170 research outputs found
Strings in a 2-d Extremal Black Hole
String theory on 2-d charged black holes corresponding to (SL(2)xU(1)_L)/U(1)
exact asymmetric quotient CFTs are investigated. These backgrounds can be
embedded, in particular, in a two dimensional heterotic string. In the extremal
case, the quotient CFT description captures the near horizon physics, and is
equivalent to strings in AdS_2 with a gauge field. Such string vacua possess an
infinite space-time Virasoro symmetry, and hence enhancement of global
space-time Lie symmetries to affine symmetries, in agreement with the
conjectured AdS_2/CFT_1 correspondence. We argue that the entropy of these 2-d
black holes in string theory is compatible with semi-classical results, and
show that in perturbative computations part of an incoming flux is absorbed by
the black hole. Moreover, on the way we find evidence that the 2-d heterotic
string is closely related to the N=(2,1) string, and conjecture that they are
dual.Comment: 1+22 pages, harvmac, 1 eps figure; v2: refs. added, typo correcte
The Holographic Fishchain
We present the first-principle derivation of a weak-strong duality between
the fishnet theory in four dimensions and a discretized string-like model
living in five dimensions. At strong coupling, the dual description becomes
classical and we demonstrate explicitly the classical integrability of the
model. We test our results by reproducing the strong coupling limit of the
-point correlator computed before non-perturbatively from the conformal
partial wave expansion. Due to the extreme simplicity of our model, it could
provide an ideal playground for holography with no super-symmetry. Furthermore,
since the fishnet model and SYM theory are continuously linked our
consideration could shed light on the derivation of AdS/CFT for the latter.Comment: 5 pages. v2: references added, v3 - acknowledgment adde
Large Gauge Symmetries and Asymptotic States in QED
Large Gauge Transformations (LGT) are gauge transformations that do not
vanish at infinity. Instead, they asymptotically approach arbitrary functions
on the conformal sphere at infinity. Recently, it was argued that the LGT
should be treated as an infinite set of global symmetries which are
spontaneously broken by the vacuum. It was established that in QED, the Ward
identities of their induced symmetries are equivalent to the Soft Photon
Theorem. In this paper we study the implications of LGT on the S-matrix between
physical asymptotic states in massive QED. In appose to the naively free
scattering states, physical asymptotic states incorporate the long range
electric field between asymptotic charged particles and were already
constructed in 1970 by Kulish and Faddeev. We find that the LGT charge is
independent of the particles' momenta and may be associated to the vacuum. The
soft theorem's manifestation as a Ward identity turns out to be an outcome of
not working with the physical asymptotic states.Comment: 22 pages, 3 figures, v2: major revisio
Planar scattering amplitudes from Wilson loops
We derive an expression for parton scattering amplitudes of planar gauge
theory in terms of sums of Wilson loops. We study in detail the example of
Yang-Mills theory with an adjoint Higgs field. The expression exhibits the
T-duality performed by Alday and Maldacena in the AdS dual as a Fourier
transform in loop space. When combined with the AdS/CFT correspondence for
Wilson loops and a strong coupling argument for the dominance of 1PI diagrams,
this leads to a derivation of the Alday-Maldacena holographic prescription for
scattering amplitudes in terms of momentum Wilson loops. The formula leads to a
conjecture for a relationship between position-space and momentum-space Wilson
loops in N=4 SYM at finite coupling.Comment: 30 + 16 pages, 9 figures. v2: corrected section
On Fine Structure of Strings: The Universal Correction to the Veneziano Amplitude
We consider theories of weakly interacting higher spin particles in flat
spacetime. We focus on the four-point scattering amplitude at high energies and
imaginary scattering angles. The leading asymptotic of the amplitude in this
regime is universal and equal to the corresponding limit of the Veneziano
amplitude. In this paper, we find that the first sub-leading correction to this
asymptotic is universal as well. We compute the correction using a model of
relativistic strings with massive endpoints. We argue that it is unique using
holography, effective theory of long strings and bootstrap techniques.Comment: 54 pages, 5 figure
Space-time S-matrix and Flux tube S-matrix II. Extracting and Matching Data
We elaborate on a non-perturbative formulation of scattering amplitudes/null
polygonal Wilson loops in planar N=4 Super-Yang-Mills theory. The construction
is based on a decomposition of the Wilson loop into elementary building blocks
named pentagon transitions. Our discussion expands on a previous letter of the
authors where these transitions were introduced and analyzed for the so-called
gluonic excitations. In this paper we revisit these transitions and extend the
analysis to the sector of scalar excitations. We restrict ourselves to the
single particle transitions and bootstrap their finite coupling expressions
using a set of axioms. Besides these considerations, the main focus of the
paper is on the extraction of perturbative data from scattering amplitudes at
weak coupling and its comparison against the proposed pentagon transitions. We
present several tests for both the hexagon and heptagon (MHV and NMHV)
amplitudes up to two- and three-loop orders. In attached notebooks we provide
explicit higher-loop predictions obtained from our method.Comment: 73 pages, 42 figures. v2,v3: typos correcte
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