449 research outputs found
A Faddeev-Niemi Solution that Does Not Satisfy Gauss' Law
Faddeev and Niemi have proposed a reformulation of SU(2) Yang-Mills theory in
terms of a U(1) gauge theory with 8 off-shell degrees of freedom. We present a
solution to Faddeev and Niemi's formulation which does not solve the SU(2)
Yang-Mills Gauss constraints. This demonstrates that the proposed reformulation
is inequivalent to Yang-Mills, but instead describes Yang-Mills coupled to a
particular choice of external charge.Comment: 10 pages, no figure
Dynamical mass generation in quantum field theory : some methods with application to the Gross-Neveu model and Yang-Mills theory
We introduce some techniques to investigate dynamical mass generation. The
Gross-Neveu model (GN) is used as a toy model, because the GN mass gap is
exactly known, making it possible to check reliability of the various methods.
Very accurate results are obtained. Also application to SU(N) Yang-Mills (YM)
is discussed.Comment: 8 LaTeX2e pages, uses Kluwer class file crckbked.cls. Kluwer package
included. To appear in: Proceedings of the NATO Advanced Research Workshop on
"Confinement, Topology, and other Non-Perturbative Aspects of QCD", Stara
Lesna, Slovakia, 21-27 jan 200
Formability of micro sheet hydroforming of ultra-fine grained stainless steel
© 2014 The Authors. Published by Elsevier Ltd. The formability of ultra-fine grained stainless steel is investigated in micro hydromechanical deep drawing. The materials used are ultra-fine grained stainless steel and SUS304-H with thickness of 20 and 50 m. The micro cups are successfully fabricated for the ultra-fine grained stainless steel but it cannot be fabricated for SUS304-H with thickness of 20 m. The fracture type of ultra-fine grained stainless steel foil is the shortage of tensile strength at plain strain state and does not change with a decrease of the thickness. In contrast, the fracture type of SUS304-H foil changes to the bending deformation with decreasing the thickness due to its low ductility. The ultra-fine grained metal foil is required to obtain the high formability and fabricate the sharp micro cups
Zero Temperature Chiral Phase Transition in (2+1)-Dimensional QED with a Chern-Simons Term
We investigate the zero temperature chiral phase transition in
(2+1)-dimensional QED in the presence of a Chern-Simons term, changing the
number of fermion flavors. In the symmetric phase, there are no light degrees
of freedom even at the critical point. Unlike the case without a Chern-Simons
term, the phase transition is first-order.Comment: 7 pages, RevTeX, no figure
Combined Influences of Gradual Changes in Room Temperature and Light around Dusk and Dawn on Circadian Rhythms of Core Temperature, Urinary 6-Hydroxymelatonin Sulfate and Waking Sensation Just after Rising
The present experiment aimed at knowing how a gradual changes of room temperature (Ta) and light in the evening
and early morning could influence circadian rhythms of core temperature (Tcore), skin temperatures, urinary 6-hydroxymelatonin
sulfate and waking sensation just after rising in humans. Two kinds of room environment were provided
for each participant: 1) Constant room temperature (Ta) of 27 °C over the 24 h and LD-rectangular light change with
abrupt decreasing from 3,000 lx to100 lx at 1800,abrupt increasing from 0 lx to 3,000 lx at 0700. 2) Cyclic changes of Ta
and with gradual decrease from 3,000 lx to 100 lx onset at 1700 (twilight period about 2 h), with gradual increasing from
0 lx to 3,000 lx onset at 0500 (about 2 h). Main results are summarized as follows: 1) Circadian rhythms of nadir in the
core temperature (Tcore) significantly advanced earlier under the influence of gradual changes of Ta and light than no
gradual changes of Ta and light. 2) Nocturnal fall of Tcore and morning rise of Tcore were greater and quicker, respectively,
under the influence of gradual changes of Ta and light than no gradual changes of Ta and light. 3) Urinary 6-hydroxymelatonin
sulfate during nocturnal sleep was significantly greater under the influence of gradual changes of Ta and
light. 4) Waking sensation just after rising was significantly better under the influence of gradual changes of Ta and
light. We discussed these findings in terms of circadian and thermoregulatory physiology
Nonabelian Faddeev-Niemi Decomposition of the SU(3) Yang-Mills Theory
Faddeev and Niemi (FN) have introduced an abelian gauge theory which
simulates dynamical abelianization in Yang-Mills theory (YM). It contains both
YM instantons and Wu-Yang monopoles and appears to be able to describe the
confining phase. Motivated by the meson degeneracy problem in dynamical
abelianization models, in this note we present a generalization of the FN
theory. We first generalize the Cho connection to dynamical symmetry breaking
pattern SU(N+1) -> U(N), and subsequently try to complete the Faddeev-Niemi
decomposition by keeping the missing degrees of freedom. While it is not
possible to write an on-shell complete FN decomposition, in the case of SU(3)
theory of physical interest we find an off-shell complete decomposition for
SU(3) -> U(2) which amounts to partial gauge fixing, generalizing naturally the
result found by Faddeev and Niemi for the abelian scenario SU(N+1) -> U(1)^N.
We discuss general topological aspects of these breakings, demonstrating for
example that the FN knot solitons never exist when the unbroken gauge symmetry
is nonabelian, and recovering the usual no-go theorems for colored dyons.Comment: Latex 30 page
Na+ current expression in human atrial myofibroblasts: identity and functional roles
In the mammalian heart fibroblasts have important functional roles in both healthy conditions and diseased states. During pathophysiological challenges, a closely related myofibroblast cell population emerges, and can have distinct and significant roles.Recently, it has been reported that human atrial myofibroblasts can express a Na+ current, INa. Some of the biophysical properties and molecular features suggest that this INa is due to expression of Nav 1.5, the same Na+ channel α subunit that generates the predominant INa in myocytes from adult mammalian heart. In principle, expression of Nav 1.5 could give rise to regenerative action potentials in the fibroblasts/myofibroblasts. This would suggest an active as opposed to passive role for fibroblasts/myofibroblasts in both the ‘trigger’ and the ‘substrate’ components of cardiac rhythm disturbances.Our goals in this preliminary study were: (i) to confirm and extend the electrophysiological characterization of INa in a human atrial fibroblast/myofibroblast cell population maintained in conventional 2-D tissue culture; (ii) to identify key molecular properties of the α and β subunits of these Na+ channel(s); (iii) to define the biophysical and pharmacological properties of this INa ; (iv) to integrate the available multi-disciplinary data, and attempt to illustrate its functional consequences, using a mathematical model in which the human atrial myocyte is coupled via connexins to fixed numbers of fibroblasts/myofibroblasts in a syncytial arrangement.Our experimental findings confirm that a significant fraction (~40-50%) of these human atrial myofibroblasts can express INa. However, our results suggest that INa may be generated by Nav 1.9, Nav 1.2, and Nav 1.5. Our findings, when complemented with mathematical modeling, provide a background for re-evaluating pharmacological management of supraventricular rhythm disorders, e.g. persistent atrial fibrillation
Discrete Anomaly and Dynamical Mass in 2+1 dimensional Model
We note that in (2+1)-dimensional gauge theories with even number of massless
fermions, there is anomalous symmetry if theory is regularized in a
parity-invariant way. We then consider a parity invariant
model, which induces a mutual Chern-Simons term in the effective action due to
anomaly. The effect of the discrete anomaly is studied in the induced
spin and in the dynamical fermion mass.Comment: 14 pages, latex, two figures (available upon request
Sondheimer Oscillation as a Fingerprint of Surface Dirac Fermions
Topological states of matter challenge the paradigm of symmetry breaking,
characterized by gapless boundary modes and protected by the topological
property of the ground state. Recently, angle-resolved photoemission
spectroscopy (ARPES) has revealed that semiconductors of BiSe and
BiTe belong to such a class of materials. Here, we present
undisputable evidence for the existence of gapless surface Dirac fermions from
transport in BiTe. We observe Sondheimer oscillation in
magnetoresistance (MR). This oscillation originates from the quantization of
motion due to the confinement of electrons within the surface layer. Based on
Sondheimer's transport theory, we determine the thickness of the surface state
from the oscillation data. In addition, we uncover the topological nature of
the surface state, fitting consistently both the non-oscillatory part of MR and
the Hall resistance.
The side-jump contribution turns out to dominate around 1 T in Hall
resistance while the Berry-curvature effect dominates in 3 T 4 T
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