi entropies in the bulk in terms of
Chern-Simons connections, and show how this directly parallels the CFT
computation of correlation functions. More generally, we consider the vacuum
conformal block for general operators with . When two of the
operators obey , we show by explicit computation that
the vacuum conformal block is computed by a bulk Wilson line probing an
asymptotically AdS background with higher spin fields excited, the latter
emerging as the effective bulk description of the excited state produced by the
heavy operators. Among other things, this puts a previous proposal for
computing higher spin entanglement entropy via Wilson lines on firmer footing,
and clarifies its relation to CFT. We also study the corresponding computation
in Toda theory and find that this provides yet another independent way to
arrive at the same result.Comment: 56 page
Pion form factor in the Kroll-Lee-Zumino model
The renormalizable Abelian quantum field theory model of Kroll, Lee, and
Zumino is used to compute the one-loop vertex corrections to the tree-level,
Vector Meson Dominance (VMD) pion form factor. These corrections, together with
the known one-loop vacuum polarization contribution, lead to a substantial
improvement over VMD. The resulting pion form factor in the space-like region
is in excellent agreement with data in the whole range of accessible momentum
transfers. The time-like form factor, known to reproduce the Gounaris-Sakurai
formula at and near the rho-meson peak, is unaffected by the vertex correction
at order (g_\rpp^2).Comment: Revised version corrects a misprint in Eq.(1
Aging and Holography
Aging phenomena are examples of `non-equilibrium criticality' and can be
exemplified by systems with Galilean and scaling symmetries but no time
translation invariance. We realize aging holographically using a deformation of
a non-relativistic version of gauge/gravity duality. Correlation functions of
scalar operators are computed using holographic real-time techniques, and agree
with field theory expectations. At least in this setup, general aging phenomena
are reproduced holographically by complexifying the bulk space-time geometry,
even in Lorentzian signature.Comment: 1 pdf figur
Thermodynamics of Higher Spin Black Holes in AdS
We discuss the thermodynamics of recently constructed three-dimensional
higher spin black holes in SL(N,R)\times SL(N,R) Chern-Simons theory with
generalized asymptotically-anti-de Sitter boundary conditions. From a
holographic perspective, these bulk theories are dual to two-dimensional CFTs
with W_N symmetry algebras, and the black hole solutions are dual to thermal
states with higher spin chemical potentials and charges turned on. Because the
notion of horizon area is not gauge-invariant in the higher spin theory, the
traditional approaches to the computation of black hole entropy must be
reconsidered. One possibility, explored in the recent literature, involves
demanding the existence of a partition function in the CFT, and consistency
with the first law of thermodynamics. This approach is not free from
ambiguities, however, and in particular different definitions of energy result
in different expressions for the entropy. In the present work we show that
there are natural definitions of the thermodynamically conjugate variables that
follow from careful examination of the variational principle, and moreover
agree with those obtained via canonical methods. Building on this intuition, we
derive general expressions for the higher spin black hole entropy and free
energy which are written entirely in terms of the Chern-Simons connections, and
are valid for both static and rotating solutions. We compare our results to
other proposals in the literature, and provide a new and efficient way to
determine the generalization of the Cardy formula to a situation with higher
spin charges.Comment: 30 pages, PDFLaTeX; v2: typos corrected, explicit expressions for the
free energy adde
Fermions and Type IIB Supergravity On Squashed Sasaki-Einstein Manifolds
We discuss the dimensional reduction of fermionic modes in a recently found
class of consistent truncations of type IIB supergravity compactified on
squashed five-dimensional Sasaki-Einstein manifolds. We derive the lower
dimensional equations of motion and effective action, and comment on the
supersymmetry of the resulting theory, which is consistent with N=4 gauged
supergravity in , coupled to two vector multiplets. We compute fermion
masses by linearizing around two vacua of the theory: one that breaks
N=4 down to N=2 spontaneously, and a second one which preserves no
supersymmetries. The truncations under consideration are noteworthy in that
they retain massive modes which are charged under a U(1) subgroup of the
-symmetry, a feature that makes them interesting for applications to
condensed matter phenomena via gauge/gravity duality. In this light, as an
application of our general results we exhibit the coupling of the fermions to
the type IIB holographic superconductor, and find a consistent further
truncation of the fermion sector that retains a single spin-1/2 mode.Comment: 43 pages, 2 figures, PDFLaTeX; v2: added references, typos corrected,
minor change