135 research outputs found
Quantum corrections to the string Bethe ansatz
One-loop corrections to the energy of semiclassical rotating strings contain
both analytic and non-analytic terms in the 't Hooft coupling. Analytic
contributions agree with the prediction from the string Bethe ansatz based on
the classical S-matrix, but in order to include non-analytic contributions
quantum corrections are required. We find a general expression for the first
quantum correction to the string Bethe ansatz.Comment: 12 pages. Latex. v2: Misprints corrected and references adde
On String S-matrix, Bound States and TBA
The study of finite J effects for the light-cone AdS superstring by means of
the Thermodynamic Bethe Ansatz requires an understanding of a companion 2d
theory which we call the mirror model. It is obtained from the original string
model by the double Wick rotation. The S-matrices describing the scattering of
physical excitations in the string and mirror models are related to each other
by an analytic continuation. We show that the unitarity requirement for the
mirror S-matrix fixes the S-matrices of both theories essentially uniquely. The
resulting string S-matrix S(z_1,z_2) satisfies the generalized unitarity
condition and, up to a scalar factor, is a meromorphic function on the elliptic
curve associated to each variable z. The double Wick rotation is then
accomplished by shifting the variables z by quarter of the imaginary period of
the torus. We discuss the apparent bound states of the string and mirror
models, and show that depending on a choice of the physical region there are
one, two or 2^{M-1} solutions of the M-particle bound state equations sharing
the same conserved charges. For very large but finite values of J, most of
these solutions, however, exhibit various signs of pathological behavior. In
particular, they might receive a finite J correction to their energy which is
complex, or the energy correction might exceed corrections arising due to
finite J modifications of the Bethe equations thus making the asymptotic Bethe
ansatz inapplicable.Comment: 77 pages, 6 figures, v2: the statement about the periodicity
condition for mirror fermions corrected; typos corrected; references added,
v3: misprints correcte
The origin of the anomalously strong influence of out-of-plane disorder on high-Tc superconductivity
The electronic structure of Bi2Sr2-xRxCuOy(R=La, Eu) near the (pi,0) point of
the first Brillouin zone was studied by means of angle-resolved photoemission
spectroscopy (ARPES). The temperature T* above which the pseudogap structure in
the ARPES spectrum disappears was found to have an R dependence that is
opposite to that ofthe superconducting transition temperature Tc. This
indicates that the pseudogap state is competing with high-Tc superconductivity,
and the large Tc suppression observed with increasing the out-of-plane disorder
is due to the stabilization of the pseudogap state.Comment: 4 pages, 4 figure
Compact F-theory GUTs with U(1)_PQ
We construct semi-local and global realizations of SU(5) GUTs in F-theory
that utilize a U(1)_PQ symmetry to protect against dimension four proton decay.
Symmetries of this type, which assign charges to H_u and H_d that forbid a tree
level \mu term, play an important role in scenarios for neutrino physics and
gauge mediation that have been proposed in local F-theory model building. As
demonstrated in arXiv:0906.4672, the presence of such a symmetry implies the
existence of non-GUT exotics in the spectrum, when hypercharge flux is used to
break the GUT group and to give rise to doublet-triplet splitting. These
exotics are of precisely the right type to solve the unification problem in
such F-theory models and might also comprise a non-standard messenger sector
for gauge mediation. We present a detailed description of models with U(1)_PQ
in the semi-local regime, which does not depend on details of any specific
Calabi-Yau four-fold, and then specialize to the geometry of arXiv:0904.3932 to
construct three-generation examples with the minimal allowed number of non-GUT
exotics. Among these, we find a handful of models in which the D3-tadpole
constraint can be satisfied without requiring the introduction of
anti-D3-branes. Finally, because SU(5) singlets that carry U(1)_PQ charge may
serve as candidate right-handed neutrinos or can be used to lift the exotics,
we study their origin in compact models and motivate a conjecture for how to
count their zero modes in a semi-local setting.Comment: 73 pages, 5 figures, v2: minor corrections to 4.3 and 6.3.1,
reference adde
Higher Loop Bethe Ansatz for Open Spin-Chains in AdS/CFT
We propose a perturbative asymptotic Bethe ansatz (PABA) for open spin-chain
systems whose Hamiltonians are given by matrices of anomalous dimension for
composite operators, and apply it to two types of composite operators related
to two different brane configurations. One is an AdS_4 \times S^2-brane in the
bulk AdS_5 \times S^5 which gives rise to a defect conformal field theory
(dCFT) in the dual field theory, and the other is a giant graviton system with
an open string excitation. In both cases, excitations on open strings attaching
to D-branes (a D5-brane for the dCFT case, and a spherical D3-brane for the
giant graviton case) can be represented by magnon states in the spin-chains
with appropriate boundary conditions, in which informations of the D-branes are
encoded. We concentrate on single-magnon problems, and explain how to calculate
boundary S-matrices via the PABA technique. We also discuss the energy spectrum
in the BMN limit.Comment: 1+24 pages, 1 figure, typos corrected, references added, discussions
on the integrability for giant gravitons modified, version to appear in JHE
Semiclassical Strings, Dipole Deformations of N=1 SYM and Decoupling of KK Modes
In this paper we investigate the recently found -deformed
Maldacena-Nunez background by studying the behavior of different semiclassical
string configurations. This background is conjectured to be dual to dipole
deformations of SYM. We compare our results to those in the pure
Maldacena-Nunez background and show that the energies of our string
configurations are higher than in the undeformed background. Thinking in the
lines of (hep-th/0505100) we argue that this is an evidence for better
decoupling of the Kaluza-Klein modes from the pure SYM theory excitations.
Moreover we are able to find a limit of the background in which the string
energy is independent of , these strings are interpreted as
corresponding to pure gauge theory effects.Comment: 31 pages, references added, new solutions in Section 7 presented, an
appendix added, to appear in JHE
Integrable twists in AdS/CFT
A class of marginal deformations of four-dimensional N=4 super Yang-Mills
theory has been found to correspond to a set of smooth, multiparameter
deformations of the S^5 target subspace in the holographic dual on AdS_5 x S^5.
We present here an analogous set of deformations that act on global toroidal
isometries in the AdS_5 subspace. Remarkably, certain sectors of the string
theory remain classically integrable in this larger class of so-called
gamma-deformed AdS_5 x S^5 backgrounds. Relying on studies of deformed
su(2)_gamma models, we formulate a local sl(2)_gamma Lax representation that
admits a classical, thermodynamic Bethe equation (based on the Riemann-Hilbert
interpretation of Bethe's ansatz) encoding the spectrum in the deformed AdS_5
geometry. This result is extended to a set of discretized, asymptotic Bethe
equations for the twisted string theory. Near-pp-wave energy spectra within
sl(2)_gamma and su(2)_gamma sectors provide a useful and stringent test of such
equations, demonstrating the reliability of this technology in a wider class of
string backgrounds. In addition, we study a twisted Hubbard model that yields
certain predictions of the dual beta-deformed gauge theory.Comment: v2: references and clarifications added, 46 page
Integrable Spin Chains on the Conformal Moose
We consider N=1, D=4 superconformal U(N)^{pq} Yang-Mills theories dual to
AdS_5xS^5/Z_pxZ_q orbifolds. We construct the dilatation operator of this
superconformal gauge theory at one-loop planar level. We demonstrate that a
specific sector of this dilatation operator can be thought of as the transfer
matrix for a two-dimensional statistical mechanical system, related to an
integrable SU(3) anti-ferromagnetic spin chain system, which in turn is
equivalent to a 2+1-dimensional string theory where the spatial slices are
discretized on a triangular lattice. This is an extension of the SO(6) spin
chain picture of N=4 super Yang-Mills theory. We comment on the integrability
of this N=1 gauge theory and hence the corresponding three-dimensional
statistical mechanical system, its connection to three-dimensional lattice
gauge theories, extensions to six-dimensional string theories, AdS/CFT type
dualities and finally their construction via orbifolds and brane-box models. In
the process we discover a new class of almost-BPS BMN type operators with large
engineering dimensions but controllably small anomalous corrections.Comment: 53 pages, 14 eps figures; Added reference
Green-Schwarz Strings in TsT-transformed backgrounds
We consider classical strings propagating in a background generated by a
sequence of TsT transformations. We describe a general procedure to derive the
Green-Schwarz action for strings. We show that the U(1) isometry variables of
the TsT-transformed background are related to the isometry variables of the
initial background in a universal way independent of the details of the
background. This allows us to prove that strings in the TsT-transformed
background are described by the Green-Schwarz action for strings in the initial
background subject to twisted boundary conditions. Our construction implies
that a TsT transformation preserves integrability properties of the string
sigma model. We discuss in detail type IIB strings propagating in the
\g_i-deformed AdS_5 x S^5 space-time, find the twisted boundary conditions for
bosons and fermions, and use them to write down an explicit expression for the
monodromy matrix. We also discuss string zero modes whose dynamics is governed
by a fermionicgeneralization of the integrable Neumann model.Comment: 33 pages, latex, v2: typos correcte
A new derivation of Luscher F-term and fluctuations around the giant magnon
15 pages, no figures; v2: added assumption on diagonal scattering and a section on generalizations; v3: minor changes, version accepted for publication in JHEPIn this paper we give a new derivation of the generalized Luscher F-term formula from a summation over quadratic fluctuations around a given soliton. The result is very general providing that S-matrix is diagonal and is valid for arbitrary dispersion relation. We then apply this formalism to compute the leading finite size corrections to the giant magnon dispersion relation coming from quantum fluctuations.Peer reviewe
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