55,164 research outputs found
Electric dipole response of He: Halo-neutron and core excitations
Electric dipole () response of He is studied with a fully
microscopic six-body calculation. The wave functions for the ground and excited
states are expressed as a superposition of explicitly correlated Gaussians
(CG). Final state interactions of three-body decay channels are explicitly
taken into account. The ground state properties and the low-energy
strength are obtained consistently with observations. Two main peaks as well as
several small peaks are found in the strength function. The peak at the
high-energy region indicates a typical macroscopic picture of the giant dipole
resonance, the out-of-phase proton-neutron motion. The transition densities of
the lower-lying peaks exhibit in-phase proton-neutron motion in the internal
region, out-of-phase motion near the surface region, and spatially extended
neutron oscillation, indicating a soft-dipole mode (SDM) and its vibrationally
excited mode.Comment: 12 pages, 12 figures, to appear in Phys. Rev.
Green's function method for strength function in three-body continuum
Practical methods to compute dipole strengths for a three-body system by
using a discretized continuum are analyzed. New techniques involving Green's
function are developed, either by correcting the tail of the approximate wave
function in a direct calculation of the strength function or by using a
solution of a driven Schroedinger equation in a summed expression of the
strength. They are compared with the complex scaling method and the Lorentz
integral transform, also making use of a discretized continuum. Numerical tests
are performed with a hyperscalar three-body potential in the
hyperspherical-harmonics formalism. They show that the Lorentz integral
transform method is less practical than the other methods because of a
difficult inverse transform. These other methods provide in general comparable
accuracies.Comment: 22 pages, 8 figures, to appear in Progress of Theoretical Physic
p-Wave superfluid and phase separation in atomic Bose-Fermi mixture
We consider a system of repulsively interacting Bose-Fermi mixtures of spin
polarized uniform atomic gases at zero temperature. We examine possible
realization of p-wave superfluidity of fermions due to an effective attractive
interaction via density fluctuations of Bose-Einstein condensate within
mean-field approximation. We find the ground state of the system by direct
energy comparison of p-wave superfluid and phase-separated states, and suggest
an occurrence of the p-wave superfluid for a strong boson-fermion interaction
regime. We study some signatures in the p-wave superfluid phase, such as
anisotropic energy gap and quasi-particle energy in the axial state, that have
not been observed in spin unpolarized superfluid of atomic fermions. We also
show that a Cooper pair is a tightly bound state like a diatomic molecule in
the strong boson-fermion coupling regime and suggest an observable indication
of the p-wave superfluid in the real experiment.Comment: 7 pages, 6 figur
Transverse momentum distribution with radial flow in relativistic diffusion model
Large transverse momentum distributions of identified particles observed at
RHIC are analyzed by a relativistic stochastic model in the three dimensional
(non-Euclidean) rapidity space. A distribution function obtained from the model
is Gaussian-like in radial rapidity. It can well describe observed transverse
momentum distributions. Estimation of radial flow is made from the
analysis of distributions for in Au + Au Collisions.
Temperatures are estimated from observed large distributions under the
assumption that the distribution function approaches to the Maxwell-Boltzmann
distribution in the lower momentum limit. Power-law behavior of large
distribution is also derived from the model.Comment: 7 pages, 5 figures and 6 table
Universal four-body states in heavy-light mixtures with positive scattering length
The number of four-body states known to behave universally is small. This
work adds a new class of four-body states to this relatively short list. We
predict the existence of a universal four-body bound state for heavy-light
mixtures consisting of three identical heavy fermions and a fourth
distinguishable lighter particle with mass ratio and
short-range interspecies interaction characterized by a positive s-wave
scattering length. The structural properties of these universal states are
discussed and finite-range effects are analyzed. The bound states can be
experimentally realized and probed utilizing ultracold atom mixtures.Comment: 5 page
Global-in-time behavior of the solution to a Gierer-Meinhardt system
Gierer-Meinhardt system is a mathematical model to describe biological pattern formation due to activator and inhibitor. Turing pattern is
expected in the presence of local self-enhancement and long-range inhibition.
The long-time behavior of the solution, however, has not yet been clarified mathematically. In this paper, we study the case when its ODE part takes
periodic-in-time solutions, that is, . Under some additional assumptions on parameters, we show that the solution exists global-in-time and absorbed into one of these ODE orbits. Thus spatial patterns eventually dis- appear if those parameters are in a region without local self-enhancement or long-range inhibition
Inelastic final-state interaction
The final-state interaction in multichannel decay processes is sytematically
studied with application to B decay in mind. Since the final-state inteaction
is intrinsically interwoven with the decay interaction in this case, no simple
phase theorem like "Watson's theorem" holds for experimentally observed final
states. We first examine in detail the two-channel problem as a toy-model to
clarify the issues and to remedy common mistakes made in earlier literature.
Realistic multichannel problems are too challenging for quantitative analysis.
To cope with mathematical complexity, we introduce a method of approximation
that is applicable to the case where one prominant inelastic channel dominates
over all others. We illustrate this approximation method in the amplitude of
the decay B to pi K fed by the intermediate states of a charmed meson pair.
Even with our approximation we need more accurate information of strong
interactions than we have now. Nonethless we are able to obtain some insight in
the issue and draw useful conclusions on general fearyres on the strong phases.Comment: The published version. One figure correcte
Three-body forces and shell structure in calcium isotopes
Understanding and predicting the formation of shell structure from nuclear
forces is a central challenge for nuclear physics. While the magic numbers
N=2,8,20 are generally well understood, N=28 is the first standard magic number
that is not reproduced in microscopic theories with two-nucleon forces. In this
Letter, we show that three-nucleon forces give rise to repulsive interactions
between two valence neutrons that are key to explain 48Ca as a magic nucleus,
with a high 2+ excitation energy and a concentrated magnetic dipole transition
strength. The repulsive three-nucleon mechanism improves the agreement with
experimental binding energies.Comment: 5 pages, 4 figures; improved version and added coupled-cluster
benchmark; published versio
- …