70,451 research outputs found

### Superconductivity in ternary molybdenum sulfides

Three research papers are presented: (1) Superconductivity in Th-Zr Alloys; (2) Superconductivity in Pd-Si-H(D) alloys; and (3) Low Temperature Specific Heat of Amorphous Pd-Si Alloys

### Critical Relaxation and Critical Exponents

Dynamic relaxation of the XY model and fully frustrated XY model quenched
from an initial ordered state to the critical temperature or below is
investigated with Monte Carlo methods. Universal power law scaling behaviour is
observed. The dynamic critical exponent $z$ and the static exponent $\eta$ are
extracted from the time-dependent Binder cumulant and magnetization. The
results are competitive to those measured with traditional methods

### Superfluid response in electron-doped cuprate superconductors

We propose a weakly coupled two-band model with $d_{x^2-y^2}$ pairing
symmetry to account for the anomalous temperature dependence of superfluid
density $\rho_s$ in electron-doped cuprate superconductors. This model gives a
unified explanation to the presence of a upward curvature in $\rho_s$ near
$T_c$ and a weak temperature dependence of $\rho_s$ in low temperatures. Our
work resolves a discrepancy in the interpretation of different experimental
measurements and suggests that the pairing in electron-doped cuprates has
predominately $d_{x^2-y^2}$ symmetry in the whole doping range.Comment: 4 pages, 3 figures, title changed and references adde

### Consistent forcing scheme in the cascaded lattice Boltzmann method

In this paper, we give a more pellucid derivation for the cascaded lattice
Boltzmann method (CLBM) based on a general multiple-relaxation-time (MRT) frame
through defining a shift matrix. When the shift matrix is a unit matrix, the
CLBM degrades into an MRT LBM. Based on this, a consistent forcing scheme is
developed for the CLBM. The applicability of the non-slip rule, the
second-order convergence rate in space and the property of isotropy for the
consistent forcing scheme is demonstrated through the simulation of several
canonical problems. Several other existing force schemes previously used in the
CLBM are also examined. The study clarifies the relation between MRT LBM and
CLBM under a general framework

### A minimal approach to the scattering of physical massless bosons

Tree and loop level scattering amplitudes which involve physical massless
bosons are derived directly from physical constraints such as locality,
symmetry and unitarity, bypassing path integral constructions. Amplitudes can
be projected onto a minimal basis of kinematic factors through linear algebra,
by employing four dimensional spinor helicity methods or at its most general
using projection techniques. The linear algebra analysis is closely related to
amplitude relations, especially the Bern-Carrasco-Johansson relations for gluon
amplitudes and the Kawai-Lewellen-Tye relations between gluons and graviton
amplitudes. Projection techniques are known to reduce the computation of loop
amplitudes with spinning particles to scalar integrals. Unitarity, locality and
integration-by-parts identities can then be used to fix complete tree and loop
amplitudes efficiently. The loop amplitudes follow algorithmically from the
trees. A range of proof-of-concept examples is presented. These include the
planar four point two-loop amplitude in pure Yang-Mills theory as well as a
range of one loop amplitudes with internal and external scalars, gluons and
gravitons. Several interesting features of the results are highlighted, such as
the vanishing of certain basis coefficients for gluon and graviton amplitudes.
Effective field theories are naturally and efficiently included into the
framework. The presented methods appear most powerful in non-supersymmetric
theories in cases with relatively few legs, but with potentially many loops.
For instance, iterated unitarity cuts of four point amplitudes for
non-supersymmetric gauge and gravity theories can be computed by matrix
multiplication, generalising the so-called rung-rule of maximally
supersymmetric theories. The philosophy of the approach to kinematics also
leads to a technique to control color quantum numbers of scattering amplitudes
with matter.Comment: 65 pages, exposition improved, typos correcte

### Bound States and Critical Behavior of the Yukawa Potential

We investigate the bound states of the Yukawa potential $V(r)=-\lambda
\exp(-\alpha r)/ r$, using different algorithms: solving the Schr\"odinger
equation numerically and our Monte Carlo Hamiltonian approach. There is a
critical $\alpha=\alpha_C$, above which no bound state exists. We study the
relation between $\alpha_C$ and $\lambda$ for various angular momentum quantum
number $l$, and find in atomic units, $\alpha_{C}(l)= \lambda [A_{1} \exp(-l/
B_{1})+ A_{2} \exp(-l/ B_{2})]$, with $A_1=1.020(18)$, $B_1=0.443(14)$,
$A_2=0.170(17)$, and $B_2=2.490(180)$.Comment: 15 pages, 12 figures, 5 tables. Version to appear in Sciences in
China

### Why Use a Hamilton Approach in QCD?

We discuss $QCD$ in the Hamiltonian frame work. We treat finite density $QCD$
in the strong coupling regime. We present a parton-model inspired
regularisation scheme to treat the spectrum ($\theta$-angles) and distribution
functions in $QED_{1+1}$. We suggest a Monte Carlo method to construct
low-dimensionasl effective Hamiltonians. Finally, we discuss improvement in
Hamiltonian $QCD$.Comment: Proceedings of Hadrons and Strings, invited talk given by H.
Kr\"{o}ger; Text (LaTeX file), 3 Figures (ps file

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