1,917 research outputs found
Conservative boundary conditions for 3D gas dynamics problems
A method is described for 3D-gas dynamics computer simulation in regions of complicated shape by means of nonadjusted rectangular grids providing unified treatment of various problems. Some test problem computation results are given
Low energy theorem for virtual Compton scattering and generalized sum rules of the nucleon
We formulate the low energy theorem for virtual Compton scattering off a
nucleon and examine its consequences for generalized nucleon polarizabilites.
As a result of a new, model independent definition of the low energy limit for
VVCS reaction, all generalized sum rules of the nucleon have continuous limit
for real photons and obtain contributions from the -channel that were not
included previously.Comment: 4 pages, 2 figures, revtex
On q-deformed gl(l+1)-Whittaker function II
A representation of a specialization of a q-deformed class one lattice
gl(\ell+1}-Whittaker function in terms of cohomology groups of line bundles on
the space QM_d(P^{\ell}) of quasi-maps P^1 to P^{\ell} of degree d is proposed.
For \ell=1, this provides an interpretation of non-specialized q-deformed
gl(2)-Whittaker function in terms of QM_d(\IP^1). In particular the (q-version
of) Mellin-Barnes representation of gl(2)-Whittaker function is realized as a
semi-infinite period map. The explicit form of the period map manifests an
important role of q-version of Gamma-function as a substitute of topological
genus in semi-infinite geometry. A relation with Givental-Lee universal
solution (J-function) of q-deformed gl(2)-Toda chain is also discussed.Comment: Extended version submitted in Comm. Math. Phys., 24 page
Non-Perturbative Tachyon Potential from the Wilsonian Renormalization Group
The derivative expansion of the Wilsonian renormalization group generates
additional terms in the effective beta-functions not present in the
perturbative approach. Applied to the nonlinear sigma model, to lowest order
the vanishing of the beta-function for the tachyon field generates an equation
analogous to that found in open string field theory. Although the nonlinear
term depends on the cut-off function, this arbitrariness can be removed by a
rescaling of the tachyon field.Comment: 6 pages, further references adde
Quantum matter wave dynamics with moving mirrors
When a stationary reflecting wall acting as a perfect mirror for an atomic
beam with well defined incident velocity is suddenly removed, the density
profile develops during the time evolution an oscillatory pattern known as
diffraction in time. The interference fringes are suppressed or their
visibility is diminished by several effects such as averaging over a
distribution of incident velocities, apodization of the aperture function,
atom-atom interactions, imperfect reflection or environmental noise. However,
when the mirror moves with finite velocity along the direction of propagation
of the beam, the visibility of the fringes is enhanced. For mirror velocities
below beam velocity, as used for slowing down the beam, the matter wave splits
into three regions separated by space-time points with classical analogues. For
mirror velocities above beam velocity a visibility enhancement occurs without a
classical counterpart. When the velocity of the beam approaches that of the
mirror the density oscillations rise by a factor 1.8 over the stationary value.Comment: 5.2 pages, 6 figure
The Boundary State Formalism and Conformal Invariance in Off-shell String Theory
We present a generalization of the boundary state formalism for the bosonic
string that allows us to calculate the overlap of the boundary state with
arbitrary closed string states. We show that this generalization exactly
reproduces world-sheet sigma model calculations, thus giving the correct
overlap with both on- and off-shell string states, and that this new boundary
state automatically satisfies the requirement for integrated vertex operators
in the case of non-conformally invariant boundary interactions.Comment: 19 pages, 0 figure
Determination of gas temperature in the plasmatron channel according to the known distribution of electronic temperature
An analytical method to calculate the temperature distribution of heavy
particles in the channel of the plasma torch on the known distribution of the
electronic temperature has been proposed. The results can be useful for a
number of model calculations in determining the most effective conditions of
gas blowing through the plasma torch with the purpose of heating the heavy
component. This approach allows us to understand full details about the
heating of cold gas, inpouring the plasma, and to estimate correctly the
distribution of the gas temperature inside the channel
Proton structure corrections to electronic and muonic hydrogen hyperfine splitting
We present a precise determination of the polarizability and other proton
structure dependent contributions to the hydrogen hyperfine splitting, based
heavily on the most recent published data on proton spin dependent structure
functions from the EG1 experiment at the Jefferson Laboratory. As a result, the
total calculated hyperfine splitting now has a standard deviation slightly
under 1 part-per-million, and is about 1 standard deviation away from the
measured value. We also present results for muonic hydrogen hyperfine
splitting, taking care to ensure the compatibility of the recoil and
polarizability terms.Comment: 9 pages, 1 figur
- …