5,238 research outputs found
Modified Reconstruction of Standard Model in Non-Commutative Differential Geometry
Sogami recently proposed the new idea to express Higgs particle as a kind of
gauge particle by prescribing the generalized covariant derivative with gauge
and Higgs fields operating on quark and lepton fields. The field strengths for
both the gauge and Higgs fields are defined by the commutators of the covariant
derivative by which he could obtain the Yang-Mills Higgs Lagrangian in the
standard model. Inspired by Sogami's work, we present a modification of our
previous scheme to formulate the spontaneously broken gauge theory in
non-commutative geometry on the discrete space; Minkowski space multiplied by
two points space by introducing the generation mixing matrix in operation of
the generalized derivative on the more fundamental fields a_i(x,y) which
compose the gauge and Higgs fields. The standard model is reconstructed
according to the modified scheme, which does not yields not only any special
relations between the particle masses but also the special restriction on the
Higgs potential.Comment: 21 page
BRST invariant Lagrangian of spontaneously broken gauge theories in noncommutative geometry
The quantization of spontaneously broken gauge theories in noncommutative
geometry(NCG) has been sought for some time, because quantization is crucial
for making the NCG approach a reliable and physically acceptable theory. Lee,
Hwang and Ne'eman recently succeeded in realizing the BRST quantization of
gauge theories in NCG in the matrix derivative approach proposed by Coquereaux
et al. The present author has proposed a characteristic formulation to
reconstruct a gauge theory in NCG on the discrete space .
Since this formulation is a generalization of the differential geometry on the
ordinary manifold to that on the discrete manifold, it is more familiar than
other approaches. In this paper, we show that within our formulation we can
obtain the BRST invariant Lagrangian in the same way as Lee, Hwang and Ne'eman
and apply it to the SU(2)U(1) gauge theory.Comment: RevTeX, page
Calculations of Branching Ratios for Radiative-Capture, One-Proton, and Two-Neutron Channels in the Fusion Reaction Bi+Zn
We discuss the possibility of the non-one-neutron emission channels in the
cold fusion reaction Zn + Bi to produce the element Z=113. For
this purpose, we calculate the evaporation-residue cross sections of
one-proton, radiative-capture, and two-neutron emissions relative to the
one-neutron emission in the reaction Zn + Bi. To estimate the
upper bounds of those quantities, we vary model parameters in the calculations,
such as the level-density parameter and the height of the fission barrier. We
conclude that the highest possibility is for the 2n reaction channel, and its
upper bounds are 2.4 and at most less than 7.9% with unrealistic parameter
values, under the actual experimental conditions of [J. Phys. Soc. Jpn. {\bf
73} (2004) 2593].Comment: 6 pages, 4 figure
Field Theory in Noncommutative Minkowski Superspace
There is much discussion of scenarios where the space-time coordinates x^\mu
are noncommutative. The discussion has been extended to include nontrivial
anticommutation relations among spinor coordinates in superspace. A number of
authors have studied field theoretical consequences of the deformation of N=1
superspace arising from nonanticommutativity of coordinates \theta, while
leaving \bar{theta}'s anticommuting. This is possible in Euclidean superspace
only. In this note we present a way to extend the discussion by making both
\theta and \bar{theta} coordinates non-anticommuting in Minkowski superspace.
We present a consistent algebra for the supercoordinates, find a star-product,
and give the Wess-Zumino Lagrangian L_{WZ} within our model. It has two extra
terms due to non(anti)commutativity. The Lagrangian in Minkowski superspace is
always manifestly Hermitian and for L_{WZ} it preserves Lorentz invariance.Comment: 8 pages, added references, two-column format, published in PR
ALMA Temporal Phase Stability and the Effectiveness of Water Vapor Radiometer
Atacama Large Millimeter/submillimeter Array (ALMA) will be the world largest
mm/submm interferometer, and currently the Early Science is ongoing, together
with the commissioning and science verification (CSV). Here we present a study
of the temporal phase stability of the entire ALMA system from antennas to the
correlator. We verified the temporal phase stability of ALMA using data, taken
during the last two years of CSV activities. The data consist of integrations
on strong point sources (i.e., bright quasars) at various frequency bands, and
at various baseline lengths (up to 600 m). From the observations of strong
quasars for a long time (from a few tens of minutes, up to an hour), we derived
the 2-point Allan Standard Deviation after the atmospheric phase correction
using the 183 GHz Water Vapor Radiometer (WVR) installed in each 12 m antenna,
and confirmed that the phase stability of all the baselines reached the ALMA
specification. Since we applied the WVR phase correction to all the data
mentioned above, we also studied the effectiveness of the WVR phase correction
at various frequencies, baseline lengths, and weather conditions. The phase
stability often improves a factor of 2 - 3 after the correction, and sometimes
a factor of 7 improvement can be obtained. However, the corrected data still
displays an increasing phase fluctuation as a function of baseline length,
suggesting that the dry component (e.g., N2 and O2) in the atmosphere also
contributes the phase fluctuation in the data, although the imperfection of the
WVR phase correction cannot be ruled out at this moment.Comment: Proc. SPIE 8444-125, in press (7 pages, 4 figures, 1 table
Low-lying excitations around a single vortex in a d-wave superconductor
A full quantum-mechanical treatment of the Bogoliubov-de Gennes equation for
a single vortex in a d-wave superconductor is presented. First, we find
low-energy states extended in four diagonal directions, which have no
counterpart in a vortex of s-wave superconductors. The four-fold symmetry is
due to 'quantum effect', which is enhanced when is small. Second,
for , a peak with a large energy gap is
found in the density of states, which is due to the formation of the lowest
bound states.Comment: 7pages, Revte
Homogeneous bubble nucleation limit of mercury under the normal working conditions of the planned European Spallation Source
In spallation neutron sources, liquid mercury is the subject of big thermal
and pressure shocks, upon adsorbing the proton beam. These changes can cause
unstable bubbles in the liquid, which can damage the structural material. While
there are methods to deal with the pressure shock, the local temperature shock
cannot be avoided. In our paper we calculated the work of the critical cluster
formation (i.e. for mercury micro-bubbles) together with the rate of their
formation (nucleation rate). It is shown that the homogeneous nucleation rates
are very low even after adsorbing several proton pulses, therefore the
probability of temperature induced homogeneous bubble nucleation is negligible.Comment: 22 Pages, 11 figures, one of them is colour, we plan to publish it in
Eur. Phys. J.
Alpha-decay properties of superheavy elements in the relativistic mean-field theory with vector self-coupling of meson
We have investigated properties of -decay chains of recently produced
superheavy elements Z=115 and Z=113 using the new Lagrangian model NL-SV1 with
inclusion of the vector self-coupling of meson in the framework of the
relativistic mean-field theory. It is shown that the experimentally observed
alpha-decay energies and half-lives are reproduced well by this Lagrangian
model. Further calculations for the heavier elements with Z=117-125 show that
these nuclei are superdeformed with a prolate shape in the ground state. A
superdeformed shell-closure at Z=118 lends an additional binding and an extra
stability to nuclei in this region. Consequently, it is predicted that the
corresponding values provide -decay half-lives for heavier
superheavy nuclei within the experimentally feasible conditions. The results
are compared with those of macroscopic-microscopic approaches. A perspective of
the difference in shell effects amongst various approaches is presented and its
consequences on superheavy nuclei are discussed.Comment: Revised version, 14 pages, 12 eps figures. To appear in PRC.
Discussion on shell effects is shortened in the revised version. However,
commonality of the role of shell effects in extreme superheavy regions and in
the regions near the r-process path is maintained. Existence of a secondary
superdeformed minimum for Z=113 is verified with another Lagrangian se
Novel vortex lattice transition in d-wave superconductors
We study the vortex state in a magnetic field parallel to the axis in the
framework of the extended Ginzburg Landau equation. We find the vortex acquires
a fourfold modulation proportional to where is the angle
makes with the -axis. This term gives rise to an attractive
interaction between two vortices when they are aligned parallel to or
. We predict the first order vortex lattice transition at
from triangular into the square lattice
tilted by from the axis. This gives the critical field
a few Tesla for YBCO and Bi2212 monocrystals at low temperatures ().Comment: 6 pages, 4 figure
Future of superheavy element research: Which nuclei could be synthesized within the next few years?
Low values of the fusion cross sections and very short half-lives of nuclei
with Z120 put obstacles in synthesis of new elements. Different nuclear
reactions (fusion of stable and radioactive nuclei, multi-nucleon transfers and
neutron capture), which could be used for the production of new isotopes of
superheavy (SH) elements, are discussed in the paper. The gap of unknown SH
nuclei, located between the isotopes which were produced earlier in the cold
and hot fusion reactions, can be filled in fusion reactions of Ca with
available lighter isotopes of Pu, Am, and Cm. Cross sections for the production
of these nuclei are predicted to be rather large, and the corresponding
experiments can be easily performed at existing facilities. For the first time,
a narrow pathway is found to the middle of the island of stability owing to
possible -decay of SH isotopes which can be formed in ordinary fusion
reactions of stable nuclei. Multi-nucleon transfer processes at near barrier
collisions of heavy (and very heavy, U-like) ions are shown to be quite
realistic reaction mechanism allowing us to produce new neutron enriched heavy
nuclei located in the unexplored upper part of the nuclear map. Neutron capture
reactions can be also used for the production of the long-living neutron rich
SH nuclei. Strong neutron fluxes might be provided by pulsed nuclear reactors
and by nuclear explosions in laboratory conditions and by supernova explosions
in nature. All these possibilities are discussed in the paper.Comment: An Invited Plenary Talk given by Valeriy I. Zagrebaev at the 11th
International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio,
Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in
Journal of Physics: Conference Series (JPCS
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