Cornell UniversityUniversidad de Cornell, USAhttps://repositorio.leon.uia.mx/xmlui/handle/20.500.12152/294622022-08-12T21:58:34Z2022-08-12T21:58:34ZProspects for precision measurements of atomic helium using direct
frequency comb spectroscopyhttps://repositorio.leon.uia.mx/xmlui/handle/20.500.12152/433482012-06-08T14:39:57Z2012-06-08T00:00:00ZProspects for precision measurements of atomic helium using direct
frequency comb spectroscopy
We analyze several possibilities for precisely measuring electronic
transitions in atomic helium by the direct use of phase-stabilized femtosecond
frequency combs. Because the comb is self-calibrating and can be shifted into
the ultraviolet spectral region via harmonic generation, it offers the prospect
of greatly improved accuracy for UV and far-UV transitions. To take advantage
of this accuracy an ultracold helium sample is needed. For measurements of the
triplet spectrum a magneto-optical trap (MOT) can be used to cool and trap
metastable 2^3S state atoms. We analyze schemes for measuring the two-photon
$2^3S \to 4^3S$ interval, and for resonant two-photon excitation to high
Rydberg states, $2^3S \to 3^3P \to n^3S,D$. We also analyze experiments on the
singlet-state spectrum. To accomplish this we propose schemes for producing and
trapping ultracold helium in the 1^1S or 2^1S state via intercombination
transitions. A particularly intriguing scenario is the possibility of measuring
the $1^1S \to 2^1S$ transition with extremely high accuracy by use of
two-photon excitation in a magic wavelength trap that operates identically for
both states. We predict a ``triple magic wavelength'' at 412 nm that could
facilitate numerous experiments on trapped helium atoms, because here the
polarizabilities of the 1^1S, 2^1S and 2^3S states are all similar, small, and
positive.; Comment: Shortened slightly and reformatted for Eur. Phys. J. D
2012-06-08T00:00:00ZLight Propagation on Quantum Curved Spacetime and Back reaction effectshttps://repositorio.leon.uia.mx/xmlui/handle/20.500.12152/433472012-06-08T14:39:53Z2012-06-08T00:00:00ZLight Propagation on Quantum Curved Spacetime and Back reaction effects
We study the electromagnetic field equations on an arbitrary quantum curved
background in the semiclassical approximation of Loop Quantum Gravity. The
effective interaction hamiltonian for the Maxwell and gravitational fields is
obtained and the corresponding field equations, which can be expressed as a
modified wave equation for the Maxwell potential, are derived. We use these
results to analyze electromagnetic wave propagation on a quantum
Robertson-Walker space time and show that Lorentz Invariance is not preserved.
The formalism developed can be applied to the case where back reaction effects
on the metric due to the electromagnetic field are taken into account, leading
to non covariant field equations.
2012-06-08T00:00:00ZGeneration of strongly chaotic beatshttps://repositorio.leon.uia.mx/xmlui/handle/20.500.12152/433462012-06-08T14:39:50Z2012-06-08T00:00:00ZGeneration of strongly chaotic beats
The letter proposes a procedure for generation of strongly chaotic beats that
have been hardly obtainable hitherto. The beats are generated in a nonlinear
optical system governing second-harmonic generation of light. The proposition
is based on the concept of an optical coupler but can be easily adopted to
other nonlinear systems and Chua's circuits.; Comment: 10 pages, 4 figures, accepted for publication in Int.J.Bif.Chaos
2012-06-08T00:00:00ZFive-parameter family of partial differential systems in two variableshttps://repositorio.leon.uia.mx/xmlui/handle/20.500.12152/433452012-06-08T14:39:47Z2012-06-08T00:00:00ZFive-parameter family of partial differential systems in two variables
We find a five-parameter family of partial differential systems in two
variables with two polynomial Hamiltonians. We give its symmetry and holomorphy
conditions. These symmetries, holomorphy conditions and invariant divisors are
new.; Comment: 9 pages, 2 figures
2012-06-08T00:00:00Z