177,803 research outputs found
Exclusive diffractive electroproduction of dijets in collinear factorization
Exclusive electroproduction of hard dijets can be described within the
collinear factorization. This process has clear experimental signature and
provides one with an interesting alternative venue to test QCD description of
hard diffractive processes and extract information on generalized nucleon
parton distributions. In this work we present detailed leading-order QCD
calculations of the relevant cross sections, including longitudinal momentum
fraction distribution of the dijets and their azimuthal angle dependence.Comment: 11 pages, 14 Postscript figures, uses revtex4.st
Analysis of clustering phenomena in ab initio approaches
An approach for explicit consideration of cluster effects in nuclear systems
and accurate ab initio calculations of cluster characteristics of nuclei is
devised. The essential block of the approach is a construction of a basis which
incorporates both conventional No-Core Shell Model wave functions and
translationally-invariant wave functions of various cluster channels. The
results of computations of the total binding energies of 8Be nucleus as well as
the spectroscopic factors of cluster channels (amount of clustering) are
presented. An unexpected fresh result of the rigorous study is that the
contribution of "non-clustered" components of the basis to the total binding
energy is great even in the typical cluster systems such as the discussed
nucleus
New critical behavior in unconventional ferromagnetic superconductors
New critical behavior in unconventional superconductors and superfluids is
established and described by the Wilson-Fisher renormalization-group method.
For certain ordering symmetries a new type of fluctuation-driven first order
phase transitions at finite and zero temperature are predicted. The results can
be applied to a wide class of ferromagnetic superconducting and superfluid
systems, in particular, to itinerant ferromagnets as UGe2 and URhGe.Comment: 12 pages, 6 fig
Curvature Expansion for the Gluodynamics String including Perturbative Gluonic Contributions
Perturbation theory in the nonperturbative QCD vacuum and the non-Abelian
Stokes theorem, representing a Wilson loop in the SU(2) gluodynamics as an
integral over all the orientations in colour space, are applied to a derivation
of the correction to the string effective action in the lowest order in the
coupling constant . This correction is due to the interaction of
perturbative gluons with the string world sheet and affects only the coupling
constant of the rigidity term, while its contribution to the string tension of
the Nambu-Goto term vanishes. The obtained correction to the rigidity coupling
constant multiplicatively depends on the colour "spin" of the representation of
the Wilson loop under consideration and a certain path integral, which includes
the background Wilson loop average.Comment: 9 pages, LaTeX, no figure
Stripping Cross Sections in Collisions of Light Nuclei
By evaluating all the contributions of the intermediate states of the
multiple scattering theory diagrams, we compute the integrated stripping cross
sections of collisions among light nuclei. The resulting expressions have the
simple form of a combination of total inelastic cross sections of nuclear
reactions with projectile nuclei differing in the atomic mass number. We also
check the accuracy of some widely used relations in heavy ion collisions.Comment: 9 pages, 4 figures, Latex fil
Quantum Friction of Micromechanical Resonators at Low Temperatures
Dissipation of micro- and nano-scale mechanical structures is dominated by
quantum-mechanical tunneling of two-level defects intrinsically present in the
system. We find that at high frequencies--usually, for smaller, micron-scale
structures--a novel mechanism of phonon pumping of two-level defects gives rise
to weakly temperature-dependent internal friction, , concomitant to the
effects observed in recent experiments. Due to their size, comparable to or
shorter than the emitted phonon wavelength, these structures suffer from
superradiance-enhanced dissipation by the collective relaxation of a large
number of two-level defects contained within the wavelength.Comment: To apear in Phys. Rev. Let
Current fluctuations in composite conductors: Beyond the second cumulant
Employing the non-linear -model we analyze current fluctuations in
coherent composite conductors which contain a diffusive element in-between two
tunnel barriers. For such systems we explicitly evaluate the
frequency-dependent third current cumulant which also determines the leading
Coulomb interaction correction to shot noise. Our predictions can be directly
tested in future experiments.Comment: 6 pages, 1 figur
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