622 research outputs found
Influence of Carbon Concentration on the Superconductivity in MgCxNi3
The influence of carbon concentration on the superconductivity (SC) in
MgCNi has been investigated by measuring the low temperature specific
heat combined with first principles electronic structure calculation. It is
found that the specific heat coefficient of the
superconducting sample () in normal state is twice that of the
non-superconducting one (). The comparison of measured
and the calculated electronic density of states (DOS) shows that the
effective mass renormalization changes remarkably as the carbon concentration
changes. The large mass renormalization for the superconducting sample and the
low (7K) indicate that more than one kind of boson mediated
electron-electron interactions exist in MgCNi.Comment: 4 pages, 4 figure
Extended Birkhoff's Theorem in the f(T) Gravity
The f(T) theory, a generally modified teleparallel gravity, has been proposed
as an alternative gravity model to account for the dark energy phenomena.
Following our previous work [Xin-he Meng and Ying-bin Wang, EPJC(2011),
arXiv:1107.0629v1], we prove that the Birkhoff's theorem holds in a more
general context, specifically with the off diagonal tetrad case, in this
communication letter. Then, we discuss respectively the results of the external
vacuum and internal gravitational field in the f(T) gravity framework, as well
as the extended meaning of this theorem. We also investigate the validity of
the Birkhoff's theorem in the frame of f(T) gravity via conformal
transformation by regarding the Brans-Dicke-like scalar as effective matter,
and study the equivalence between both Einstein frame and Jordan frame.Comment: 7 pages, 1 figure, submitted to EPJ-C. arXiv admin note: substantial
text overlap with arXiv:1107.062
Birkhoff's Theorem in f(T) Gravity up to the Perturbative Order
f(T) gravity, a generally modified teleparallel gravity, has become very
popular in recent times as it is able to reproduce the unification of inflation
and late-time acceleration without the need of a dark energy component or an
inflation field. In this present work, we investigate specifically the range of
validity of Birkhoff's theorem with the general tetrad field via perturbative
approach. At zero order, Birkhoff's theorem is valid and the solution is the
well known Schwarzschild-(A)dS metric. Then considering the special case of the
diagonal tetrad field, we present a new spherically symmetric solution in the
frame of f(T) gravity up to the perturbative order. The results with the
diagonal tetrad field satisfy the physical equivalence between the Jordan and
the so-called Einstein frames, which are realized via conformal transformation,
at least up to the first perturbative order.Comment: 8 pages, no figure. Final version, accepted for publication in EPJ
Ultrafast photoinduced reflectivity transients in
The temperature dependence of ultrafast photoinduced reflectivity transients
is reported in NdSrMnO thin film. The photoinduced
reflectivity shows a complex response with very different temperature
dependences on different timescales. The response on the sub-ps timescale
appears to be only weakly sensitive to the 270K-metal-insulator phase
transition. Below K the sub-ps response displays a two component
behavior indicating inhomogeneity of the film resulting from the substrate
induced strain. On the other hand, the slower response on the 10-100 ps
timescale is sensitive only to the metal-insulator phase transition and is in
agreement with some previously published results. The difference in the
temperature dependences of the responses on nanosecond and s timescales
indicates that thermal equilibrium between the different degrees of fredom is
established relatively slowly - on a nanosecond timescale
Hydrological impact assessment on permeable road pavement with subsurface precast micro-detention pond
The purpose of this paper is to study stormwater management potential of new
permeable pavement with subsurface micro-detention storage (PPDS) at low-speed
residential suburban area. The main features incorporated permeable pavement
of a hollow micro cylinder precast structure with solid hexagon precast concrete
as top and bottom covers. The purpose of hollow micro detention design is for
rainwater holding and void between the sets is for self-drying through the side
and bottom seepage during rain. The hydrological parameters were obtained
from laboratory rainfall simulator experiment. The performance was evaluated
via simulation with Storm Water Management Model (SWMM). The outcomes
from the physical model matched well with SWMM. A case study was then developed
to assess the hydrological impact of PPDS with the existing condition
and other types of permeable pavements. Significant variance was observed,
where PPDS displayed its best hydrological performances for stormwater management
with the presence of subsurface detention storage
Electroweak Corrections to the Charged Higgs Boson Decay into Chargino and Neutralino
The electroweak corrections to the partial widths of the decays including one-loop
diagrams of the third generation quarks and squarks, are investigated within
the Supersymmetric Standard Model. The relative corrections can reach the
values about 10%, therefore they should be taken into account for the precise
experimental measurement at future colliders.Comment: 21 pages, 6 eps figures, 1 Latex fil
Measurements of the observed cross sections for exclusive light hadron production in e^+e^- annihilation at \sqrt{s}= 3.773 and 3.650 GeV
By analyzing the data sets of 17.3 pb taken at GeV
and 6.5 pb taken at GeV with the BESII detector at the
BEPC collider, we have measured the observed cross sections for 12 exclusive
light hadron final states produced in annihilation at the two energy
points. We have also set the upper limits on the observed cross sections and
the branching fractions for decay to these final states at 90%
C.L.Comment: 8 pages, 5 figur
Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-
We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi -->
D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7
J/Psi events collected with the BESII detector at the BEPC. No excess of signal
above background is observed, and 90% confidence level upper limits on the
branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi
--> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure
Measurements of psi(2S) decays to octet baryon-antibaryon pairs
With a sample of 14 million psi(2S) events collected by the BESII detector at
the Beijing Electron Positron Collider (BEPC), the decay channels psi(2S)->p
p-bar, Lambda Lambda-bar, Sigma0 Sigma0-bar, Xi Xi-bar are measured, and their
branching ratios are determined to be (3.36+-0.09+-0.24)*10E-4,
(3.39+-0.20+-0.32)*10E-4, (2.35+-0.36+-0.32)*10E-4, (3.03+-0.40+-0.32)*10E-4,
respectively. In the decay psi(2S)->p p-bar, the angular distribution parameter
alpha is determined to be 0.82+-0.17+-0.04.Comment: 8 pages, 8 figure
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