2,194 research outputs found
Scalar and vector meson exchange in V->P0P0gamma decays
The scalar contributions to the radiative decays of light vector mesons into
a pair of neutral pseudoscalars, , are studied within the
framework of the Linear Sigma Model. This model has the advantage of
incorporating not only the scalar resonances in an explicit way but also the
constraints required by chiral symmetry. The experimental data on
, ,
and are satisfactorily accommodated in our
framework. Theoretical predictions for ,
, and the ratio are also given.Comment: 42 pages, 11 figures. A new paragraph explaining the seminal
contribution of Ref. [19] is adde
Measuring spectrum of spin wave using vortex dynamics
We propose to measure the spectrum of magnetic excitation in magnetic
materials using motion of vortex lattice driven by both ac and dc current in
superconductors. When the motion of vortex lattice is resonant with oscillation
of magnetic moments, the voltage decreases at a given current. From transport
measurement, one can obtain frequency of the magnetic excitation with the wave
number determined by vortex lattice constant. By changing the lattice constant
through applied magnetic fields, one can obtains the spectrum of the magnetic
excitation up to a wave vector of order .Comment: 4 pages, 2 figure
Extremely Large and Anisotropic Upper Critical Field and the Ferromagnetic Instability in UCoGe
Magnetoresistivity measurements with fine tuning of the field direction on
high quality single crystals of the ferromagnetic superconductor UCoGe show
anomalous anisotropy of the upper critical field H_c2. H_c2 for H // b-axis
(H_c2^b) in the orthorhombic crystal structure is strongly enhanced with
decreasing temperature with an S-shape and reaches nearly 20 T at 0 K. The
temperature dependence of H_c2^a shows upward curvature with a low temperature
value exceeding 30 T, while H_c2^c at 0 K is very small (~ 0.6 T). Contrary to
conventional ferromagnets, the decrease of the Curie temperature with
increasing field for H // b-axis marked by an enhancement of the effective mass
of the conduction electrons appears to be the origin of the S-shaped H_c2^b
curve. These results indicate that the field-induced ferromagnetic instability
or magnetic quantum criticality reinforces superconductivity.Comment: 5 pages, 4 figures, accepted for publication in J. Phys. Soc. Jp
Area Distribution of Elastic Brownian Motion
We calculate the excursion and meander area distributions of the elastic
Brownian motion by using the self adjoint extension of the Hamiltonian of the
free quantum particle on the half line. We also give some comments on the area
of the Brownian motion bridge on the real line with the origin removed. We will
stress on the power of self adjoint extension to investigate different possible
boundary conditions for the stochastic processes.Comment: 18 pages, published versio
Quantum Free Yang-Mills on the Plane
We construct a free-probability quantum Yang-Mills theory on the two
dimensional plane, determine the Wilson loop expectation values, and show that
this theory is the limit of U(N) quantum Yang-Mills theory on the
plane.Comment: 24 pages, tikz figure
Influence of deposition parameters on mechanical properties of sputter-deposited Cr2O3 thin films
Among the oxides, Cr2O3 exhibits the highest hardness value and a low coefficient of friction. These properties make chromium oxide an excellent coating material for tribological applications. Cr2O3 thin films were deposited by radio-frequency reactive magnetron sputtering at substrate temperature in the range 363-593 K. The hardness and elastic modulus of the films were measured by two complementary nanoindentation techniques to investigate the influences of the substrate temperature and the oxygen content in the sputtering gas. While the continuous stiffness data method provides information throughout the whole film thickness, nanoindentation combined with scanning force microscopy of the residual imprints allows visualization of pileup, cracking, and delamination from the substrate. Hardness values up to 32 GPa were obtained for substrate temperatures exceeding 500 K and oxygen contents between 15% and 25% of the total gas pressure. The films, obtained with these deposition conditions, showed good adhesion to silicon substrate
Pressure Evolution of the Ferromagnetic and Field Re-entrant Superconductivity in URhGe
Fine pressure () and magnetic field () tuning on the ferromagnetic
superconductor URhGe are reported in order to clarify the interplay between the
mass enhancement, low field superconductivity (SC) and field reentrant
superconductivity (RSC) by electrical resistivity measurements. With increasing
, the transition temperature and the upper critical field of the low field
SC decrease slightly, while the RSC dome drastically shifts to higher fields
and shrinks. The spin reorientation field also increases. At a
pressure GPa, the RSC has collapsed while the low field SC persists
and may disappear only above 4 GPa. Via careful studies of the
inelastic resistivity term, it is demonstrated that this drastic change
is directly related with the dependence of the effective mass which
determines the critical field of the low field SC and RSC on the basis of
triplet SC without Pauli limiting field.Comment: 5 pages, 6 figures, to appear in Journal of the Physical Society of
Japa
Fostering collective intelligence education
New educational models are necessary to update learning environments to the digitally shared communication and information. Collective intelligence is an emerging field that already has a significant impact in many areas and will have great implications in education, not only from the side of new methodologies but also as a challenge for education. This paper proposes an approach to a collective intelligence model of teaching using Internet to combine two strategies: idea management and real time assessment in the class. A digital tool named Fabricius has been created supporting these two elements to foster the collaboration and engagement of students in the learning process. As a result of the research we propose a list of KPI trying to measure individual and collective performance. We are conscious that this is just a first approach to define which aspects of a class following a course can be qualified and quantified.Postprint (published version
Spectral statistics of disordered metals in the presence of several Aharonov-Bohm fluxes
The form factor for spectral correlations in a diffusive metal is calculated
in the presence of several Aharonov-Bohm fluxes. When the fluxes are
equal, the correlations are universal functions of where is
the dimensionless conductance and is the number of applied fluxes. This
explains recent flux dependence of the correlations found numerically at the
metal-insulator transition.Comment: 3 pages, Latex, 1 figure, to appear in Phys. Rev. B Rapid Com
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