39,288 research outputs found
A New Formulation of the Initial Value Problem for Nonlocal Theories
There are a number of reasons to entertain the possibility that locality is
violated on microscopic scales, for example through the presence of an infinite
series of higher derivatives in the fundamental equations of motion. This type
of nonlocality leads to improved UV behaviour, novel cosmological dynamics and
is a generic prediction of string theory. On the other hand, fundamentally
nonlocal models are fraught with complications, including instabilities and
complications in setting up the initial value problem. We study the structure
of the initial value problem in an interesting class of nonlocal models. We
advocate a novel new formulation wherein the Cauchy surface is "smeared out"
over the underlying scale of nonlocality, so that the the usual notion of
initial data at t=0 is replaced with an "initial function" defined over -M^{-1}
\leq t \leq 0 where M is the underlying scale of nonlocality. Focusing on some
specific examples from string theory and cosmology, we show that this
mathematical re-formulation has surprising implications for the well-known
stability problem. For D-brane decay in a linear dilaton background, we are
able to show that the unstable directions in phase space cannot be accessed
starting from a physically sensible initial function. Previous examples of
unstable solutions in this model therefore correspond to unphysical initial
conditions, an observation which is obfuscated in the old formulation of the
initial value problem. We also discuss implication of this approach for
nonlocal cosmological models.Comment: 36 pages, 9 figures. Accepted for publication in Nuclear Physics
Semiclassical Strings in Supergravity PFT
Puff Field Theory (PFT) is an example of a non-local field theory which
arises from a novel embedding of D-branes in Melvin universe. We study several
rotating and pulsating string solutions of the F-string equations of motion in
the supergravity dual of the PFT. Further, we find a PP-wave geometry from this
nonlocal spacetime by applying a Penrose limit and comment on its similarity
with the maximally supersymmetric PP-wave background.Comment: 21 pages, added clarification
Draining the Water Hole: Mitigating Social Engineering Attacks with CyberTWEAK
Cyber adversaries have increasingly leveraged social engineering attacks to
breach large organizations and threaten the well-being of today's online users.
One clever technique, the "watering hole" attack, compromises a legitimate
website to execute drive-by download attacks by redirecting users to another
malicious domain. We introduce a game-theoretic model that captures the salient
aspects for an organization protecting itself from a watering hole attack by
altering the environment information in web traffic so as to deceive the
attackers. Our main contributions are (1) a novel Social Engineering Deception
(SED) game model that features a continuous action set for the attacker, (2) an
in-depth analysis of the SED model to identify computationally feasible
real-world cases, and (3) the CyberTWEAK algorithm which solves for the optimal
protection policy. To illustrate the potential use of our framework, we built a
browser extension based on our algorithms which is now publicly available
online. The CyberTWEAK extension will be vital to the continued development and
deployment of countermeasures for social engineering.Comment: IAAI-20, AICS-2020 Worksho
Precision Spectroscopy of AdS/CFT
We extend recent remarkable progress in the comparison of the dynamical
energy spectrum of rotating closed strings in AdS_5xS^5 and the scaling weights
of the corresponding non-near-BPS operators in planar N=4 supersymmetric gauge
theory. On the string side the computations are feasible, using semiclassical
methods, if angular momentum quantum numbers are large. This results in a
prediction of gauge theory anomalous dimensions to all orders in the `t Hooft
coupling lambda. On the gauge side the direct computation of these dimensions
is feasible, using a recently discovered relation to integrable (super) spin
chains, provided one considers the lowest order in lambda. This one-loop
computation then predicts the small-tension limit of the string spectrum for
all (i.e. small or large) quantum numbers. In the overlapping window of large
quantum numbers and small effective string tension, the string theory and gauge
theory results are found to match in a mathematically highly non-trivial
fashion. In particular, we compare energies of states with (i) two large
angular momenta in S^5, and (ii) one large angular momentum in AdS_5 and S^5
each, and show that the solutions are related by an analytic continuation.
Finally, numerical evidence is presented on the gauge side that the agreement
persists also at higher (two) loop order.Comment: 26 pages, 1 figure, v2: typos correcte
Nonrelativistic Corners of Supersymmetric Yang--Mills Theory
We show that supersymmetric-Yang-Mills (SYM) theory on
with gauge group is described in a
near-BPS limit by a simple lower-dimensional nonrelativistic field theory with
invariant interactions. In this limit, a
single complex adjoint scalar field survives, and part of its interaction is
obtained by exactly integrating out the gauge boson of the SYM theory. Taking
into account normal ordering, the interactions match the one-loop dilatation
operator of the sector, establishing the consistency of the
limit at the quantum level. We discover a tantalizing field-theoretic
structure, corresponding to a -dimensional complex chiral boson on a
circle coupled to a nondynamical gauge field, both in the adjoint
representation of . The successful construction of a
lower-dimensional nonrelativistic field theory in the near-BPS
limit provides a proof of concept for other BPS bounds. These are expected to
lead to richer field theories in nonrelativistic corners of SYM
that include fermions, gauge fields and supersymmetry and can provide a novel
path towards understanding strongly coupled finite- dynamics of gauge
theories.Comment: 6 pages, 1 figure; v2: minor clarifications added, matches journal
versio
- …