11,715 research outputs found
Beta Function and Anomalous Dimensions
We demonstrate that it is possible to determine the coefficients of an
all-order beta function linear in the anomalous dimensions using as data the
two-loop coefficients together with the first one of the anomalous dimensions
which are universal. The beta function allows to determine the anomalous
dimension of the fermion masses at the infrared fixed point, and the resulting
values compare well with the lattice determinations.Comment: Version to match the published one in Phys. Rev. D. We added several
tables demonstrating how well the prediction for the anomalous dimensions at
the fixed point obtained via the all-orders beta function compares with the
one obtained in perturbation theory. We added also a figur
Anomalous Dimensions of Conformal Baryons
We determine the anomalous dimensions of baryon operators for the three color
theory as function of the number of massless flavours within the conformal
window to the maximum known order in perturbation theory. We show that the
anomalous dimension of the baryon is controllably small, within the
-expansion, for a wide range of number of flavours. We also find that
this is always smaller than the anomalous dimension of the fermion mass
operator. These findings challenge the partial compositeness paradigm.Comment: 4 pages, 4 figures. Matches published versio
Stabilization of Stochastic Quantum Dynamics via Open and Closed Loop Control
In this paper we investigate parametrization-free solutions of the problem of
quantum pure state preparation and subspace stabilization by means of
Hamiltonian control, continuous measurement and quantum feedback, in the
presence of a Markovian environment. In particular, we show that whenever
suitable dissipative effects are induced either by the unmonitored environment
or by non Hermitian measurements, there is no need for feedback control to
accomplish the task. Constructive necessary and sufficient conditions on the
form of the open-loop controller can be provided in this case. When open-loop
control is not sufficient, filtering-based feedback control laws steering the
evolution towards a target pure state are provided, which generalize those
available in the literature
Hot Conformal Gauge Theories
We compute the nonzero temperature free energy up to the order g^6 \ln(1/g)
in the coupling constant for vector like SU(N) gauge theories featuring matter
transforming according to different representations of the underlying gauge
group. The number of matter fields, i.e. flavors, is arranged in such a way
that the theory develops a perturbative stable infrared fixed point at zero
temperature. Due to large distance conformality we trade the coupling constant
with its fixed point value and define a reduced free energy which depends only
on the number of flavors, colors and matter representation.
We show that the reduced free energy changes sign, at the second, fifth and
sixth order in the coupling, when decreasing the number of flavors from the
upper end of the conformal window. If the change in sign is interpreted as
signal of an instability of the system then we infer a critical number of
flavors. Surprisingly this number, if computed to the order g^2, agrees with
previous predictions for the lower boundary of the conformal window for
nonsupersymmetric gauge theories. The higher order results tend to predict a
higher number of critical flavors. These are universal properties, i.e. they
are independent on the specific matter representation.Comment: RevTeX, 2-columns, 10 pages, 10 figure
Magnetic susceptibility and equation of state of N_f = 2+1 QCD with physical quark masses
We determine the free energy of strongly interacting matter as a function of
an applied constant and uniform magnetic field. We consider N_f = 2+1 QCD with
physical quark masses, discretized on a lattice by stout improved staggered
fermions and a tree level improved Symanzik pure gauge action, and explore
three different lattice spacings. For magnetic fields of the order of those
produced in non-central heavy ion collisions (eB ~ 0.1 GeV^2) strongly
interacting matter behaves like a medium with a linear response, and is
paramagnetic both above and below the deconfinement transition, with a
susceptibility which steeply rises in the deconfined phase. We compute the
equation of state, showing that the relative increase in the pressure due to
the magnetic field gets larger around the transition, and of the order of 10 %
for eB ~ 0.1 GeV^2.Comment: 11 pages, 10 figures, 3 tables. Final version published in Physical
Review
Ideal Walking Dynamics via a Gauged NJL Model
According to the Ideal Walking Technicolor paradigm large mass anomalous
dimensions arise in gauged Nambu--Jona-Lasinio (NJL) models when the
four-fermion coupling is sufficiently strong to induce spontaneous symmetry
breaking in an otherwise conformal gauge theory. We therefore study the
gauged NJL model with two adjoint fermions using lattice simulations. The model
is in an infrared conformal phase at small NJL coupling while it displays a
chirally broken phase at large NJL couplings. In the infrared conformal phase
we find that the mass anomalous dimension varies with the NJL coupling reaching
close to the chiral symmetry breaking transition, de facto
making the present model the first explicit realization of the Ideal Walking
scenario.Comment: 10 pages, 4 tables and 7 figure
Role of the unstable directions in the equilibrium and aging dynamics of supercooled liquids
The connectivity of the potential energy landscape in supercooled atomic
liquids is investigated through the calculation of the instantaneous normal
modes spectrum and a detailed analysis of the unstable directions in
configuration space. We confirm the hypothesis that the mode-coupling critical
temperature is the at which the dynamics crosses over from free to
activated exploration of configuration space. We also report the observed
changes in the local connectivity of configuration space sampled during aging,
following a temperature jump from a liquid to a glassy state.Comment: 5 pages, 3 figures. Phys. Rev. Lett., in pres
The sinking of the El Faro: predicting real world rogue waves during Hurricane Joaquin
We present a study on the prediction of rogue waves during the 1-hour sea
state of Hurricane Joaquin when the Merchant Vessel El Faro sank east of the
Bahamas on October 1, 2015. High-resolution hindcast of hurricane-generated sea
states and wave simulations are combined with novel probabilistic models to
quantify the likelihood of rogue wave conditions. The data suggests that the El
Faro vessel was drifting at an average speed of approximately~~m/s prior
to its sinking. As a result, we estimated that the probability that El Faro
encounters a rogue wave whose crest height exceeds 14 meters while drifting
over a time interval of 10~(50) minutes is ~. The largest
simulated rogue wave has similar generating mechanism and characteristics of
the Andrea, Draupner and Killard rogue waves as the constructive interference
of elementary waves enhanced by bound nonlinearities
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