7,266 research outputs found
3-D unrestricted TDHF fusion calculations using the full Skyrme interaction
We present a study of fusion cross sections using a new generation
Time-Dependent Hartree-Fock (TDHF) code which contains no approximations
regarding collision geometry and uses the full Skyrme interaction, including
all of the time-odd terms. In addition, the code uses the Basis-Spline
collocation method for improved numerical accuracy. A comparative study of
fusion cross sections for is made with the older TDHF
results and experiments. We present results using the modern Skyrme forces and
discuss the influence of the new terms present in the interaction.Comment: 7 pages, 10 figure
The Casimir Energy for a Hyperboloid Facing a Plate in the Optical Approximation
We study the Casimir energy of a massless scalar field that obeys Dirichlet
boundary conditions on a hyperboloid facing a plate. We use the optical
approximation including the first six reflections and compare the results with
the predictions of the proximity force approximation and the semi-classical
method. We also consider finite size effects by contrasting the infinite with a
finite plate. We find sizable and qualitative differences between the new
optical method and the more traditional approaches.Comment: v2: 14 pages, 11 eps figures; typo in eq. (21) removed, clarification
added, fig. 10 improved; version published in Phys. Rev.
Chiral corrections to the isovector double scattering term for the pion-deuteron scattering length
The empirical value of the real part of the pion-deuteron scattering length
can be well understood in terms of the dominant isovector -double
scattering contribution. We calculate in chiral perturbation theory all
one-pion loop corrections to this double scattering term which in the case of
-scattering close the gap between the current-algebra prediction and the
empirical value of the isovector threshold T-matrix . In addition
to closing this gap there is in the -system a loop-induced off-shell
correction for the exchanged virtual pion. Its coordinate space representation
reveals that it is equivalent to -exchange in the deuteron. We evaluate
the chirally corrected double scattering term and the off-shell contribution
with various realistic deuteron wave functions. We find that the off-shell
correction contributes at most -8% and that the isovector double scattering
term explains at least 90% of the empirical value of the real part of the -scattering length.Comment: 4 pages, 2 figures, to be published in The Physical Review
Computability of the Radon-Nikodym derivative
We study the computational content of the Radon-Nokodym theorem from measure
theory in the framework of the representation approach to computable analysis.
We define computable measurable spaces and canonical representations of the
measures and the integrable functions on such spaces. For functions f,g on
represented sets, f is W-reducible to g if f can be computed by applying the
function g at most once. Let RN be the Radon-Nikodym operator on the space
under consideration and let EC be the non-computable operator mapping every
enumeration of a set of natural numbers to its characteristic function. We
prove that for every computable measurable space, RN is W-reducible to EC, and
we construct a computable measurable space for which EC is W-reducible to RN
Multisystem proteinopathy due to a homozygous p.Arg159His VCP mutation : a tale of the unexpected
ObjectiveTo assess the clinical, radiologic, myopathologic, and proteomic findings in a patient manifesting a multisystem proteinopathy due to a homozygous valosin-containing protein gene (VCP) mutation previously reported to be pathogenic in the heterozygous state.MethodsWe studied a 36-year-old male index patient and his father, both presenting with progressive limb-girdle weakness. Muscle involvement was assessed by MRI and muscle biopsies. We performed whole-exome sequencing and Sanger sequencing for segregation analysis of the identified p.Arg159His VCP mutation. To dissect biological disease signatures, we applied state-of-the-art quantitative proteomics on muscle tissue of the index case, his father, 3 additional patients with VCP-related myopathy, and 3 control individuals.ResultsThe index patient, homozygous for the known p.Arg159His mutation in VCP, manifested a typical VCP-related myopathy phenotype, although with a markedly high creatine kinase value and a relatively early disease onset, and Paget disease of bone. The father exhibited a myopathy phenotype and discrete parkinsonism, and multiple deceased family members on the maternal side of the pedigree displayed a dementia, parkinsonism, or myopathy phenotype. Bioinformatic analysis of quantitative proteomic data revealed the degenerative nature of the disease, with evidence suggesting selective failure of muscle regeneration and stress granule dyshomeostasis.ConclusionWe report a patient showing a multisystem proteinopathy due to a homozygous VCP mutation. The patient manifests a severe phenotype, yet fundamental disease characteristics are preserved. Proteomic findings provide further insights into VCP-related pathomechanisms
Quark-antiquark potential with retardation and radiative contributions and the heavy quarkonium mass spectra
The charmonium and bottomonium mass spectra are calculated with the
systematic account of all relativistic corrections of order v^2/c^2 and the
one-loop radiative corrections. Special attention is paid to the contribution
of the retardation effects to the spin-independent part of the quark-antiquark
potential, and a general approach to accounting for retardation effects in the
long-range (confining) part of the potential is presented. A good fit to
available experimental data on the mass spectra is obtained.Comment: 20 pages, revtex, 2 Postscript figure
Local Anisotropy of Fluids using Minkowski Tensors
Statistics of the free volume available to individual particles have
previously been studied for simple and complex fluids, granular matter,
amorphous solids, and structural glasses. Minkowski tensors provide a set of
shape measures that are based on strong mathematical theorems and easily
computed for polygonal and polyhedral bodies such as free volume cells (Voronoi
cells). They characterize the local structure beyond the two-point correlation
function and are suitable to define indices of
local anisotropy. Here, we analyze the statistics of Minkowski tensors for
configurations of simple liquid models, including the ideal gas (Poisson point
process), the hard disks and hard spheres ensemble, and the Lennard-Jones
fluid. We show that Minkowski tensors provide a robust characterization of
local anisotropy, which ranges from for vapor
phases to for ordered solids. We find that for fluids,
local anisotropy decreases monotonously with increasing free volume and
randomness of particle positions. Furthermore, the local anisotropy indices
are sensitive to structural transitions in these simple
fluids, as has been previously shown in granular systems for the transition
from loose to jammed bead packs
Towards exotic nuclei via binary reaction mechanism
Assuming a binary reaction mechanism, the yield of isotopes near the heaviest
neutron-deficit nucleus Sn is studied with a microscopic
transport model. The large influence of nuclear shell structure and isotope
composition of the colliding nuclei on the production of exotic nuclei is
demonstrated. It is shown that the reaction Fe+Cd seems to be
most favourable for producing primary exotic Sn isotopes which may survive if
the excitation energy in the entrance reaction channel is less than about 100
MeV. In the case of large differences in the charge (mass) numbers between
entrance and exit channels the light fragment yield is essentially fed from the
decay of excited primary heavier fragments. The existence of optimal energies
for the production of some oxygen isotopes in the binary mechanism is
demonstrated for the S+Au reaction.Comment: 17 pages, RevTex, 8 Postscript figures, submitted to Phys. Rev.
Large orders in strong-field QED
We address the issue of large-order expansions in strong-field QED. Our
approach is based on the one-loop effective action encoded in the associated
photon polarisation tensor. We concentrate on the simple case of crossed fields
aiming at possible applications of high-power lasers to measure vacuum
birefringence. A simple next-to-leading order derivative expansion reveals that
the indices of refraction increase with frequency. This signals normal
dispersion in the small-frequency regime where the derivative expansion makes
sense. To gain information beyond that regime we determine the factorial growth
of the derivative expansion coefficients evaluating the first 80 orders by
means of computer algebra. From this we can infer a nonperturbative imaginary
part for the indices of refraction indicating absorption (pair production) as
soon as energy and intensity become (super)critical. These results compare
favourably with an analytic evaluation of the polarisation tensor asymptotics.
Kramers-Kronig relations finally allow for a nonperturbative definition of the
real parts as well and show that absorption goes hand in hand with anomalous
dispersion for sufficiently large frequencies and fields.Comment: 26 pages, 6 figure
- …