23,058 research outputs found
Gauge potential singularities and the gluon condensate at finite temperatures
The continuum limit of SU(2) lattice gauge theory is carefully investigated
at zero and at finite temperatures. It is found that the continuum gauge field
has singularities originating from center degrees of freedom being discovered
in Landau gauge. Our numerical results show that the density of these
singularities properly extrapolates to a non-vanishing continuum limit. The
action density of the non-trivial Z_2 links is tentatively identified with the
gluon condensate. We find for temperatures larger than the deconfinement
temperature that the thermal fluctuations of the embedded Z_2 gauge theory
result in an increase of the gluon condensate with increasing temperature.Comment: 3 pages, 2 figures, talk presented by K. Langfeld at the 19th
International Symposium on Lattice Field Theory (LATTICE2001), Berlin,
19.-24.8.2001, to appear in the proceeding
Magnetic Reynolds number dependence of reconnection rate and flow structure of the self-similar evolution model of fast magnetic reconnection
This paper investigates Magnetic Reynolds number dependence of the
``self-similar evolution model'' (Nitta et al. 2001) of fast magnetic
reconnection. I focused my attention on the flow structure inside and around
the reconnection outflow, which is essential to determine the entire
reconnection system (Nitta et al. 2002). The outflow is consist of several
regions divided by discontinuities, e.g., shocks, and it can be treated by a
shock-tube approximation (Nitta 2004). By solving the junction conditions
(e.g., Rankine-Hugoniot condition), the structure of the reconnection outflow
is obtained. Magnetic reconnection in most astrophysical problems is
characterized by a huge dynamic range of its expansion ( for typical
solar flares) in a free space which is free from any influence of external
circumstances. Such evolution results in a spontaneous self-similar expansion
which is controlled by two intrinsic parameters: the plasma- and the
magnetic Reynolds number. The plasma- dependence had been investigated in
our previous paper. This paper newly clarifies the relation between the
reconnection rate and the inflow structure just outside the Petschek-like slow
shock: As the magnetic Reynolds number increases, strongly converging inflow
toward the Petschek-like slow shock forms, and it significantly reduces the
reconnection rate.Comment: 16 pages. to appear in ApJ (2006 Jan. 20 issue
General relativistic effects on neutrino-driven wind from young, hot neutron star and the r-process nucleosynthesis
Neutrino-driven wind from young hot neutron star, which is formed by
supernova explosion, is the most promising candidate site for r-process
nucleosynthesis. We study general relativistic effects on this wind in
Schwarzschild geometry in order to look for suitable conditions for a
successful r-process nucleosynthesis. It is quantitatively discussed that the
general relativistic effects play a significant role in increasing entropy and
decreasing dynamic time scale of the neutrino-driven wind. Exploring wide
parameter region which determines the expansion dynamics of the wind, we find
interesting physical conditions which lead to successful r-process
nucleosynthesis. The conditions which we found realize in the neutrino-driven
wind with very short dynamic time scale ms and
relatively low entropy . We carry out the -process and
r-process nucleosynthesis calculation on these conditions by the use of our
single network code including over 3000 isotopes, and confirm quantitatively
that the second and third r-process abundance peaks are produced in the
neutrino-driven wind.Comment: Accepted for publication in Ap
Distribution of magnetic domain pinning fields in GaMnAs ferromagnetic films
Using the angular dependence of the planar Hall effect in GaMnAs
ferromagnetic films, we were able to determine the distribution of magnetic
domain pinning fields in this material. Interestingly, there is a major
difference between the pinning field distribution in as-grown and in annealed
films, the former showing a strikingly narrower distribution than the latter.
This conspicuous difference can be attributed to the degree of non-uniformity
of magnetic anisotropy in both types of films. This finding provides a better
understanding of the magnetic domain landscape in GaMnAs that has been the
subject of intense debate
Iron-Based Heavy Quasiparticles in SrFeSb: An Infrared Spectroscopic Study
Temperature-dependent infrared reflectivity spectra of SrFeSb
has been measured. A renormalized Drude peak with a heavy effective mass and a
pronounced pseudogap of 10 meV develops in the optical conductivity spectra at
low temperatures. As the temperature decreases below 100 K, the effective mass
() rapidly increases, and the scattering rate () is quenched.
The temperature dependence of and indicates that the
hybridization between the Fe 3d spins and the charge carriers plays an
important role in determining the physical properties of SrFeSb at
low temperatures. This result is the clear evidence of the iron-based heavy
quasiparticles.Comment: 5 pages, 5 figure
Walls in supersymmetric massive nonlinear sigma model on complex quadric surface
The Bogomol'nyi-Prasad-Sommerfield (BPS) multiwall solutions are constructed
in a massive Kahler nonlinear sigma model on the complex quadric surface,
Q^N=SO(N+2)/[SO(N)\times SO(2)] in 3-dimensional space-time. The theory has a
non-trivial scalar potential generated by the Scherk-Schwarz dimensional
reduction from the massless nonlinear sigma model on Q^N in 4-dimensional
space-time and it gives rise to 2[N/2+1] discrete vacua. The BPS wall solutions
connecting these vacua are obtained based on the moduli matrix approach. It is
also shown that the moduli space of the BPS wall solutions is the complex
quadric surface Q^N.Comment: 42 pages, 30 figures, typos corrected, version to appear in PR
Z' from SU(6)SU(2)_h GUT, Wjj anomaly and Higgs boson mass bound
A general electroweak scale is applied in a supersymmetric
SU(6)\timesSU(2)_h grand unification model, to have a for the
hexality. We briefly show that there cannot exist any baryonic U(1) in any
subgroup of E. Any effect that requires sizable couplings to quarks
like the reported Wjj anomaly of CDF, if observed, implies a substantial
coupling to leptons or Higgs doublets. The kinetic mixing considered in a
supersymmetric model from E is restricted by the gauge coupling unification
and neutrino mixing. The mass of is strongly constrained by the
electroweak parameter. We conclude that mass much above 10 TeV is
favored by considering the neutrino mixing and proton decay constraint in
supersymmetric models. In this sense, the CDF anomaly cannot be fitted to
any electroweak model descending from E. Furthermore, if is found at
several hundred GeV, any grand unification group embedded in E such as
SU(6)SU(2), SO(10), SU(5)U(1), SU(5), SU(4)SU(4), and
SU(3), needs fine-tuned gauge couplings. We also discuss the U(1) effect
on the tree level mass of the lightest MSSM Higgs boson.Comment: 1 figure, 6 page
Lithium production on a low-mass secondary in a black hole soft X-ray transient
We examine production of Li on the surface of a low-mass secondary in a black
hole soft X-ray transient (BHSXT) through the spallation of CNO nuclei by
neutrons which are ejected from a hot (> 10 MeV) advection-dominated accretion
flow (ADAF) around the black hole. Using updated binary parameters, cross
sections of neutron-induced spallation reactions, and mass accretion rates in
ADAF derived from the spectrum fitting of multi-wavelength observations of
quiescent BHSXTs, we obtain the equilibrium abundances of Li by equating the
production rate of Li and the mass transfer rate through accretion to the black
hole. The resulting abundances are found to be in good agreement with the
observed values in seven BHSXTs. We note that the abundances vary in a
timescale longer than a few months in our model. Moreover, the isotopic ratio
Li6/Li7 is calculated to be about 0.7--0.8 on the secondaries, which is much
higher than the ratio measured in meteorites. Detection of such a high value is
favorable to the production of Li via spallation and the existence of a hot
accretion flow, rather than an accretion disk corona system in quiescent BHSXT.Comment: 4 pages, 3 figures, and 2 tables, submitted to Astrophyscal Jounal
Letter
Probabilistic cash flow-based optimal investment timing using two-color rainbow options valuation for economic sustainability appraisement
This research determines the optimal investment timing using real options valuation to support decision-making for economic sustainability assessment. This paper illustrates an option pricing model using the Black-Scholes model applied to a case project to understand the model performance. Applicability of the project to the model requires two Monte Carlo simulations to satisfy a Markov process and a Wiener process. The position of project developers is not only the seller of products, but it is also the buyer of raw materials. Real options valuation can be influenced by the volatility of cash outflow, as well as the volatility of cash inflow. This study suggests two-color rainbow options valuation to overcome this issue, which is demonstrated for a steel plant project. The asymmetric results of the case study show that cash outflow (put option) influences the value of the steel plant project more than cash inflow (call option) does of which the discussion of the results is referred to a sensitivity analysis. The real options valuation method proposed in this study contributes to the literature on applying the new model, taking into consideration that investors maximize project profitability for economic sustainable development. ? 2017 by the authors.111sciessciscopu
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