1,336 research outputs found
Apparent negative motion of vortex matter due to inhomogeneous pinning
We investigate the transport of vortices in superconductors with inhomgeneous pinning under a driving force. The inhomogeneity of pinning is simplified as strong-weak pinning regions. It is demonstrated that the interactions between the vortices captured by strong pinning potentials and the vortices in the weak pinning region cause absolute negative motion (ANM) of vortices: The vortices which are climbing toward the high barriers induced by the strong pinning with the help of driving force move toward the opposite direction of the force and back to their equilibrium positions in the weak pinning region as the force decreases or is withdrawn. Our simulations reveal that the hysteresis of ANM is determined by the competition between the speed of the negative motion which depends on the piining inhomogeneity in superconductors and the speed of the driving force. Under the conditions of either larger force scanning rate or higher pinning inhomogeneity, a marked ANM and a larger hysteretic speed-force loop could be observed. This indicates that the time window to observe the ANM should be chosen properly. Moreover, the V-1 characteristics of Ag-sheathed Bi=2223 tapes are measured, and experimental observations are qualitatively in agreement with the simulation
Semi-classical theory of magnetic quantum oscillations in a two-dimensional multiband canonical Fermi liquid
The semi-classical Lifshitz-Kosevich (LK) description of quantum oscillations
is extended to a multiband two-dimensional Fermi liquid with a constant number
of electrons. The amplitudes of novel oscillations with combination
frequencies, recently predicted and observed experimentally, are analytically
derived and compared with the single-band amplitudes. The combination
amplitudes decay with temperature exponentially faster than the standard
harmonics, and this provides a valuable tool for their experimental
identification.Comment: 3 pages, REVTeX 3.0, one eps-figure included in the tex
Measuring the Spin of the Higgs Boson
By studying the threshold dependence of the excitation curve and the angular
distribution in Higgs-strahlung at e+e- colliders, e+e- -> HZ, the spin of the
Higgs boson in the Standard Model and related extensions can be determined
unambiguously in a model-independent way.Comment: 10 pages, 1 Postscript figure, sign typo correcte
Top-quark spin correlation at Linear Colliders with anomalous couplings
We investigate the feasibility of probing anomalous top-quark couplings of
, , and in terms of an effective
Lagrangian with dimension-six operators at future linear colliders
with a c. m. energy GeV. We first examine the
constraints on these anomalous couplings from the data at LEP
I and from unitarity considerations. We then consider in detail the effects of
anomalous couplings on spin correlations in the top-pair production
and decay with three spin bases: the helicity, beamline and off-diagonal bases.
Our results show that the polarized beams are more suitable for exploring the
effects of different new operators. For polarized beams, the helicity basis
yields the best sensitivity.Comment: 23 pages, 10 figures, references adde
Continuous Wavelets on Compact Manifolds
Let be a smooth compact oriented Riemannian manifold, and let
be the Laplace-Beltrami operator on . Say 0 \neq f
\in \mathcal{S}(\RR^+), and that . For , let
denote the kernel of . We show that is
well-localized near the diagonal, in the sense that it satisfies estimates akin
to those satisfied by the kernel of the convolution operator on
\RR^n. We define continuous -wavelets on , in such a
manner that satisfies this definition, because of its localization
near the diagonal. Continuous -wavelets on are analogous to
continuous wavelets on \RR^n in \mathcal{S}(\RR^n). In particular, we are
able to characterize the Hlder continuous functions on by
the size of their continuous wavelet transforms, for
Hlder exponents strictly between 0 and 1. If is the torus
\TT^2 or the sphere , and (the ``Mexican hat''
situation), we obtain two explicit approximate formulas for , one to be
used when is large, and one to be used when is small
Loop-Induced CP Violation in the Gaugino and Higgsino Sectors of Supersymmetric Theories
We show that the gaugino and higgsino sectors of supersymmetric theories can
naturally acquire observable CP violation through radiative effects which
originate from large CP-violating trilinear couplings of the Higgs bosons to
the third-generation scalar quarks. These CP-violating loop effects are not
attainable by evolving the supersymmetric renormalization-group equations from
a higher unification scale down to the electroweak one. We briefly discuss the
phenomenological consequences of such a scenario, and as an example, calculate
the two-loop contribution to the neutron electric dipole moment generated by
the one-loop chromo-electric dipole moment of the gluino.Comment: 9 pages, as to appear in Physical Review
Direct Signals for Large Extra Dimensions in the Production of Fermion Pairs at Linear Colliders
We analyze the potentiality of the new generation of linear
colliders to search for large extra dimensions via the production of fermion
pairs in association with Kaluza-Klein gravitons (G), i.e. . This process leads to a final state exhibiting a significant amount
of missing energy in addition to acoplanar lepton or jet pairs. We study in
detail this reaction using full tree level contibutions due to the graviton
emission and the standard model backgrounds. After choosing the cuts to enhance
the signal, we show that a linear collider with a center-of-mass energy of 500
GeV will be able to probe quantum gravity scales from 0.96(0.86) up to 4.1(3.3)
TeV at 2(5) level, depending on the number of extra dimensions.Comment: 19 pages, 5 figures. Using RevTex, axodraw.sty. Discussion was
extended. No changes in the results. Accepted for publication by Phys. Rev.
Mechanical Properties of Dissimilar A356/SAPH440 Lap Joints by the Friction Stir Spot Welding and Self-Piercing Riveting
Aluminum alloy A356-T6 and automotive steel sheet SAPH440 were joined using friction stir spot welding and self-piercing riveting. The maximum tensile shear strength values in weld joints were approximately 3.5 kN at a rotation speed of 500 rpm and plunge depth of 1.0 mm. It was confirmed that the intermetallic compound layer of weld joints below 9.23 m did not exceed the permissible thickness 10 m of Al–Fe joints. The self-piercing riveting joints exhibited maximum tensile- shear strength of 7.9 kN, which was higher than that of the weld joints. However, during the riveting process, cracking appeared in the joint on the aluminum side, which was caused by lack of ductility of cast aluminum. In addition, it was observed that the cracks on the aluminum side were getting larger, as the radius of the lower mold increased.Алюминиевый сплав А356-Т6 и автомобильную листовую сталь SAPH440 соединяли с помощью точечной ротационной сварки трением и самопробивной клепки. Максимальный предел прочности на сдвиг при растяжении для сварных соединений составлял примерно 3,5 кН при скорости вращения 500 об/мин и глубине проникновения 1,0 мм. Доказано, что слой интерметаллидов сварных соединений толщиной менее 9,23 мкм не превышал допустимый уровень в 10 мкм для соединений Al–Fe. Клепаные соединения имели предел прочности 7,9 кН в отличие от сварных соединений. Однако при клепке на алюминии появлялись трещины ввиду низкой пластичности литого материала, при этом трещины подрастали по мере увеличения радиуса нижней формы
Pair Production of the Lightest Chargino via Gluon-Gluon Collisions
The production of the lightest chargino pair from gluon-gluon fusion is
studied in the minimal supersymmetric model(MSSM) at proton-proton colliders.
We find that with the chosen parameters, the production rate of the subprocess
can be over 2.7 femto barn when the chargino is higgsino-like, and the
corresponding total cross section in proton-proton collider can reach 56 femto
barn at the LHC in the CP-conserving MSSM. It shows that this loop mediated
subprocess can be competitive with the standard Drell-Yan subprocess in
proton-proton colliders, especially at the LHC. Furthermore, our calculation
shows it would be possible to extract information about some CP-violating phase
parameters, if we collected enough chargino pair events.Comment: 39 pages, LaTex, 8 figure
Spin configuration of top quark pair production with large extra dimensions at photon-photon colliders
Top quark pair production at photon-photon colliders is studied in low scale
quantum gravity scenario. From the dependence of the cross sections on the spin
configuration of the top quark and anti-quark, we introduce a new observable,
top spin asymmetry. It is shown that there exists a special top spin basis
where with the polarized parent electron beams the top spin asymmetry vanishes
in the standard model but retains substantial values with the large extra
dimension effects. We also present lower bounds of the quantum gravity scale
from total cross sections with various combinations of the laser,
electron beam, and top quark pair polarizations. The measurements of the top
spin state with unpolarized initial beams are
shown to be most effective, enhancing by about 5% the bounds with respect
to totally unpolarized case.Comment: 18 pages, 4 figures, ReVTe
- …