2,275 research outputs found
Quasi-Particle Spectra, Charge-Density-Wave, Superconductivity and Electron-Phonon Coupling in 2H-NbSe2
High-resolution photoemission has been used to study the electronic structure
of the charge density wave (CDW) and superconducting (SC) dichalcogenide, 2H-
NbSe2. From the extracted self-energies, important components of the
quasiparticle (QP) interactions have been identified. In contrast to previously
studied TaSe2, the CDW transition does not affect the electronic properties
significantly. The electron-phonon coupling is identified as a dominant
contribution to the QP self-energy and is shown to be very anisotropic
(k-dependent) and much stronger than in TaSe2.Comment: 4 pages, 3 figures, minor changes, to appear in PR
Giant vortices, vortex rings and reentrant behavior in type-1.5 superconductors
We predict that in a bulk type-1.5 superconductor the competing magnetic
responses of the two components of the order parameter can result in a vortex
interaction that generates group-stabilized giant vortices and unusual vortex
rings in the absence of any extrinsic pinning or confinement mechanism. We also
find within the Ginzburg-Landau theory a rich phase diagram with successions of
behaviors like type-1 -> type-1.5 -> type-2 -> type-1.5 as temperature
decreases.Comment: 5 pages, 4 figure
High--Energy Photon--Hadron Scattering in Holographic QCD
This article provides an in-depth look at hadron high energy scattering by
using gravity dual descriptions of strongly coupled gauge theories. Just like
deeply inelastic scattering (DIS) and deeply virtual Compton scattering (DVCS)
serve as clean experimental probes into non-perturbative internal structure of
hadrons, elastic scattering amplitude of a hadron and a (virtual) "photon" in
gravity dual can be exploited as a theoretical probe. Since the scattering
amplitude at sufficiently high energy (small Bjorken x) is dominated by parton
contributions (= Pomeron contributions) even in strong coupling regime, there
is a chance to learn a lesson for generalized parton distribution (GPD) by
using gravity dual models. We begin with refining derivation of
Brower-Polchinski-Strassler-Tan (BPST) Pomeron kernel in gravity dual, paying
particular attention to the role played by complex spin variable j. The BPST
Pomeron on warped spacetime consists of a Kaluza-Klein tower of 4D Pomerons
with non-linear trajectories, and we clarify the relation between Pomeron
couplings and Pomeron form factor. We emphasize that the saddle point value j^*
of the scattering amplitude in the complex j-plane representation is a very
important concept in understanding qualitative behavior of the scattering
amplitude. The total Pomeron contribution to the scattering is decomposed into
the saddle point contribution and at most a finite number of pole
contributions, and when the pole contributions are absent (which we call saddle
point phase), kinematical variable (q,x,t) dependence of ln (1/q) evolution and
ln(1/x) evolution parameters gamma_eff. and lambda_eff. in DIS and t-slope
parameter B of DVCS in HERA experiment are all reproduced qualitatively in
gravity dual
Static and Dynamic Phases for Vortex Matter with Attractive Interactions
Exotic vortex states with long range attraction and short range repulsion
have recently been proposed to arise in superconducting hybrid structures and
multi-band superconductors. Using large scale simulations we examine the static
and dynamic properties of such vortex states interacting with random and
periodic pinning. In the absence of pinning this system does not form patterns
but instead completely phase separates. When pinning is present there is a
transition from inhomogeneous to homogeneous vortex configurations similar to a
wetting phenomenon. Under an applied drive, a dynamical dewetting process can
occur from a strongly pinned homogeneous state into pattern forming states. We
show that a signature of the exotic vortex interactions under transport
measurements is a robust double peak feature in the differential conductivity
curves.Comment: 5 pages, 4 postscript figure
Imaging characteristics and treatment of a penetrating brain injury caused by an oropharyngeal foreign body in a dog
A 4-year-old Border collie was presented with one episode of collapse, altered mentation, and a suspected pharyngeal stick injury. Magnetic resonance imaging (MRI) and computed tomography showed a linear foreign body penetrating the right oropharynx, through the foramen ovale and the brain parenchyma. The foreign body was surgically removed and medical treatment initiated. Complete resolution of clinical signs was noted at recheck 8 weeks later. Repeat MRI showed chronic secondary changes in the brain parenchyma. To the authors' knowledge, this is the first report of the advanced imaging findings and successful treatment of a penetrating oropharyngeal intracranial foreign body in a dog
A dynamical model of surrogate reactions
A new dynamical model is developed to describe the whole process of surrogate
reactions; transfer of several nucleons at an initial stage, thermal
equilibration of residues leading to washing out of shell effects and decay of
populated compound nuclei are treated in a unified framework. Multi-dimensional
Langevin equations are employed to describe time-evolution of collective
coordinates with a time-dependent potential energy surface corresponding to
different stages of surrogate reactions. The new model is capable of
calculating spin distributions of the compound nuclei, one of the most
important quantity in the surrogate technique. Furthermore, various observables
of surrogate reactions can be calculated, e.g., energy and angular distribution
of ejectile, and mass distributions of fission fragments. These features are
important to assess validity of the proposed model itself, to understand
mechanisms of the surrogate reactions and to determine unknown parameters of
the model. It is found that spin distributions of compound nuclei produced in
O+U O+U and O+U
O+U reactions are equivalent and much less than
10, therefore satisfy conditions proposed by Chiba and Iwamoto (PRC 81,
044604(2010)) if they are used as a pair in the surrogate ratio method.Comment: 17 pages, 5 figure
Baryonic Bound State of Vortices in Multicomponent Superconductors
We construct a bound state of three 1/3-quantized Josephson coupled vortices
in three-component superconductors with intrinsic Josephson couplings, which
may be relevant with regard to iron-based superconductors. We find a Y-shaped
junction of three domain walls connecting the three vortices, resembling the
baryonic bound state of three quarks in QCD. The appearance of the Y-junction
(but not a Delta-junction) implies that in both cases of superconductors and
QCD, the bound state is described by a genuine three-body interaction (but not
by the sum of two-body interactions). We also discuss a
confinement/deconfinement phase transition.Comment: 11 pages, 3 figures, one section on confinement/deconfinement
transition added, published versio
Naive Dimensional Analysis in Holography
Naive dimensional analysis (NDA) is a widely used ansatz to estimate coupling
constants among composite states emerging from dynamics of a strongly coupled
gauge theory. However, the validity of NDA is still unclear because of the
difficulty in calculating these quantities in strongly coupled theories. We
examine the NDA ansatz using gauge/string duality, by estimating glueball
coupling constants from gravitational description. The NDA scaling rule for
coupling constants of some types of glueballs is verified and extended by both
generic estimation and numerical calculations. The scaling rule verified in
this article can be applied to some class of quiver gauge theories as well, not
just to gauge theories with a single gauge group .Comment: 23 pages, 1 figur
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