11,084 research outputs found
Dynamical nucleus-nucleus potential at short distances
The dynamical nucleus-nucleus potentials for fusion reactions 40Ca+40Ca,
48Ca+208Pb and 126Sn+130Te are studied with the improved quantum molecular
dynamics (ImQMD) model together with the extended Thomas-Fermi approximation
for the kinetic energies of nuclei. The obtained fusion barrier for 40Ca+40Ca
is in good agreement with the extracted fusion barrier from the measured fusion
excitation function, and the depth of the fusion pockets are close to the
results of time-dependent Hartree-Fock calculations. The energy dependence of
fusion barrier is also investigated. For heavy fusion system, the fusion pocket
becomes shallow and almost disappears for symmetric systems and the obtained
potential at short distances is higher than the adiabatic potential.Comment: 6 figures, accepted for publication in Phys. Rev.
The Picard group of the loop space of the Riemann sphere
The loop space of the Riemann sphere consisting of all C^k or Sobolev W^{k,p}
maps from the circle S^1 to the sphere is an infinite dimensional complex
manifold. We compute the Picard group of holomorphic line bundles on this loop
space as an infinite dimensional complex Lie group with Lie algebra the first
Dolbeault group. The group of Mobius transformations G and its loop group LG
act on this loop space. We prove that an element of the Picard group is
LG-fixed if it is G-fixed; thus completely answer the question by Millson and
Zombro about G-equivariant projective embedding of the loop space of the
Riemann sphere.Comment: International Journal of Mathematic
Equivalence of glass transition and colloidal glass transition in the hard-sphere limit
We show that the slowing of the dynamics in simulations of several model
glass-forming liquids is equivalent to the hard-sphere glass transition in the
low-pressure limit. In this limit, we find universal behavior of the relaxation
time by collapsing molecular-dynamics data for all systems studied onto a
single curve as a function of , the ratio of the temperature to the
pressure. At higher pressures, there are deviations from this universal
behavior that depend on the inter-particle potential, implying that additional
physical processes must enter into the dynamics of glass-formation.Comment: 4 pages, 4 figure
Asteroseismology of KIC 8263801:Is it a member of NGC 6866 and a red clump star?
We present an asteroseismic analysis of the Kepler light curve of KIC
8263801, a red-giant star in the open cluster NGC 6866 that has previously been
reported to be a helium-burning red-clump star. We extracted the frequencies of
the radial and quadrupole modes from its frequency power spectrum and
determined its properties using a grid of evolutionary models constructed with
MESA. The oscillation frequencies were calculated using the GYRE code and the
surface term was corrected using the Ball & Gizon(2014) prescription. We find
that the star has a mass of , age Gyr and radius . By analyzing the internal
structure of the best-fitting model, we infer the evolutionary status of the
star KIC 8263801 as being on the ascending part of the red giant branch, and
not on the red clump. This result is verified using a purely asteroseismic
diagnostic, the diagram which can distinguish red
giant branch stars from red clump stars. Finally, by comparing its age with NGC
6866 ( Gyr) we conclude that KIC 8263801 is not a member of
this open cluster
Critical Phenomena and Thermodynamic Geometry of RN-AdS Black Holes
The phase transition of Reissner-Nordstr\"om black holes in
-dimensional anti-de Sitter spacetime is studied in details using the
thermodynamic analogy between a RN-AdS black hole and a van der Waals liquid
gas system. We first investigate critical phenomena of the RN-AdS black hole.
The critical exponents of relevant thermodynamical quantities are evaluated. We
find identical exponents for a RN-AdS black hole and a Van der Waals liquid gas
system. This suggests a possible universality in the phase transitions of these
systems. We finally study the thermodynamic behavior using the equilibrium
thermodynamic state space geometry and find that the scalar curvature diverges
exactly at the van der Waals-like critical point where the heat capacity at
constant charge of the black hole diverges.Comment: 18 pages, 5 figure
Generalized L\"uscher Formula in Multi-channel Baryon-Meson Scattering
L\"uscher's formula relates the elastic scattering phase shifts to the
two-particle energy levels in a finite cubic box. The original formula was
obtained for elastic scattering of two massive spinless particles in the center
of mass frame. In this paper, we consider the case for the scattering of a spin
1/2 particle with a spinless particle in multi-channel scattering. A
generalized relation between the energy of two particle system and the
scattering matrix elements is established. We first obtain this relation using
quantum-mechanics in both center-of-mass frame and in a general moving frame.
The result is then generalized to quantum field theory using methods outlined
in Ref. \cite{Hansen:2012tf}. We verify that the results obtained using both
methods are equivalent up to terms that are exponentially suppressed in the box
size.Comment: One reference adde
Adversarial Sparse-View CBCT Artifact Reduction
We present an effective post-processing method to reduce the artifacts from
sparsely reconstructed cone-beam CT (CBCT) images. The proposed method is based
on the state-of-the-art, image-to-image generative models with a perceptual
loss as regulation. Unlike the traditional CT artifact-reduction approaches,
our method is trained in an adversarial fashion that yields more perceptually
realistic outputs while preserving the anatomical structures. To address the
streak artifacts that are inherently local and appear across various scales, we
further propose a novel discriminator architecture based on feature pyramid
networks and a differentially modulated focus map to induce the adversarial
training. Our experimental results show that the proposed method can greatly
correct the cone-beam artifacts from clinical CBCT images reconstructed using
1/3 projections, and outperforms strong baseline methods both quantitatively
and qualitatively
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