Search results for "COUPLING"
showing 10 items of 1862 documents
The spiked harmonic oscillatorV(r)=r 2+λr −4 as a challenge to perturbation theory
1991
The standard weak- and strong-coupling perturbation series are interpreted as extreme special cases of expansions obtainable within the framework of Rayleigh-Schroedinger perturbation theory with non-diagonal propagators and unspecified zero-order energies. The formalism of the latter type is then tested by our strongly singular example. It proves suitable for applications in the domain of virtually arbitrary couplings. A few related technicalities and especially the quadruple problem of convergence are also discussed.
Toward multifunctional molecular cells for quantum cellular automata: exploitation of interconnected charge and spin degrees of freedom
2021
We discuss the possibility of using mixed-valence (MV) dimers comprising paramagnetic metal ions as molecular cells for quantum cellular automata (QCA). Thus, we propose to combine the underlying idea behind the functionality of QCA of using the charge distributions to encode binary information with the additional functional options provided by the spin degrees of freedom. The multifunctional ('smart') cell is supposed to consist of multielectron MV d(n)-d(n+1)-type (1 ≤ n ≤ 8) dimers of transition metal ions as building blocks for composing bi-dimeric square planar cells for QCA. The theoretical model of such a cell involves the double exchange (DE), Heisenberg-Dirac-Van Vleck (HDVV) excha…
Flavor of cosmic neutrinos preserved by ultralight dark matter
2019
Within the standard propagation scenario, the flavor ratios of high-energy cosmic neutrinos at neutrino telescopes are expected to be around the democratic benchmark resulting from hadronic sources, $\left( 1 : 1 : 1 \right)_\oplus$. We show how the coupling of neutrinos to an ultralight dark matter complex scalar field would induce an effective neutrino mass that could lead to adiabatic neutrino propagation. This would result in the preservation at the detector of the production flavor composition of neutrinos at sources. This effect could lead to flavor ratios at detectors well outside the range predicted by the standard scenario of averaged oscillations. We also present an electroweak-in…
Kinetically Modified Non-Minimal Chaotic Inflation
2015
We consider Supersymmetric (SUSY) and non-SUSY models of chaotic inflation based on the phi^n potential with 2<=n<=6. We show that the coexistence of a nonminimal coupling to gravity, fR=1+cR phi^(n/2), with a kinetic mixing of the form fK=cK fR^m can accommodate values of the spectral index, ns, and the tensor-to-scalar ratio, r, favored by the Bicep2/Keck Array and Planck results for 0<=m<=4 and 2.5x10^(-4)<=rRK=cR/cK^{n/4}<=1, where the upper limit is not imposed for n=2. Inflation can be attained for subplanckian inflaton values with the corresponding effective theories retaining the perturbative unitarity up to the Planck scale.
Ghost spectral function from the spectral Dyson-Schwinger equation
2021
We compute the ghost spectral function in Yang-Mills theory by solving the corresponding Dyson-Schwinger equation for a given input gluon spectral function. The results encompass both scaling and decoupling solutions for the gluon propagator input. The resulting ghost spectral function displays a particle peak at vanishing momentum and a negative scattering spectrum, whose infrared and ultraviolet tails are obtained analytically. The ghost dressing function is computed in the entire complex plane, and its salient features are identified and discussed.
Running gravitational couplings, decoupling, and curved spacetime renormalization
2020
We propose to slightly generalize the DeWitt-Schwinger adiabatic renormalization subtractions in curved space to include an arbitrary renormalization mass scale $\mu$. The new predicted running for the gravitational couplings are fully consistent with decoupling of heavy massive fields. This is a somewhat improvement with respect to the more standard treatment of minimal (DeWitt-Schwinger) subtractions via dimensional regularization. We also show how the vacuum metamorphosis model emerges from the running couplings.
The momentum and the angular momentum of the Universe revisited. Some preliminary results
2007
We consider the question of properly defining energy and momenta for non asymptotic Minkowskian spaces in general relativity. Only those of these spaces which have zero energy, zero linear 3-momentum, and zero intrinsic angular momentum would be candidates to creatable universes, that is, to universes which could have arisen from a vacuum quantum fluctuation. Given a universe, we completely characterize the family of coordinate systems in which it would make sense saying that this universe can be a creatable universe.
A new technique in the theory of angular distributions in atomic processes: the angular distribution of photoelectrons in single and double photoioni…
1996
Special reduction formulae for bipolar harmonics with higher ranks of internal spherical functions are derived, which will be useful in problems involving multiple expansions in spherical functions. Together with irreducible tensor operator techniques these results provide a new and effective approach, which enables one to extract the geometrical and dynamical factors from the cross sections of atomic processes with polarized particles with an accurate account of all the polarization effects. The angular distribution of polarized electrons and the circular dichroism in photoionization of polarized atoms with an arbitrary angular momentum are presented in an invariant vector form. A specific…
Generation of Schrödinger Cats in Trapped Ions
2004
A quantum system in interaction with a repeatedly measured one is subjected to a non-unitary time evolution provoking the decay of some states in favor of the remaining ones. Under appropriate hypotheses the system may be addressed exactly toward a quantum state or pushed into a pre-selected finite-dimensional subspace. On the basis of such a general strategy, we propose to exploit suitable vibronic couplings in order to ‘extract’ trapped ion center of mass states of motion characterized by well defined absolute value of an angular momentum projection. In particular, since it implies the simultaneous presence of opposite angular momentum projections, we show the realizability of Schrödinger…
Determination of the ground-state hyperfine structure in neutral229Th
2012
The ground-state hyperfine structure of neutral 229Th has been measured for the first time using high-resolution resonance ionization spectroscopy. The measurements were performed as a preparatory work aimed at the identification of the predicted low-lying 7.6 eV isomer in 229Th through an investigation of its hyperfine structure. The hyperfine coupling constants have been extracted for the atomic ground state as well as for three excited states at 26 096, 26 113 and 38 278 cm−1. Due to rather small splittings not all hyperfine components were completely resolved and therefore an extensive χ2-error analysis was performed to achieve reliable results. The ground-state transition to the excite…