81,738 research outputs found
Calculation of accurate permanent dipole moments of the lowest states of heteronuclear alkali dimers using extended basis sets
The obtention of ultracold samples of dipolar molecules is a current
challenge which requires an accurate knowledge of their electronic properties
to guide the ongoing experiments. In this paper, we systematically investigate
the ground state and the lowest triplet state of mixed alkali dimers (involving
Li, Na, K, Rb, Cs) using a standard quantum chemistry approach based on
pseudopotentials for atomic core representation, gaussian basis sets, and
effective terms for core polarization effects. We emphasize on the convergence
of the results for permanent dipole moments regarding the size of the gaussian
basis set, and we discuss their predicted accuracy by comparing to other
theoretical calculations or available experimental values. We also revisit the
difficulty to compare computed potential curves among published papers, due to
the differences in the modelization of core-core interaction.Comment: accepted to J. Chem. Phy
Loop Equations and the Topological Phase of Multi-Cut Matrix Models
We study the double scaling limit of mKdV type, realized in the two-cut
Hermitian matrix model. Building on the work of Periwal and Shevitz and of
Nappi, we find an exact solution including all odd scaling operators, in terms
of a hierarchy of flows of matrices. We derive from it loop
equations which can be expressed as Virasoro constraints on the partition
function. We discover a ``pure topological" phase of the theory in which all
correlation functions are determined by recursion relations. We also examine
macroscopic loop amplitudes, which suggest a relation to 2D gravity coupled to
dense polymers.Comment: 24p
Dome craters on Ganymede
Voyager observations reveal impact craters on Ganymede that are characterized by the presence of broad, high albedo, topographic domes situated within a central pit. Fifty-seven craters with central domes were identified in images covering approx. 50% of the surface. Owing to limitations in resolution, and viewing and illumination angles, the features identified are most likely a subset of dome craters. The sample appears to be sufficiently large to infer statistically meaningful trends. Dome craters appear to fall into two distinct populations on plots of the ratio of dome diameter to crater rim diameter, large-dome craters and small-dome craters. The two classes are morphologically distinct from one another. In general, large dome craters show little relief and their constituent landforms appear subdued with respect to fresh craters. The physical attributes of small-dome craters are more sharply defined, a characteristic they share with young impact craters of comparable size observed elsewhere in the solar system. Both types of dome craters exhibit central pits in which the dome is located. As it is difficult to produce domes by impact and/or erosional processes, an endogenic origin for the domes is reasonably inferred. Several hypotheses for their origin are proposed. These hypotheses are briefly reviewed
Berry phase and Anomalous Hall Effect in a Three-orbital Tight-binding Hamiltonian
We consider the Anomalous Hall (AH) state induced by interactions in a
three-orbital per unit-cell model. To be specific we consider a model
appropriate for the Copper-Oxide lattice to highlight the necessary conditions
for time-reversal breaking states which are AH states and which are not. We
compare the singularities of the wave-functions of the three-orbital model,
which are related to the nonzero Berry curvature, and their variation with a
change of gauge to those in the two-orbital model introduced in a seminal paper
by Haldane. Explicit derivation using wave-functions rather than the more
powerful abstract methods may provide additional physical understanding of the
phenomena
Transport properties of the one-dimensional Hubbard model at finite temperature
We study finite-temperature transport properties of the one-dimensional
Hubbard model using the density matrix renormalization group. Our aim is
two-fold: First, we compute both the charge and the spin current correlation
function of the integrable model at half filling. The former decays rapidly,
implying that the corresponding Drude weight is either zero or very small.
Second, we calculate the optical charge conductivity sigma(omega) in presence
of small integrability-breaking next-nearest neighbor interactions (the
extended Hubbard model). The DC conductivity is finite and diverges as the
temperature is decreased below the gap. Our results thus suggest that the
half-filled, gapped Hubbard model is a normal charge conductor at finite
temperatures. As a testbed for our numerics, we compute sigma(omega) for the
integrable XXZ spin chain in its gapped phase
Electroweak Baryogenesis with dimension-6 Higgs interactions
We present the computation of the baryon asymmetry in the SM amplified by
dimension-6 Higgs interactions using the WKB approximation. Analyzing the
one-loop potential it turns out that the phase transition is strongly first
order in a wide range of the parameters. It is ensured not to wash out the net
baryon number gained previously even for Higgs masses up to at least 170 GeV.
In addition dimension-6 operators induce new sources of CP violation. Novel
source terms which enhance the generated baryon asymmetry emerge in the
transport equations. This model predicts a baryon to entropy ratio close to the
observed value for a large part of the parameter space.Comment: 10 pages, 4 figures, Talk given at the 8th International Moscow
School of Physic
Structure of the Alkali-metal-atom-Strontium molecular ions: towards photoassociation and formation of cold molecular ions
The potential energy curves, permanent and transition dipole moments, and the
static dipolar polarizability, of molecular ions composed of one alkali-metal
atom and a Strontium ion are determined with a quantum chemistry approach. The
molecular ions are treated as effective two-electron systems and are treated
using effective core potentials including core polarization, large gaussian
basis sets, and full configuration interaction. In the perspective of upcoming
experiments aiming at merging cold atom and cold ion traps, possible paths for
radiative charge exchange, photoassociation of a cold Lithium or Rubidium atom
and a Strontium ion are discussed, as well as the formation of stable molecular
ions
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