6,085 research outputs found
The effects of isometric work on heart rate, blood pressure, and net oxygen cost
Isometric exercise effects on heart rate, blood pressure, and net oxygen cos
Saturation Effects in Deep Inelastic Scattering at low and its Implications on Diffraction
We present a model based on the concept of saturation for small and
small . With only three parameters we achieve a good description of all Deep
Inelastic Scattering data below . This includes a consistent treatment
of charm and a successful extrapolation into the photoproduction regime. The
same model leads to a roughly constant ratio of diffractive and inclusive cross
section.Comment: 24 pages, 12 figures, Latex-fil
Geometric Scaling in Inclusive Charm Production
We show that the cross section for inclusive charm production exhibits
geometric scaling in a large range of photon virtualities. In the HERA
kinematic domain the saturation momentum stays below the hard
scale , implying charm production probing mostly the color
transparency regime and unitarization effects being almost negligible. We
derive our results considering two saturation models which are able to describe
the DESY ep collider HERA data for the proton structure function at small
values of the Bjorken variable . A striking feature is the scaling on
above saturation limit, corroborating recent
theoretical studies.Comment: 4 pages, 2 figures. Version to be published in Physical Review
Letter
Graviton emission in Einstein-Hilbert gravity
The five-point amplitude for the scattering of two distinct scalars with the
emission of one graviton in the final state is calculated in exact kinematics
for Einstein-Hilbert gravity. The result, which satisfies the Steinmann
relations, is expressed in Sudakov variables, finding that it corresponds to
the sum of two gauge invariant contributions written in terms of a new two
scalar - two graviton effective vertex. A similar calculation is carried out in
Quantum Chromodynamics (QCD) for the scattering of two distinct quarks with one
extra gluon in the final state. The effective vertices which appear in both
cases are then evaluated in the multi-Regge limit reproducing the well-known
result obtained by Lipatov where the Einstein-Hilbert graviton emission vertex
can be written as the product of two QCD gluon emission vertices, up to
corrections to preserve the Steinmann relations.Comment: 28 pages, LaTeX, feynmf. v2: typos corrected, reference added. Final
version to appear in Journal of High Energy Physic
Survival probability of large rapidity gaps in QCD and N=4 SYM motivated model
In this paper we present a self consistent theoretical approach for the
calculation of the Survival Probability for central dijet production . These
calculations are performed in a model of high energy soft interactions based on
two ingredients:(i) the results of N=4 SYM, which at the moment is the only
theory that is able to deal with a large coupling constant; and (ii) the
required matching with high energy QCD. Assuming, in accordance with these
prerequisites, that soft Pomeron intercept is rather large and the slope of the
Pomeron trajectory is equal to zero, we derive analytical formulae that sum
both enhanced and semi-enhanced diagrams for elastic and diffractive
amplitudes. Using parameters obtained from a fit to the available experimental
data, we calculate the Survival Probability for central dijet production at
energies accessible at the LHC. The results presented here which include the
contribution of semi-enhanced and net diagrams, are considerably larger than
our previous estimates.Comment: 11 pages, 10 pictures in .eps file
Combined electrical transport and capacitance spectroscopy of a field effect transistor
We have measured both the current-voltage (-)
and capacitance-voltage (-) characteristics of a
field effect transistor. From the measured capacitance
we calculate the electron surface density and show that its gate voltage
dependence follows the theoretical prediction resulting from the
two-dimensional free electron model. This model allows us to fit the measured
- characteristics over the \emph{entire range} of
. Combining this experimental result with the measured
current-voltage characteristics, we determine the field effect mobility as a
function of gate voltage. We show that for our device this improved combined
approach yields significantly smaller values (more than a factor of 4) of the
electron mobility than the conventional analysis of the current-voltage
characteristics only.Comment: to appear in Applied Physics Letter
The casuality and/or energy-momentum conservation constraints on QCD amplitudes in small x regime
The causality and/or the energy-momentum constraints on the amplitudes of
high energy processes are generalized to QCD. The constraints imply that the
energetic parton may experience at most one inelastic collision only and that
the number of the constituents in the light cone wave function of the
projectile is increasing with the collision energy and the atomic number.Comment: 24 pages,8 figures. The paper is streamlined, some references are
changed and misprints are eliminate
Odderon in the Color Glass Condensate
We discuss the definition and the energy evolution of scattering amplitudes
with -odd ("odderon") quantum numbers within the effective theory for the
Color Glass Condensate (CGC) endowed with the functional, JIMWLK, evolution
equation. We explicitly construct gauge-invariant amplitudes describing
multiple odderon exchanges in the scattering between the CGC and two types of
projectiles: a color--singlet quark--antiquark pair (or `color dipole') and a
system of three quarks in a colorless state. We deduce the energy evolution of
these amplitudes from the general JIMWLK equation, which for this purpose is
recast in a more synthetic form, which is manifestly infrared finite. For the
dipole odderon, we confirm and extend the non--linear evolution equations
recently proposed by Kovchegov, Szymanowski and Wallon, which couple the
evolution of the odderon to that of the pomeron, and predict the rapid
suppression of the odderon exchanges in the saturation regime at high energy.
For the 3--quark system, we focus on the linear regime at relatively low
energy, where our general equations are shown to reduce to the
Bartels--Kwiecinski--Praszalowicz equation. Our gauge--invariant amplitudes,
and the associated evolution equations, stay explicitly outside the M\"obius
representation, which is the Hilbert space where the BFKL Hamiltonian exhibits
holomorphic separability.Comment: 43 pages, 1 figur
Four point function of R-currents in N=4 SYM in the Regge limit at weak coupling
We compute, in N=4 super Yang-Mills theory, the four point correlation
function of R-currents in the Regge limit in the leading logarithmic
approximation at weak coupling. Such a correlator is the closest analog to
photon-photon scattering within QCD, and there is a well-defined procedure to
perform the analogous computation at strong coupling via the AdS/CFT
correspondence. The main result of this paper is, on the gauge theory side, the
proof of Regge factorization and the explicit computation of the R-current
impact factors.Comment: 21 pages, 10 figures, typos correcte
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