1,184 research outputs found
On the relation between boundary proposals and hidden symmetries of the extended pre-big bang quantum cosmology
A framework associating quantum cosmological boundary conditions to
minisuperspace hidden symmetries has been introduced in \cite{7}. The scope of
the application was, notwithstanding the novelty, restrictive because it lacked
a discussion involving realistic matter fields. Therefore, in the herein
letter, we extend the framework scope to encompass elements from a
scalar-tensor theory in the presence of a cosmological constant. More
precisely, it is shown that hidden minisuperspace symmetries present in a
pre-big bang model suggest a process from which boundary conditions can be
selected.Comment: 15 pages, no figures, to appear in European Physical Journal
On the Schur multipliers of Lie superalgebras of maximal class
Let be a non-abelian nilpotent Lie superalgebra of dimensiom .
Nayak shows there is a non-negative such that
. Here we intend that
classify all non-abelian nilpotent Lie superalgebras, when .
Moreover, we classify the structure of all Lie superalgebras of dimension at
most such that
Subgroup Theorems for the -invariant of groups
U. Jezernik and P. Moravec have shown that if is a finite group with a
subgroup of index , then nth power of the Bogomolov multiplier of ,
is isomorphic to a subgroup of . In this
paper we want to prove a similar result for the center by center by variety
of groups, where is any outer commutator word
Factorization approach to generalized Dirac oscillators
We study generalized Dirac oscillators with complex interactions in (1+1) dimensions. It is shown that for the choice of interactions considered here, the Dirac Hamiltonians are pseudo Hermitian with respect to certain metric operators. Exact solutions of the generalized Dirac Oscillator for some choices of the interactions have also been obtained. It is also shown that generalized Dirac oscillators can be identified with Anti Jaynes Cummings type model and by spin flip it can also be identified with Jaynes Cummings type model
On characterisations of the input to state stability properties for conformable fractional order bilinear systems
This paper proposes for the first time the theoretical requirements that a fractional-order bilinear system with conformable derivative has to fulfil in order to satisfy different input-to-state stability (ISS) properties. Variants of ISS, namely ISS itself, integral ISS, exponential integral ISS, small-gain ISS, and strong integral ISS for the general class of conformable fractional-order bilinear systems are investigated providing a set of necessary and sufficient conditions for their existence and then compared. Finally, the correctness of the obtained theoretical results is verified by numerical example
A fingerprint based metric for measuring similarities of crystalline structures
Measuring similarities/dissimilarities between atomic structures is important
for the exploration of potential energy landscapes. However, the cell vectors
together with the coordinates of the atoms, which are generally used to
describe periodic systems, are quantities not suitable as fingerprints to
distinguish structures. Based on a characterization of the local environment of
all atoms in a cell we introduce crystal fingerprints that can be calculated
easily and allow to define configurational distances between crystalline
structures that satisfy the mathematical properties of a metric. This distance
between two configurations is a measure of their similarity/dissimilarity and
it allows in particular to distinguish structures. The new method is an useful
tool within various energy landscape exploration schemes, such as minima
hopping, random search, swarm intelligence algorithms and high-throughput
screenings
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