21,750 research outputs found
Triple Products and Yang-Baxter Equation (II): Orthogonal and Symplectic Ternary Systems
We generalize the result of the preceeding paper and solve the Yang-Baxter
equation in terms of triple systems called orthogonal and symplectic ternary
systems. In this way, we found several other new solutions.Comment: 38 page
Cumulative Effects of Job Characteristics on Health
We present what we believe are the best estimates of how job characteristics of physical demands and environmental conditions affect individual’s health. Five-year cumulative measures of these job characteristics are used to reflect findings in the physiologic literature that cumulative exposure is most relevant for the impact of hazards and stresses on health. Using data from the Panel Study of Income Dynamics we find that individuals who work in jobs with the ‘worst’ conditions experience declines in their health, although this effect varies by demographic group. For example, for non-white men, a one standard deviation increase in cumulative physical demands decreases health by an amount that offsets an increase of two years of schooling or four years of aging. Job characteristics are found more detrimental to the health of females and older workers. These results are robust to inclusion of occupation fixed effects, health early in life and lagged health.Health, occupational characteristic
More on Gribov copies and propagators in Landau-gauge Yang-Mills theory
Fixing a gauge in the non-perturbative domain of Yang-Mills theory is a
non-trivial problem due to the presence of Gribov copies. In particular, there
are different gauges in the non-perturbative regime which all correspond to the
same definition of a gauge in the perturbative domain. Gauge-dependent
correlation functions may differ in these gauges. Two such gauges are the
minimal and absolute Landau gauge, both corresponding to the perturbative
Landau gauge. These, and their numerical implementation, are described and
presented in detail. Other choices will also be discussed.
This investigation is performed, using numerical lattice gauge theory
calculations, by comparing the propagators of gluons and ghosts for the minimal
Landau gauge and the absolute Landau gauge in SU(2) Yang-Mills theory. It is
found that the propagators are different in the far infrared and even at energy
scales of the order of half a GeV. In particular, also the finite-volume
effects are modified. This is observed in two and three dimensions. Some
remarks on the four-dimensional case are provided as well.Comment: 23 pages, 16 figures, 6 tables; various changes throughout most of
the paper; extended discussion on different possibilities to define the
Landau gauge and connection to existing scenarios; in v3: Minor changes,
error in eq. (3) & (4) corrected, version to appear in PR
Regularized Renormalization Group Reduction of Symplectic Map
By means of the perturbative renormalization group method, we study a
long-time behaviour of some symplectic discrete maps near elliptic and
hyperbolic fixed points. It is shown that a naive renormalization group (RG)
map breaks the symplectic symmetry and fails to describe a long-time behaviour.
In order to preserve the symplectic symmetry, we present a regularization
procedure, which gives a regularized symplectic RG map describing an
approximate long-time behaviour succesfully
Spin effects in single-electron transport through carbon nanotube quantum dots
We investigate the total spin in an individual single-wall carbon nanotube
quantum dot with various numbers of electrons in a shell by using the ratio of
the saturation currents of the first steps of Coulomb staircases for positive
and negative biases. The current ratio reflects the total-spin transition that
is increased or decreased when the dot is connected to strongly asymmetric
tunnel barriers. Our results indicate that total spin states with and without
magnetic fields can be traced by this method.Comment: 5pages, 5figures, accepted for publication in Phys. Rev.
Photon Mass Bound Destroyed by Vortices
The Particle Data Group gives an upper bound on the photon mass eV from a laboratory experiment and lists, but does not adopt, an
astronomical bound eV, both of which are based on the
plausible assumption of large galactic vector-potential. We argue that the
interpretations of these experiments should be changed, which alters
significantly the bounds on . If arises from a Higgs effect, both limits
are invalid because the Proca vector-potential of the galactic magnetic field
may be neutralized by vortices giving a large-scale magnetic field that is
effectively Maxwellian. In this regime, experiments sensitive to the Proca
potential do not yield a useful bound on . As a by-product, the non-zero
photon mass from Higgs effect predicts generation of a primordial magnetic
field in the early universe. If, on the other hand, the galactic magnetic field
is in the Proca regime, the very existence of the observed large-scale magnetic
field gives kpc, or eV.Comment: 9 pages, discussion of primordial magnetic field adde
Geometric Approach to Lyapunov Analysis in Hamiltonian Dynamics
As is widely recognized in Lyapunov analysis, linearized Hamilton's equations
of motion have two marginal directions for which the Lyapunov exponents vanish.
Those directions are the tangent one to a Hamiltonian flow and the gradient one
of the Hamiltonian function. To separate out these two directions and to apply
Lyapunov analysis effectively in directions for which Lyapunov exponents are
not trivial, a geometric method is proposed for natural Hamiltonian systems, in
particular. In this geometric method, Hamiltonian flows of a natural
Hamiltonian system are regarded as geodesic flows on the cotangent bundle of a
Riemannian manifold with a suitable metric. Stability/instability of the
geodesic flows is then analyzed by linearized equations of motion which are
related to the Jacobi equations on the Riemannian manifold. On some geometric
setting on the cotangent bundle, it is shown that along a geodesic flow in
question, there exist Lyapunov vectors such that two of them are in the two
marginal directions and the others orthogonal to the marginal directions. It is
also pointed out that Lyapunov vectors with such properties can not be obtained
in general by the usual method which uses linearized Hamilton's equations of
motion. Furthermore, it is observed from numerical calculation for a model
system that Lyapunov exponents calculated in both methods, geometric and usual,
coincide with each other, independently of the choice of the methods.Comment: 22 pages, 14 figures, REVTeX
Exotic criticality in the dimerized spin-1 chain with single-ion anisotropy
We consider the dimerized spin-1 chain with single-ion anisotropy .
In absence of an explicit dimerization there are three phases: a large-, an
antiferromagnetically ordered and a Haldane phase. This phase structure
persists up to a critical dimerization, above which the Haldane phase
disappears. We show that for weak dimerization the phases are separated by
Gaussian and Ising quantum phase transitions. One of the Ising transitions
terminates in a critical point in the universality class of the dilute Ising
model. We comment on the relevance of our results to experiments on
quasi-one-dimensional anisotropic spin-1 quantum magnets.Comment: Received the Select label. 20 pages, 7 figures, final versio
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