6,279 research outputs found
The UV behavior of Gravity at Large N
A first step in the analysis of the renormalizability of gravity at Large N
is carried on. Suitable resummations of planar diagrams give rise to a theory
in which there is only a finite number of primitive superficially divergent
Feynman diagrams. The mechanism is similar to the the one which makes
renormalizable the 3D Gross-Neveu model at large N. Some potential problems in
fulfilling the Slavnov-Taylor and the Zinn-Justin equations are also pointed
out.Comment: 17 pages, 9 figures. To appear on Phys. Rev. D. Two more references,
further technical details and the discussion of the KLT relations at large N
have been include
Optimal Single-Choice Prophet Inequalities from Samples
We study the single-choice Prophet Inequality problem when the gambler is
given access to samples. We show that the optimal competitive ratio of
can be achieved with a single sample from each distribution. When the
distributions are identical, we show that for any constant ,
samples from the distribution suffice to achieve the optimal competitive
ratio () within , resolving an open problem of
Correa, D\"utting, Fischer, and Schewior.Comment: Appears in Innovations in Theoretical Computer Science (ITCS) 202
A New Approach to Flavor Symmetry and an Extended Naturalness Principle
A class of non-supersymmetric extensions of the Standard Model is proposed in
which there is a multiplicity of light scalar doublets in a multiplet of a
non-abelian family group with the Standard Model Higgs doublet. Anthropic
tuning makes the latter light, and consequently the other scalar doublets
remain light because of the family symmetry. The family symmetry greatly
constrains the pattern of FCNC and proton decay operators coming from
scalar-exchange. Such models show that useful constraints on model-building can
come from an extended naturalness principle when the electroweak scale is
anthropically tuned.Comment: 31 pages, 3 figure
Scale invariant Euclidean field theory in any dimension
We discuss D-dimensional scalar field interacting with a scale invariant
random metric which is either a Gaussian field or a square of a Gaussian field.
The metric depends on d-dimensional coordinates (where d is less than D). By a
projection to a lower dimensional subspace we obtain a scale invariant
non-Gaussian model of Euclidean quantum field theory in D-d or d dimensions.Comment: Latex, 16 page
Heavy Quark Potentials in Some Renormalization Group Revised AdS/QCD Models
We construct some AdS/QCD models by the systematic procedure of GKN. These
models reflect three rather different asymptotics the gauge theory beta
functions approach at the infrared region,
and , where is the 't Hooft coupling constant.
We then calculate the heavy quark potentials in these models by holographic
methods and find that they can more consistently fit the lattice data relative
to the usual models which do not include the renormalization group improving
effects. But only use the lattice QCD heavy quark potentials as constrains, we
cannot distinguish which kind of infrared asymptotics is the better one.Comment: comparisons with lattice results, qualitative consideration of
quantum corrections are added. (accepted by Phys. Rev. D
Feshbach Resonances and Limiting Thermodynamics of Strongly Correlated Nucleons
A finite temperature model of strongly correlated nucleons with underlying
isospin symmetries is developed. The model can be used to study the role of
bound states and Feshbach resonances on the thermal properties of a spin 1/2,
isospin 1/2 system of protons and neutrons by varying the proton fraction. An
analysis of features associated with a universal thermodynamic limit or unitary
limit is given. In the limit of very large scattering length, the effective
range to quantum thermal wavelength appears as a limiting scale in an
interaction energy and equation of state.Comment: 8 pages, 4 figure
The footprint of E7 in amplitudes of N=8 supergravity
We study the low energy theorems associated with the non-linearly realized
continuous E7 symmetry of the on-shell N=8 supergravity. For Nambu-Goldstone
bosons we evaluate the one-soft-scalar-bosonemission amplitudes by computing
the E7 current matrix element on the one-particle external lines. We use the
explicit form of the conserved E7 Noether current and prove that all such
matrix elements vanish in the soft momentum limit,assuming the SU(8) symmetry
of the S-matrix.This implies that all tree amplitudes vanish in the
one-soft-boson limit. We also discuss the implications of unbroken E7 symmetry
for higher-order amplitudes.Comment: 18 p., 2 figure
Gauge Invariant Treatment of the Electroweak Phase Transition
We evaluate the gauge invariant effective potential for the composite field
in the SU(2)-Higgs model at finite temperature.
Symmetric and broken phases correspond to the domains and
, respectively. The effective potential increases very steeply
at small values of . Predictions for several observables, derived from
the ordinary and the gauge invariant effective potential, are compared. Good
agreement is found for the critical temperature and the jump in the order
parameter. The results for the latent heat differ significantly for large Higgs
masses.Comment: 8 pages latex, DESY-94-043, 4 figures can be obtained via e-mail from
[email protected]
Algorithmic Bayesian Persuasion
Persuasion, defined as the act of exploiting an informational advantage in
order to effect the decisions of others, is ubiquitous. Indeed, persuasive
communication has been estimated to account for almost a third of all economic
activity in the US. This paper examines persuasion through a computational
lens, focusing on what is perhaps the most basic and fundamental model in this
space: the celebrated Bayesian persuasion model of Kamenica and Gentzkow. Here
there are two players, a sender and a receiver. The receiver must take one of a
number of actions with a-priori unknown payoff, and the sender has access to
additional information regarding the payoffs. The sender can commit to
revealing a noisy signal regarding the realization of the payoffs of various
actions, and would like to do so as to maximize her own payoff assuming a
perfectly rational receiver.
We examine the sender's optimization task in three of the most natural input
models for this problem, and essentially pin down its computational complexity
in each. When the payoff distributions of the different actions are i.i.d. and
given explicitly, we exhibit a polynomial-time (exact) algorithm, and a
"simple" -approximation algorithm. Our optimal scheme for the i.i.d.
setting involves an analogy to auction theory, and makes use of Border's
characterization of the space of reduced-forms for single-item auctions. When
action payoffs are independent but non-identical with marginal distributions
given explicitly, we show that it is #P-hard to compute the optimal expected
sender utility. Finally, we consider a general (possibly correlated) joint
distribution of action payoffs presented by a black box sampling oracle, and
exhibit a fully polynomial-time approximation scheme (FPTAS) with a bi-criteria
guarantee. We show that this result is the best possible in the black-box model
for information-theoretic reasons
Antibodies from patients with myasthenia gravis recognize determinants unique to extrajunctional acetylcholine receptors.
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