A new screening function for Coulomb renormalization

We introduce a new screening function which is useful for the few-body Coulomb scattering problem in ``screening and renormalization'' scheme. The new renormalization phase factor of the screening function is analytically shown. The Yukawa type of the screening potential has been used in several decades, we modify it to make more useful. As a concrete example, we compare the proton-proton scattering phase shifts calculated from these potentials. The numerical results document that high precision calculations of the renormalization are performed by the new screening function.Comment: 4 pages, 8 figure

Cooling of a Micro-mechanical Resonator by the Back-action of Lorentz Force

Using a semi-classical approach, we describe an on-chip cooling protocol for a micro-mechanical resonator by employing a superconducting flux qubit. A Lorentz force, generated by the passive back-action of the resonator's displacement, can cool down the thermal motion of the mechanical resonator by applying an appropriate microwave drive to the qubit. We show that this onchip cooling protocol, with well-controlled cooling power and a tunable response time of passive back-action, can be highly efficient. With feasible experimental parameters, the effective mode temperature of a resonator could be cooled down by several orders of magnitude.Comment: 10 pages, 4 figure

Creep rupture of materials: insights from a fiber bundle model with relaxation

I adapted a model recently introduced in the context of seismic phenomena, to study creep rupture of materials. It consists of linear elastic fibers that interact in an equal load sharing scheme, complemented with a local viscoelastic relaxation mechanism. The model correctly describes the three stages of the creep process, namely an initial Andrade regime of creep relaxation, an intermediate regime of rather constant creep rate, and a tertiary regime of accelerated creep towards final failure of the sample. In the tertiary regime creep rate follows the experimentally observed one over time-to-failure dependence. The time of minimum strain rate is systematically observed to be about 60-65 % of the time to failure, in accordance with experimental observations. In addition, burst size statistics of breaking events display a -3/2 power law for events close to the time of failure, and a steeper decay for the all-time distribution. Statistics of interevent times shows a tendency of the events to cluster temporarily. This behavior should be observable in acoustic emission experiments

Electroweak Baryogenesis with Embedded Domain Walls

We consider electroweak baryogenesis mediated by embedded domain walls. Embedded domain walls originating from a symmetry breaking phase transition are stabilized by thermal plasma effects, so that the electroweak symmetry is unbroken in their cores. For this reason, the cosmological evolution of such domain walls can generate a sufficiently large baryon asymmetry, irrespective of the order of the electroweak phase transition. For embedded domain walls, the condition that the energy of the universe not be dominated by the energy of the domain walls is relaxed significantly, and it is shown to be compatible with our scenario of electroweak baryogenesis.Comment: 12 pages, no figur

Note on the Robustness of the Neutrino Mass Bounds from Cosmology

The recent high precision maps of cosmic microwave anisotropies combined with measurements of the galaxy power spectrum from new large-scale redshift surveys have allowed stringent bounds on the sum of the neutrino masses to be placed. The past analyses, however, have implicitly assumed that the spectrum of primordial density fluctuations is adiabatic and coherent, as predicted in the simplest models of inflation. In this paper, we show that the limits hold even if the assumption on the primordial power spectrum is relaxed to allow for a contribution of nonadiabatic, incoherent fluctuations such as would be predicted by topological defects.Comment: 4 pages, to appear in Phys. Rev. D (R

Spin Fluid Dynamics Observed by Magnetic Fountain Effect and Mechano-Spin Effect in the Ferromagnetic Superfluid 3^3He A1_1 Phase

Systematic observations of the magnetically generated fountain pressure in the superfluid $^3$He A$_1$ have been carried out in a newly built apparatus designed to reduce the effect of thermal gradients. In the same apparatus, mechanical pumping and filtering of polarized nuclear spins were realized by the pneumatic pumping action of an electrostatically actuated membrane. In both experiments, the measured induced pressure was observed to decay at all temperatures where the A$_1$ phase appeared in magnetic fields up to 13 T and liquid pressures between 1 and 29 bar. The inferred spin relaxation rate tended to increase as the low temperature phase boundary with the A$_2$ phase (T$_{C2}$) was approached. The increase in spin relaxation rate near T$_{C2}$ can be explained by the presence of a minority spin condensate in the A$_1$ phase as predicted by Monien and Tewordt and by the application of the Leggett-Takagi theory of spin relaxation in superfluid $^3$He.Comment: 12 pages, 15 figures, to appear in Physical Review