10,375 research outputs found
Two-pion-exchange parity-violating potential and
We calculate the parity-violating nucleon-nucleon potential in heavy-baryon
chiral perturbation theory up to the next-to-next-to-leading order. The
one-pion exchange comes in the leading order and the next-to-next-to-leading
order consists of two-pion-exchange and the two-nucleon contact terms. In order
to investigate the effect of the higher order contributions, we calculate the
parity-violating asymmetry in at the threshold. The
one-pion dominates the physical observable and the two-pion contribution is
about or less than 10% of the one-pion contribution.Comment: 3 pages, contribution to the workshop PAVI06 held in Milos island,
Greece, May 16-20, 200
Quantum Teichm\"uller space from quantum plane
We derive the quantum Teichm\"uller space, previously constructed by Kashaev
and by Fock and Chekhov, from tensor products of a single canonical
representation of the modular double of the quantum plane. We show that the
quantum dilogarithm function appears naturally in the decomposition of the
tensor square, the quantum mutation operator arises from the tensor cube, the
pentagon identity from the tensor fourth power of the canonical representation,
and an operator of order three from isomorphisms between canonical
representation and its left and right duals. We also show that the quantum
universal Teichm\"uller space is realized in the infinite tensor power of the
canonical representation naturally indexed by rational numbers including the
infinity. This suggests a relation to the same index set in the classification
of projective modules over the quantum torus, the unitary counterpart of the
quantum plane, and points to a new quantization of the universal Teichm\"uller
space.Comment: 41 pages, 9 figure
Parity Nonconservation in the Photodisintegration of the Deuteron at Low Energy
The parity-nonconserving asymmetry in the deuteron photodisintegration,
, is considered with the photon energy ranged up to 10
MeV above the threshold. The aim is to improve upon a schematic estimate
assuming the absence of tensor as well as spin-orbit forces in the
nucleon-nucleon interaction. The major contributions are due to the
vector-meson exchanges, and the strong suppression of the pion-exchange
contribution is confirmed. A simple argument, going beyond the observation of
an algebraic cancellation, is presented. Contributions of meson-exchange
currents are also considered, but found to be less significant.Comment: 12 pages, 6 figures, typeset by REVTeX (two-column format) and BIBTe
Sixteen-fermion and related terms in M-theory on T**2
Certain one-loop processes in eleven-dimensional supergravity compactified on
T**2 determine exact, non-perturbative, terms in the effective action of type
II string theories compactified on a circle. One example is the modular
invariant U(1)-violating interaction of sixteen complex spin-1/2 fermions of
ten-dimensional type IIB theory. This term, together with the (curvature)**4
term, and many other terms of the same dimension are all explicitly related by
supersymmetry.Comment: 14 Pages, Latex, no figures, Minor changes, version to appear in PL
Parity violation in scattering and vector-meson weak-coupling constants
We calculate the parity-nonconserving longitudinal asymmetry in the elastic
scattering at the energies where experimental data are available.
In addition to the standard one-meson exchange weak potential, the variation of
the strong-coupling constants and the non-standard effects such as form factors
and -exchange description of the -exchange potential are taken
into account. With the extra effects, we investigate the compatibility of the
experimental data and the presently-known range of the vector-meson
weak-coupling constants.Comment: Contribution to the proceedings of the 3rd Asia-Pacific conference on
few-body problems in physics, Suranaree Univ. of Technology, Nakhon
Ratchasima, Thailand, July 26 - 30, 200
Deuteron Anapole Moment with Heavy Mesons
Parity-nonconserving two-body currents due to vector meson exchange are
considered with the aim to determine the related contributions to the anapole
moment. A particular attention is given to the requirement of current
conservation which is essential for a reliable estimate of this quantity. An
application is made for the deuteron case.Comment: 23 pages, 5 EPS figures, uses REVTeX 4, v2: fixes layout problem
Testing Linearity in Cointegrating Relations with an Application to Purchasing Power Parity
This paper develops a linearity test that can be applied to cointegrating relations. We consider the widely used RESET specification test and show that when this test is applied to nonstationary time series its asymptotic distribution involves a mixture of noncentral chi^2 distributions, which leads to severe size distortions in conventional testing based on the central chi^2. Nonstationarity is shown to introduce two bias terms in the limit distribution, which are the source of the size distortion in testing. Appropriate corrections for this asymptotic bias leads to a modified version of the RESET test which has a central chi^2 limit distribution under linearity. The modified test has power not only against nonlinear cointegration but also against the absence of cointegration. Simulation results reveal that the modified test has good size infinite samples and reasonable power against many nonlinear models as well as models with no cointegration, confirming the analytic results. In an empirical illustration, the linear purchasing power parity (PPP) specification is tested using US, Japan, and Canada monthly data after Bretton Woods. While commonly used ADF and PP cointegration tests give mixed results on the presence of linear cointegration in the series, the modified test rejects the null of linear PPP cointegration.Nonlinear cointegration, Specification test, RESET test, Noncentral chi^2 distribution
Effect of ferromagnetic contacts on spin accumulation in an all-metallic lateral spin-valve system: Semiclassical spin drift-diffusion equations
We study the effect of the ferromagnetic (FM) contacts on the spin
accumulation in the lateral spin valve system for the collinear magnetization
configurations. When an additional FM electrode is introduced in the
all-metallic lateral spin-valve system, we find that the transresistance can be
fractionally suppressed or very weakly influenced depending on the position of
the additional FM electrode, and relative magnitudes of contact resistance and
the bulk resistance defined over the spin diffusion length. Nonlocal spin
signals such as nonlocal voltage drop and leakage spin currents are independent
of the magnetization orientation of the additional FM electrode. Even when the
additional contact is nonmagnetic, nonlocal spin signals can be changed by the
spin current leaking into the nonmagnetic electrode.Comment: 13 pages, 1 figure, revised versio
- …