132 research outputs found
Stringy effects for spinning strings and the Bethe ansatz
The one-loop worldsheet corrections to spinning strings in the sl(2) subsector of AdS5 Ă— S5 are compared to the quantum string Bethe ansatz. The evaluation of the energy shift is performed in two regimes: a) in the large limit, using zeta-function regularization and b) in the limit of large winding number. The first computation agrees with the Bethe ansatz in the first three orders while the second computation leads to a disagreement with the string Bethe ansatz prediction at leading order. Careful analysis of the zeta-function regularization shows, that in this approach perturbative as well as non-perturbative terms in the string sums are missed. Hence, this together with the result b), implies that the proposed quantum string Bethe equations do not reproduce all terms in the exact string result
On AdS_5 x S^5 String S-matrix
Recently two interesting conjectures about the string S-matrix on AdS_5 x S^5
have been made. First, assuming the existence of a Hopf algebra symmetry Janik
derived a functional equation for the dressing factor of the quantum string
Bethe ansatz. Second, Hernandez and Lopez proposed an explicit form of
1/\sqrt\lambda correction to the dressing factor. In this note we show that in
the strong coupling expansion Janik's equation is solved by the dressing factor
up to the order of its validity. This observation provides a strong evidence in
favor of a conjectured Hopf algebra symmetry for strings in AdS_5 x S^5 as well
as the perturbative string S-matrix.Comment: 10 pages, version2: misprints are correcte
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 the Scattering Phase for AdS_5 x S^5 Strings
We propose a phase factor of the worldsheet S-matrix for strings on AdS_5 x
S^5 apparently solving Janik's crossing relation.Comment: 9 pages, v2: revised conclusions about agreement with perturbative
string theory; minor changes, v3: resolution to above problems indicated, to
appear in Mod. Phys. Lett.
Decays of metastable vacua in SQCD
The decay rates of metastable SQCD vacua in ISS-type models, both towards
supersymmetric vacua as well as towards other nonsupersymmetric configurations
arising in theories with elementary spectators, are estimated numerically in
the semiclassical approximation by computing the corresponding multifield
bounce configurations. The scaling of the bounce action with respect to the
most relevant dimensionless couplings and ratios of scales is analyzed. In the
case of the decays towards the susy vacua generated by nonperturbative effects,
the results confirm previous analytical estimations of this scaling, obtained
by assuming a triangular potential barrier. The decay rates towards susy vacua
generated by R-symmetry breaking interactions turn out to be more than
sufficiently suppressed for the phenomenologically relevant parameter range,
and their behavior in this regime differs from analytic estimations valid for
parametrically small scale ratios. It is also shown that in models with
spectator fields, even though the decays towards vacua involving nonzero
spectator VEVs don't have a strong parametric dependence on the scale ratios,
the ISS vacuum can still be made long-lived in the presence of R-symmetry
breaking interactions.Comment: 22 pages, 7 figure
Twisted K-Theory of Lie Groups
I determine the twisted K-theory of all compact simply connected simple Lie
groups. The computation reduces via the Freed-Hopkins-Teleman theorem to the
CFT prescription, and thus explains why it gives the correct result. Finally I
analyze the exceptions noted by Bouwknegt et al.Comment: 16 page
A microscopic theory of gauge mediation
We construct models of indirect gauge mediation where the dynamics
responsible for breaking supersymmetry simultaneously generates a weakly
coupled subsector of messengers. This provides a microscopic realization of
messenger gauge mediation where the messenger and hidden sector fields are
unified into a single sector. The UV theory is SQCD with massless and massive
quarks plus singlets, and at low energies it flows to a weakly coupled quiver
gauge theory. One node provides the primary source of supersymmetry breaking,
which is then transmitted to the node giving rise to the messenger fields.
These models break R-symmetry spontaneously, produce realistic gaugino and
sfermion masses, and give a heavy gravitino.Comment: 24 pages, 2 figures, accepted to JHEP for publicatio
G-flux and Spectral Divisors
We propose a construction of G-flux in singular elliptic Calabi-Yau fourfold
compactifications of F-theory, which in the local limit allow a spectral cover
description. The main tool of construction is the so-called spectral divisor in
the resolved Calabi-Yau geometry, which in the local limit reduces to the Higgs
bundle spectral cover. We exemplify the workings of this in the case of an E_6
singularity by constructing the resolved geometry, the spectral divisor and in
the local limit, the spectral cover. The G-flux constructed with the spectral
divisor is shown to be equivalent to the direct construction from suitably
quantized linear combinations of holomorphic surfaces in the resolved geometry,
and in the local limit reduces to the spectral cover flux.Comment: 30 page
Coset Construction for Duals of Non-relativistic CFTs
We systematically analyze backgrounds that are holographic duals to
non-relativistic CFTs, by constructing them as cosets of the Schrodinger group
and variants thereof. These cosets G/H are generically non-reductive and we
discuss in generality how a metric on such spaces can be determined from a
non-degenerate H-invariant symmetric two-form. Applying this to the d=2
Schrodinger algebra, we reproduce the five-dimensional backgrounds proposed as
duals of fermions at unitarity, and under reasonable physical assumptions, we
demonstrate uniqueness of this background. The proposed gravity dual of the
Lifshitz fixed-point, for which Galileian symmetry is absent, also fits into
this organizational scheme and uniqueness of this background can also be shown.Comment: 12 pages; v2: typos corrected, references adde
UV finiteness of Pohlmeyer-reduced form of the AdS_5xS^5 superstring theory
We consider the Pohlmeyer-type reduced theory found by explicitly solving the
Virasoro constraints in the formulation of AdS_5xS^5 superstring in terms of
supercoset currents. The resulting set of classically equivalent, integrable
Lagrangian equations of motion has the advantage of involving only a physical
number of degrees of freedom and yet being 2d Lorentz invariant. The
corresponding reduced theory action may be written as a gauged WZW model
coupled to fermions with further bosonic and fermionic potential terms. Since
the AdS_5xS^5 superstring sigma model is conformally invariant, its classical
relation to the reduced theory may extend to the quantum level only if the
latter is, in fact, UV finite. This theory is power counting renormalizable
with the only possible divergences being of potential type. We explicitly
verify its 1-loop finiteness and show that the 2-loop divergences are, in
general, scheme dependent and vanish in dimensional reduction scheme. We expect
that the reduced theory is finite to all orders in the loop expansion.Comment: 40 pages, Latex; v2: typos corrected, minor clarifying remarks adde
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