262 research outputs found
Super coset space geometry
Super coset spaces play an important role in the formulation of
supersymmetric theories. The aim of this paper is to review and discuss the
geometry of super coset spaces with particular focus on the way the geometrical
structures of the super coset space G/H are inherited from the super Lie group
G. The isometries of the super coset space are discussed and a definition of
Killing supervectors - the supervectors associated with infinitesimal
isometries - is given that can be easily extended to spaces other than coset
spaces.Comment: 49 pages, 1 figure, AFK previously published under the name A. F.
Schunc
Seesaw parametrization for n right-handed neutrinos
Introducing n right-handed neutrinos to the Standard Model yields, in
general, massive active neutrinos. We give explicit parametrizations for the
involved mixing and coupling matrices in terms of physical parameters for both
the top-down and the bottom-up approach for arbitrary n. Bounds on the complex
mixing angles in the bottom-up approach from perturbativity of the Yukawa
couplings to charged lepton flavor violation are discussed. As a novel
illustration of possible effects from n != 3, we extend the neutrino anarchy
framework to arbitrary n; we show that while the anarchic mixing angles are
insensitive to the number of singlets, the observed ratios of neutrino masses
prefer small n for the simplest linear measure.Comment: 12 pages, 4 figures. Added references and details about the sampling
algorith
Graded Majorana spinors
In many mathematical and physical contexts spinors are treated as Grassmann
odd valued fields. We show that it is possible to extend the classification of
reality conditions on such spinors by a new type of Majorana condition. In
order to define this graded Majorana condition we make use of
pseudo-conjugation, a rather unfamiliar extension of complex conjugation to
supernumbers. Like the symplectic Majorana condition, the graded Majorana
condition may be imposed, for example, in spacetimes in which the standard
Majorana condition is inconsistent. However, in contrast to the symplectic
condition, which requires duplicating the number of spinor fields, the graded
condition can be imposed on a single Dirac spinor. We illustrate how graded
Majorana spinors can be applied to supersymmetry by constructing a globally
supersymmetric field theory in three-dimensional Euclidean space, an example of
a spacetime where standard Majorana spinors do not exist.Comment: 16 pages, version to appear in J. Phys. A; AFK previously published
under the name A. F. Schunc
Reconstructing the two right-handed neutrino model
In this paper we propose a low-energy parametrization of the two right-handed
neutrino model, and discuss the prospects to determine experimentally these
parameters in supersymmetric scenarios. In addition, we present exact formulas
to reconstruct the high-energy leptonic superpotential in terms of the
low-energy observables. We also discuss limits of the three right-handed
neutrino model where this procedure applies.Comment: 28 pages, 4 figures. Typos corrected, references adde
Correlation entropy of synaptic input-output dynamics
The responses of synapses in the neocortex show highly stochastic and
nonlinear behavior. The microscopic dynamics underlying this behavior, and its
computational consequences during natural patterns of synaptic input, are not
explained by conventional macroscopic models of deterministic ensemble mean
dynamics. Here, we introduce the correlation entropy of the synaptic
input-output map as a measure of synaptic reliability which explicitly includes
the microscopic dynamics. Applying this to experimental data, we find that
cortical synapses show a low-dimensional chaos driven by the natural input
pattern.Comment: 7 pages, 6 Figures (7 figure files
Breather trapping and breather transmission in a DNA model with an interface
We study the dynamics of moving discrete breathers in an interfaced piecewise
DNA molecule.
This is a DNA chain in which all the base pairs are identical and there
exists an interface such that the base pairs dipole moments at each side are
oriented in opposite directions.
The Hamiltonian of the Peyrard--Bishop model is augmented with a term that
includes the dipole--dipole coupling between base pairs. Numerical simulations
show the existence of two dynamical regimes. If the translational kinetic
energy of a moving breather launched towards the interface is below a critical
value, it is trapped in a region around the interface collecting vibrational
energy. For an energy larger than the critical value, the breather is
transmitted and continues travelling along the double strand with lower
velocity. Reflection phenomena never occur.
The same study has been carried out when a single dipole is oriented in
opposite direction to the other ones.
When moving breathers collide with the single inverted dipole, the same
effects appear. These results emphasize the importance of this simple type of
local inhomogeneity as it creates a mechanism for the trapping of energy.
Finally, the simulations show that, under favorable conditions, several
launched moving breathers can be trapped successively at the interface region
producing an accumulation of vibrational energy. Moreover, an additional
colliding moving breather can produce a saturation of energy and a moving
breather with all the accumulated energy is transmitted to the chain.Comment: 15 pages, 11 figure
Continuous non-perturbative regularization of QED
We regularize in a continuous manner the path integral of QED by construction
of a non-local version of its action by means of a regularized form of Dirac's
functions. Since the action and the measure are both invariant under
the gauge group, this regularization scheme is intrinsically non-perturbative.
Despite the fact that the non-local action converges formally to the local one
as the cutoff goes to infinity, the regularized theory keeps trace of the
non-locality through the appearance of a quadratic divergence in the transverse
part of the polarization operator. This term which is uniquely defined by the
choice of the cutoff functions can be removed by a redefinition of the
regularized action. We notice that as for chiral fermions on the lattice, there
is an obstruction to construct a continuous and non ambiguous regularization in
four dimensions. With the help of the regularized equations of motion, we
calculate the one particle irreducible functions which are known to be
divergent by naive power counting at the one loop order.Comment: 23 pages, LaTeX, 5 Encapsulated Postscript figures. Improved and
revised version, to appear in Phys. Rev.
Ultraviolet Complete Electroweak Model Without a Higgs Particle
An electroweak model with running coupling constants described by an energy
dependent entire function is utraviolet complete and avoids unitarity
violations for energies above 1 TeV. The action contains no physical scalar
fields and no Higgs particle and the physical electroweak model fields are
local and satisfy microcausality. The and masses are compatible with a
symmetry breaking , which
retains a massless photon. The vertex couplings possess an energy scale
TeV predicting scattering amplitudes that can be tested at the
LHC.Comment: 19 pages, no figures, LaTex file. Equation and text corrected.
Reference added. Results remain the same. Final version published in European
Physics Journal Plus, 126 (2011
- …