505 research outputs found
Thermal Restoration of Chiral Symmetry in Supersymmetric Nambu-Jona-Lasinio Model with Soft SUSY Breaking
The supersymmetric version of the Nambu-Jona-Lasinio model is investigated in
connection with the chiral symmetry breaking induced by a soft SUSY breaking
term. It is found that the broken chiral symmetry due to the soft breaking term
is restored at suitably high temperature and the symmetry restoration occurs as
first-order phase transitions. The critical temperature at which the chiral
symmetry is restored is determined as a function of the strength of the soft
breaking term and the field coupling constant. The dynamical fermion mass is
calculated at finite temperature. Some possible applications to the breaking
scenario of unified field theories are discussed.Comment: 9 pages, 2 figure
Pattern of Chiral Symmetry Restoration at Finite Temperature in A Supersymmetric Composite Model
The structure of chiral symmetry restorations at finite temperature is
thoroughly investigated in the supersymmetric Nambu-Jona-Lasinio model with a
soft supersymmetry breaking term. It is found that the broken chiral symmetry
at vanishing temperature is restored at sufficiently high temperature in two
patterns, i. e., the first order and second order phase transition depending on
the choice of the coupling constant and the supersymmetry breaking
parameter . The critical curves expressing the phase boundaries in the
plane are completely determined and the dynamically generated
fermion mass is calculated as a function of temperature.Comment: 12 pages, 4 figures, REVTe
Path-Integral Formulation of Casimir Effects in Supersymmetric Quantum Electrodynamics
The Casimir effect is an interesting phenomenon in the sense that it provides
us with one of the primitive means of extracting the energy out of the vacuum.
Since the original work of Casimir a number of works have appeared in extending
the result to the case of more general topological and dynamical configurations
of the boundary condition and to the circumstances at finite temperature and
gravity. In the studies of the Casimir effects it is common to assume the free
electromagnetic field in the bounded region. It may be interesting to extend
our arguments for fields other than the electromagnetic field. The Casimir
effect due to the free fermionic fields has been investigated by several
authors and has been found to result in an attractive force under the suitable
physical boundary conditions.Comment: 12 pages, 6 figures, REVTe
Curvature-induced phase transitions in the inflationary universe - Supersymmetric Nambu-Jona-Lasinio Model in de Sitter spacetime -
The phase structure associated with the chiral symmetry is thoroughly
investigated in de Sitter spacetime in the supersymmetric Nambu-Jona-Lasinio
model with supersymmetry breaking terms. The argument is given in the three and
four space-time dimensions in the leading order of the 1/N expansion and it is
shown that the phase characteristics of the chiral symmetry is determined by
the curvature of de Sitter spacetime. It is found that the symmetry breaking
takes place as the first order as well as second order phase transition
depending on the choice of the coupling constant and the parameter associated
with the supersymmetry breaking term. The critical curves expressing the phase
boundary are obtained. We also discuss the model in the context of the chaotic
inflation scenario where topological defects (cosmic strings) develop during
the inflation.Comment: 29 pages, 6 figures, REVTe
A Model of Curvature-Induced Phase Transitions in Inflationary Universe
Chiral phase transitions driven by space-time curvature effects are
investigated in de Sitter space in the supersymmetric Nambu-Jona-Lasinio model
with soft supersymmetry breaking. The model is considered to be suitable for
the analysis of possible phase transitions in inflationary universe. It is
found that a restoration of the broken chiral symmetry takes place in two
patterns for increasing curvature : the first order and second order phase
transition respectively depending on initial settings of the four-body
interaction parameter and the soft supersymmetry breaking parameter. The
critical curves expressing the phase boundaries in these parameters are
obtained. Cosmological implications of the result are discussed in connection
with bubble formations and the creation of cosmic strings during the
inflationary era.Comment: 12 pages, 3 figures, REVTe
Mathematical modeling of the geothermal reservoir with multi-borehole circulating system
A three-dimensional model (FRACSIM-3D) developed in Tohoku University for numerical simulation of heat and fluid flow within the fractured media is used in the analysis of geothermal reservoir performance. The model effectively simulates two main stages of the geothermal reservoir exploitation, namely, (i) hydraulic stimulation of the existing natural fractures within the Hot Dry Rock (HDR) reservoir and (ii) forced convection through the fractured media when the filtrating fluid extracts the heat from the hot rock and delivers it to the production well. Since the heat accumulated by the fluid within the system of injection boreholes can constitute a substantial fraction of the total thermal output of the geothermal power plant, the model of heat and mass transfer in the fractured media at the heat extraction stage should be coupled with the equations which describe the heat transport in the system of injection and production wells. Mathematical modeling of heat flow within the multi-borehole circulating system is proposed in this study. On the basis of this model the major parameters that affect the thermal productivity of the geothermal power plant are analyzed. The effective regimes of the fluid circulation and optimal geometry of the multi-borehole system are proposed
Mathematical modeling of the geothermal reservoir with multi-borehole circulating system
A three-dimensional model (FRACSIM-3D) developed in Tohoku University for numerical simulation of heat and fluid flow within the fractured media is used in the analysis of geothermal reservoir performance. The model effectively simulates two main stages of the geothermal reservoir exploitation, namely, (i) hydraulic stimulation of the existing natural fractures within the Hot Dry Rock (HDR) reservoir and (ii) forced convection through the fractured media when the filtrating fluid extracts the heat from the hot rock and delivers it to the production well. Since the heat accumulated by the fluid within the system of injection boreholes can constitute a substantial fraction of the total thermal output of the geothermal power plant, the model of heat and mass transfer in the fractured media at the heat extraction stage should be coupled with the equations which describe the heat transport in the system of injection and production wells. Mathematical modeling of heat flow within the multi-borehole circulating system is proposed in this study. On the basis of this model the major parameters that affect the thermal productivity of the geothermal power plant are analyzed. The effective regimes of the fluid circulation and optimal geometry of the multi-borehole system are proposed. Copyright © 2002 by ASME
Mass Hierarchies and the Seesaw Neutrino Mixing
We give a general analysis of neutrino mixing in the seesaw mechanism with
three flavors. Assuming that the Dirac and u-quark mass matrices are similar,
we establish simple relations between the neutrino parameters and individual
Majorana masses. They are shown to depend rather strongly on the physical
neutrino mixing angles. We calculate explicitly the implied Majorana mass
hierarchies for parameter sets corresponding to different solutions to the
solar neutrino problem.Comment: 11 pages, no figures, replaced with final version. Minor corrections
and one typo corrected. Added one referenc
New Development of the J -Based Fracture Testing Technique for Ceramic-Matrix Composites
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65733/1/j.1151-2916.1994.tb09756.x.pd
Androgen receptor and ultrastructural features of Nigella sativa oil and nicotine-treated male rat reproductive glands
Nicotine is claimed to increase free radicals, DNA damage and lipid peroxidation in male reproductive organs. Nigella sativa has been identified to ameliorate these adverse effects due to nicotine intake. This study was conducted to evaluate potential protective effects of N. sativa oil on the adverse effects of nicotine on androgen receptors (AR) and ultrastructural features of rat seminal vesicles and prostate glands. Twenty four Sprague Dawley male rats, 7-9 weeks of age and 200-250 g body weight (BW) were randomly divided into; Group 1 Saline (S), forced fed with 0.1 mL/100 g BW of 0.9% normal saline; Group 2 Nicotine (N), intramuscularly injected with 0.5 mg/100 g BW of nicotine; Group 3 N. sativa (NS), forced fed with 6.0 μL/100 g BW of N. sativa and Group 4 Nicotine-N. sativa (NNS), co-administered with 0.5 mg/100 g BW of nicotine and 6.0 μL/100 g BW of N. sativa. The seminal vesicles and prostate glands were extracted after 100 days of treatment. The seminal vesicle and prostate gland were processed for ultrastructural study and androgen receptor detection. The epithelial cells in prostate gland and seminal vesicle of the N group showed weaker brown staining intensity as compared to that of in the NS and NNS groups. This was consistent with the presence of some ultracellular changes observed in the prostate gland and seminal vesicle tissues of the N group. Findings from this study suggested that administration of N. sativa results in ameliorating effects on both the prostate gland and seminal vesicle structures and functions of the nicotine-treated rats
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