3,740 research outputs found
(2,0) Superconformal OPEs in D=6, Selection Rules and Non-renormalization Theorems
We analyse the OPE of any two 1/2 BPS operators of (2,0) SCFT by
constructing all possible three-point functions that they can form with
another, in general long operator. Such three-point functions are uniquely
determined by superconformal symmetry. Selection rules are derived, which allow
us to infer ``non-renormalization theorems'' for an abstract superconformal
field theory. The latter is supposedly related to the strong-coupling dynamics
of coincident M5 branes, dual, in the large- limit, to the bulk
M-theory compactified on AdSS. An interpretation of extremal and
next-to-extremal correlators in terms of exchange of operators with protected
conformal dimension is given.Comment: some details correcte
Four-point correlators of BPS operators in N=4 SYM at order g^4
We study the large N degeneracy in the structure of the four-point amplitudes
of 1/2-BPS operators of arbitrary weight k in perturbative N=4 SYM theory. At
one loop (order g^2) this degeneracy manifests itself in a smaller number of
independent conformal invariant functions describing the amplitude, compared to
AdS_5 supergravity results. To study this phenomenon at the two-loop level
(order g^4) we consider a particular N=2 hypermultiplet projection of the
general N=4 amplitude. Using the formalism of N=2 harmonic superspace we then
explicitly compute this four-point correlator at two loops and identify the
corresponding conformal invariant functions. In the cases of 1/2-BPS operators
of weight k=3 and k=4 the one-loop large N degeneracy is lifted by the two-loop
corrections. However, for weight k > 4 the degeneracy is still there at the
two-loop level. This behavior suggests that for a given weight k the degeneracy
will be removed if perturbative corrections of sufficiently high order are
taken into account. These results are in accord with the AdS/CFT duality
conjecture.Comment: 45 pages, latex, 14 figure
Microscopic model of diffusion limited aggregation and electrodeposition in the presence of levelling molecules
A microscopic model of the effect of unbinding in diffusion limited
aggregation based on a cellular automata approach is presented. The geometry
resembles electrochemical deposition - ``ions'' diffuse at random from the top
of a container until encountering a cluster in contact with the bottom, to
which they stick. The model exhibits dendritic (fractal) growth in the
diffusion limited case. The addition of a field eliminates the fractal nature
but the density remains low. The addition of molecules which unbind atoms from
the aggregate transforms the deposit to a 100% dense one (in 3D). The molecules
are remarkably adept at avoiding being trapped. This mimics the effect of
so-called ``leveller'' molecules which are used in electrochemical deposition
Nonlinear field theories during homogeneous spatial dilation
The effect of a uniform dilation of space on stochastically driven nonlinear
field theories is examined. This theoretical question serves as a model problem
for examining the properties of nonlinear field theories embedded in expanding
Euclidean Friedmann-Lema\^{\i}tre-Robertson-Walker metrics in the context of
cosmology, as well as different systems in the disciplines of statistical
mechanics and condensed matter physics. Field theories are characterized by the
speed at which they propagate correlations within themselves. We show that for
linear field theories correlations stop propagating if and only if the speed at
which the space dilates is higher than the speed at which correlations
propagate. The situation is in general different for nonlinear field theories.
In this case correlations might stop propagating even if the velocity at which
space dilates is lower than the velocity at which correlations propagate. In
particular, these results imply that it is not possible to characterize the
dynamics of a nonlinear field theory during homogeneous spatial dilation {\it a
priori}. We illustrate our findings with the nonlinear Kardar-Parisi-Zhang
equation
Studies of discharge mechanisms in high pressure gases-applications to high efficiency high power lasers
By measuring the absorption and emission cantinua of various states in the cesium/xenon molecule, the collisional rates critical in populating the alkali/rare gas excimer levels have been estimated. Cs atomic states that are weakly optically connected to ground have been shown to form excimer levels that are attractive as potential dissociation lasers. In particular, the (Cs/7 2S/Xe) excited molecule appears promising as a source of high energy laser radiation due to its large dissociation energy, stimulated emission cross section, and small population inversion densities. Monitoring of the optically pumped Cs2 molecular absorption profile in the presence of xenon shows a drastic change with increasing xenon pressure for the Cs2C band. Dominant absorption at large xenon densities is centered around approximately 6380 A as opposed to 6300 A for lower perturber pressure
Double logarithmical corrections to beam asymmetry in polarized electron-proton scattering
The up-down asymmetry in transversally polarized electron proton scattering
is induced by the interference between one and two photon exchange amplitudes.
Inelastic intermediate hadronic states (different from one-proton state) of the
two photon exchange amplitude give rise to contributions containing the square
of "large logarithm" (logarithm of the ratio of the transferred momentum to the
electron mass). We investigate the presence of such contributions in higher
orders of perturbation theory. The relation with the case of zero transfer
momentum is explicitly given. The mechanism of cancellation of infrared
singularities is discussed.Comment: 9 pages, 8 figure
Estimated 2020 CO2 Emission Reductions in Virginia’s Transportation Sector from COVID-19
The initial lockdown phase of the COVID-19 pandemic presented an unfortunate opportunity to observe how abrupt, large-scale changes in traffic volume can reduce greenhouse gas emissions. This study explores how carbon dioxide (CO2) emissions from Virginia’s transportation sector may have been affected by the changes in activity stemming from COVID-19 to inform more carbon-neutral policies as the state recovers from the economic downfall. Emission savings were calculated by multiplying the percent change from 2019 to 2020 in traffic volume from the Virginia Department of Transportation with the business-as-usual 2020 U.S. Environmental Protection Agency estimate of CO2 emissions for Virginia’s transportation sector. We estimate Virginia’s 2020 COVID-19 transportation CO2 emissions reduction is around 15.0% (14.2 to 15.7%), with reduced passenger vehicle traffic making up the bulk of the inferred reduction. This study highlights the utility of reimagining our current transportation sector as a way to implement sustainable, state-level carbon reduction policies, such as the Clean Car Standards
Universal properties of superconformal OPEs for 1/2 BPS operators in
We give a general analysis of OPEs of 1/2 BPS superfield operators for the
superconformal algebras OSp(8/4,R), PSU(2,2), F and
OSp() which underlie maximal AdS supergravity in . \\
The corresponding three-point functions can be formally factorized in a way
similar to the decomposition of a generic superconformal UIR into a product of
supersingletons. This allows for a simple derivation of branching rules for
primary superfields. The operators of protected conformal dimension which may
appear in the OPE are classified and are shown to be either 1/2 or 1/4 BPS, or
semishort. As an application, we discuss the "non-renormalization" of extremal
-point correlators.Comment: To be published in NJP Focus Issue: Supersymmetry in condensed matter
and high energy physic
AdS/SCFT in Superspace
A discussion of the AdS/CFT correspondence in IIB is given in a superspace
context. The main emphasis is on the properties of SCFT correlators on the
boundary which are studied using harmonic superspace techniques. These
techniques provide the easiest way of implementing the superconformal Ward
identities. The Ward identities, together with analyticity, can be used to give
a compelling argument in support of the non-renormalisation theorems for two-
and three-point functions, and to establish the triviality of extremal and
next-to-extremal correlation functions. The OPE in is also briefly discussed.Comment: 10 pages; talk given by PSH at 2nd Gursey Memorial Conference, June
200
From correlation functions to scattering amplitudes
We study the correlators of half-BPS protected operators in N=4
super-Yang-Mills theory, in the limit where the positions of the adjacent
operators become light-like separated. We compute the loop corrections by means
of Lagrangian insertions. The divergences resulting from the light-cone limit
are regularized by changing the dimension of the integration measure over the
insertion points. Switching from coordinates to dual momenta, we show that the
logarithm of the correlator is identical with twice the logarithm of the
matching MHV gluon scattering amplitude. We present a number of examples of
this new relation, at one and two loops.Comment: typos corrected, references adde
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