546 research outputs found
Green's Functions and the Adiabatic Hyperspherical Method
We address the few-body problem using the adiabatic hyperspherical
representation. A general form for the hyperangular Green's function in
-dimensions is derived. The resulting Lippmann-Schwinger equation is solved
for the case of three-particles with s-wave zero-range interactions. Identical
particle symmetry is incorporated in a general and intuitive way. Complete
semi-analytic expressions for the nonadiabatic channel couplings are derived.
Finally, a model to describe the atom-loss due to three-body recombination for
a three-component fermi-gas of Li atoms is presented.Comment: 14 pages, 8 figures, 2 table
Flat Cellular (UMTS) Networks
Traditionally, cellular systems have been built in a hierarchical manner: many specialized cellular access network elements that collectively form a hierarchical cellular system. When 2G and later 3G systems were designed there was a good reason to make system hierarchical: from a cost-perspective it was better to concentrate traffic and to share the cost of processing equipment over a large set of users while keeping the base stations relatively cheap. However, we believe the economic reasons for designing cellular systems in a hierarchical manner have disappeared: in fact, hierarchical architectures hinder future efficient deployments. In this paper, we argue for completely flat cellular wireless systems, which need just one type of specialized network element to provide radio access network (RAN) functionality, supplemented by standard IP-based network elements to form a cellular network. While the reason for building a cellular system in a hierarchical fashion has disappeared, there are other good reasons to make the system architecture flat: (1) as wireless transmission techniques evolve into hybrid ARQ systems, there is less need for a hierarchical cellular system to support spatial diversity; (2) we foresee that future cellular networks are part of the Internet, while hierarchical systems typically use interfaces between network elements that are specific to cellular standards or proprietary. At best such systems use IP as a transport medium, not as a core component; (3) a flat cellular system can be self scaling while a hierarchical system has inherent scaling issues; (4) moving all access technologies to the edge of the network enables ease of converging access technologies into a common packet core; and (5) using an IP common core makes the cellular network part of the Internet
Ultralong-range polyatomic Rydberg molecules formed by a polar perturber
The internal electric field of a Rydberg atom electron can bind a polar
molecule to form a giant ultralong-range stable polyatomic molecule. Such
molecules not only share their properties with Rydberg atoms, they possess huge
permanent electric dipole moments and in addition allow for coherent control of
the polar molecule orientation. In this work, we include additional Rydberg
manifolds which couple to the nearly degenerate set of Rydberg states employed
in [S. T. Rittenhouse and H. R. Sadeghpour, Phys. Rev. Lett. 104, 243002
(2010)]. The coupling of a set of Rydberg states with the
nearly degenerate Rydberg manifolds in alkali metal atoms leads to pronounced
avoided crossings in the Born-Oppenheimer potentials. Ultimately, these avoided
crossings enable the formation of the giant polyatomic Rydberg molecules with
standard two-photon laser photoassociation techniques.Comment: 7 pages, 4 figure
Asymmetric Dark Matter and Baryogenesis from
We propose a theory in which the Standard Model gauge symmetry is extended by
a new group acting nontrivially on the lepton sector which is
spontaneously broken at the TeV scale. Under this the ordinary
leptons form doublets along with new lepton partner fields. This construction
naturally contains a dark matter candidate, the partner of the right-handed
neutrino, stabilized by a residual global symmetry. We show that
one can explain baryogenesis through an asymmetric dark matter scenario, in
which generation of related asymmetries in the dark matter and baryon sectors
is driven by the instantons during a first order phase transition
in the early universe.Comment: Version accepted for publication in Physical Review D. 11 pages, 4
figures. References added, minor change
Scattering of two particles in a one-dimensional lattice
This study concerns the two-body scattering of particles in a one-dimensional periodic potential. A convenient ansatz allows for the separation of center-of-mass and relative motion, leading to a discrete Schrodinger equation in the relative motion that resembles a tight-binding model. A lattice Green's function is used to develop the Lippmann-Schwinger equation, and ultimately derive a multiband scattering K matrix which is described in detail in the two-band approximation. Two distinct scattering lengths are defined according to the limits of zero relative quasimomentum at the top and bottom edges of the two-body collision band. Scattering resonances occur in the collision band when the energy is coincident with a bound state attached to another higher or lower band. Notably, repulsive on-site interactions in an energetically closed lower band lead to collision resonances in an excited band
Scattering of Two Particles in a One-Dimensional Lattice
This study concerns the two-body scattering of particles in a one-dimensional periodic potential. A convenient ansatz allows for the separation of center-of-mass and relative motion, leading to a discrete Schrödinger equation in the relative motion that resembles a tight-binding model. A lattice Green\u27s function is used to develop the Lippmann-Schwinger equation, and ultimately derive a multiband scattering Κ matrix which is described in detail in the two-band approximation. Two distinct scattering lengths are defined according to the limits of zero relative quasimomentum at the top and bottom edges of the two-body collision band. Scattering resonances occur in the collision band when the energy is coincident with a bound state attached to another higher or lower band. Notably, repulsive on-site interactions in an energetically closed lower band lead to collision resonances in an excited band
Observation of blue-shifted ultralong-range Cs Rydberg molecules
We observe ultralong-range blue-shifted Cs molecular states near
Rydberg states in an optical dipole trap, where .
The accidental near degeneracy of and Rydberg states for in
Cs, due to the small fractional quantum defect, leads to non-adiabatic
coupling among these states, producing potential wells above the
thresholds. Two important consequences of admixing high angular momentum states
with states are the formation of large permanent dipole moments, Debye, and accessibility of these states via two-photon association.
The observed states are in excellent agreement with theory. Both projections of
the total angular momentum on the internuclear axis are visible in the
experiment
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