17,575 research outputs found
Josephson current in a superconductor -- ferromagnet -- superconductor junction with in-plane ferromagnetic domains
We study a diffusive superconductor--ferromagnet--superconductor (SFS)
junction with in-plane ferromagnetic domains. Close to the superconducting
transition temperature, we describe the proximity effect in the junction with
the linearized Usadel equations. We find that properties of such a junction
depend on the size of the domains relative to the magnetic coherence length. In
the case of large domains, the junction exhibits transitions to the
state, similarly to a single-domain SFS junction. In the case of small domains,
the magnetization effectively averages out, and the junction is always in the
zero state, similarly to a superconductor--normal metal--superconductor (SNS)
junction. In both those regimes, the influence of domain walls may be
approximately described as an effective spin-flip scattering. We also study the
inhomogeneous distribution of the local current density in the junction. Close
to the 0-- transitions, the directions of the critical current may be
opposite in the vicinity of the domain wall and in the middle of the domains.Comment: 9 pages, 6 figure
Self-gravitating spheres of anisotropic fluid in geodesic flow
The fluid models mentioned in the title are classified. All characteristics
of the fluid are expressed through a master potential, satisfying an ordinary
second order differential equation. Different constraints are imposed on this
core of relations, finding new solutions and deriving the classical results for
perfect fluids and dust as particular cases. Many uncharged and charged
anisotropic solutions, all conformally flat and some uniform density solutions
are found. A number of solutions with linear equation among the two pressures
are derived, including the case of vanishing tangential pressure.Comment: 21 page
Relativistic Heavy-Ion Collisions within 3-Fluid Hydrodynamics: Hadronic Scenario
A 3-fluid hydrodynamic model for simulating relativistic heavy-ion collisions
is introduced. Alongside with two baryon-rich fluids, the new model considers
time-delayed evolution of a third, baryon-free (i.e. with zero net baryonic
charge) fluid of newly produced particles. Its evolution is delayed due to a
formation time, during which the baryon-free fluid neither thermalizes nor
interacts with the baryon-rich fluids. After the formation it starts to
interact with the baryon-rich fluids and quickly gets thermalized. Within this
model with pure hadronic equation of state, a systematic analysis of various
observables at incident energies between few and about 160A GeV has been done
as well as comparison with results of transport models. We have succeeded to
reasonably reproduce a great body of experimental data in the incident energy
range of E_{lab} = (1-160)A GeV. The list includes proton and pion rapidity
distributions, proton transverse-mass spectra, rapidity distributions of Lambda
and antiLambda hyperons, elliptic flow of protons and pions (with the exception
of proton v2 at 40A GeV), multiplicities of pions, positive kaons, phi-mesons,
hyperons and antihyperons, including multi-strange particles. This agreement is
achieved on the expense of substantial enhancement of the interflow friction as
compared to that estimated proceeding from hadronic free cross sections.
However, we have also found out certain problems. The calculated yield of K^-
is approximately by a factor of 1.5 higher than that in the experiment. We have
also failed to describe directed transverse flow of protons and pion at E_{lab}
> 40A GeV. This failure apparently indicates that the used EoS is too hard and
thereby leaves room for a phase transition.Comment: 30 pages, 20 figures, 2 tables. Version accepted for publication in
Phys. Rev.
Probing GPDs in photoproduction processes at hadron colliders
Generalized parton distributions (GPDs) enter QCD factorization theorems for
hard exclusive reactions. They encode rich information about hadron partonic
structure. We explore a possibility to constrain GPDs in experiments at LHC
considering two different exclusive processes: the timelike Compton scattering
and the photoproduction of heavy vector mesons.Comment: 6 pages, 2 figures; presented at PHOTON 2015: International
Conference on the Structure and the Interactions of the Photon, Novosibirsk,
Russia, 15 - 19 June, 2015. arXiv admin note: text overlap with
arXiv:1411.375
Probing GPDs in Ultraperipheral Collisions
Ultraperipheral collisions in hadron colliders give new opportunites to
investigate the hadron stucture through exclusive photoproduction processes. We
describe the possibility of measuring the Generalized Parton Distributions in
the Timelike Compton Scattering process and in the production of heavy vector
meson.Comment: to appear in Proceedings Diffraction 2014, Primosten, Croatia, sept
10-16, 201
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