# European Physical Journal Plus

Published by EDP Sciences

Online ISSN: 2190-5444

Published by EDP Sciences

Online ISSN: 2190-5444

Publications

In this paper, the properties of Cd(106-122)isotopes are considered in the
U(5)-SO(6)transitional region of IBM1. With employing a transitional
Hamiltonian which is based on affine SU(1,1)Lie Algebraic technique, the energy
levels and B(E2)transition rates are calculated. The results are compared with
the most recent experimental values where an acceptable degree of agreement is
achieved. Also, the energy ratios, control parameters and empirical two neutron
separation energies suggest spherical to gamma soft shape transitions in these
nuclei where the Cd (114,122)nuclei are considered as the best candidates for
the E(5)critical symmetry.

…

The Forbush decrease following the large X2 solar flare on mid-February 2011 has been observed by the muon telescopes of the
EEE Project, which are located in several Italian sites and at CERN. Data from two different telescopes of the EEE network
have been analyzed and compared to those measured by neutron monitor stations. The variation of the muon counting rate during
the Forbush decrease was also extracted for different intervals of the azimuthal angle of the incoming muons.

…

The Hilbert-Schmidt operator formulation of non-commutative quantum mechanics
in 2D Moyal plane is shown to allow one to construct Schwinger's SU(2)
generators. Using this the SU(2) symmetry aspect of both commutative and
non-commutative harmonic oscillator are studied and compared. Particularly, in
the non-commutative case we demonstrate the existence of a critical point in
the parameter space of mass and angular frequency where there is a manifest
SU(2) symmetry for a unphysical harmonic oscillator Hamiltonian built out of
commuting (unphysical yet covariantly transforming under SU(2)) position like
observable. The existence of this critical point is shown to be a novel aspect
in non-commutative harmonic oscillator, which is exploited to obtain the
spectrum and the observable mass and angular frequency parameters of the
physical oscillator-which is generically different from the bare parameters
occurring in the Hamiltonian. Finally, we show that a Zeeman term in the
Hamiltonian of non-commutative physical harmonic oscillator, is solely
responsible for both SU(2) and time reversal symmetry breaking.

…

In this article, we study the two-body strong decays of the bottom mesons
with the heavy meson effective theory in the leading order approximation, and
obtain all the analytical expressions of the decay widths of the light
pseudoscalar mesons transitions among the S-wave, P-wave and D-wave bottom
mesons. As an application, we tentatively assign the bottom meson $B(5970)$ as
the $2{\rm S}\,1^-$, $1{\rm D}\,1^-$ and $1{\rm D}\,3^-$ states, respectively,
and calculate the decay widths of the $B_1(5721)$, $B_2(5747)$, $B_{s1}(5830)$,
$B_{s2}(5840)$ and $B(5970)$, which can be confronted with the experimental
data in the future.

…

We develop a stochastic approach to study scalar field fluctuations of the
inflaton field in an early inflationary universe with a black-hole (BH), which
is described by an effective 4D SdS metric. Considering a 5D Ricci-flat SdS
static metric, we implement a planar coordinate transformation, in order to
obtain a 5D cosmological metric, from which the effective 4D SdS metric can be
induced on a 4D hypersurface. We found that at the end of inflation, the
squared fluctuations of the inflaton field are not exactly scale independent
and becomes sensitive with the mass of the BH.

…

We use the Bogoliubov formalism to study both, particles and gravitons
creation at the reheating epoch, after a phase transition from inflation to a
radiation dominated universe. The modes of the inflaton field fluctuations and
the scalar fluctuations of the metric at the end of inflation are obtained by
using a recently introduced formalism related to the Induced Matter theory of
gravity. The interesting result is that the number of created particles is
bigger than $10^{90}$ on cosmological scales. Furthermore, the number of
gravitons are nearly $10^{-17}$ times smaller than the number of created
particles. In both cases, these numbers rapidly increases on cosmological
scales.

…

We consider a five-dimensional Minimal Supersymmetric Standard Model
compactified on a S1/Z2 orbifold, and study the evolution of neutrino masses,
mixing angles and phases for different values of tan beta and different radii
of compactification. We consider the usual four dimensional Minimal
Supersymmetric Standard Model limit plus two extra-dimensional scenarios: where
all matter superfields can propagate in the bulk, and where they are
constrained to the brane. We discuss in both cases the evolution of the mass
spectrum, the implications for the mixing angles and the phases. We find that a
large variation for the Dirac phase is possible, which makes models predicting
maximal leptonic CP violation especially appealing.

…

The cross-section of the natPb binary fission, induced by 7Li ions at 245 MeV
energy, was measured and the fission product cross-sections studied by means of
activation analysis in the off-line regimen. The analysis of charge and mass
distributions of fission products allows to calculate the fission
cross-section. The recoil technique ("thick target- thick catcher"), based on
the two step model mathematical formalism, is used for the determination of the
kinematical characteristics of reaction products. The data concerning
transferred linear momentum provides information on the initial
projectile-target interaction, and is compared to measurements of the
proton-induced fission.

…

We present spectral distributions of channeling radiation by 20-800MeV electrons for various planes of a thin 4H polytype
silicon carbide crystal. The quantum theory of channeling radiation has been applied to calculate the transverse electron
states in the continuum potential of crystal planes and to study the transition energies, linewidths, depth dependences of
quantum states populations, and spectral radiation distributions. At electron energies higher than 100MeV the spectral distributions
of emitted radiation have been calculated within the classical approach, and compared successfully with the quantum mechanical
solutions. We discuss specific properties of planar channeling radiation in a 4H SiC polytype and find some new features of
electron channeling in 4H SiC not available in other structures.

…

We have derived the hierarchy of soliton equations associated with the
untwisted affine Kac-Moody algebra D^(1)_4 by calculating the corresponding
recursion operators. The Hamiltonian formulation of the equations from the
hierarchy is also considered. As an example we have explicitly presented the
first non-trivial member of the hierarchy, which is an one-parameter family of
mKdV equations. We have also considered the spectral properties of the Lax
operator and introduced a minimal set of scattering data.

…

We derive and calculate the space-time translational gauge identities in
quantum Yang-Mills gravity with a general class of gauge conditions involving
two arbitrary parameters. These identities of the Abelian group of translation
are a generalization of Ward-Takahasi-Fradkin identities and important for
general discussions of possible renormalization of Yang-Mills gravity with
translational gauge symmetry. The gauge identities in Yang-Mills gravity with a
general class of gauge conditions are substantiated by explicit calculations.

…

In the present work we analyze the old controversy of Abraham and Minkowski from the microscopic point of view, and from the
perspective of a momentum balance equation. Thus we complete the line of research on this subject initiated by Lai et al. (H.M. Lai, W.M. Suen, K. Young, Phys. Rev. A 25, 1755 (1982)). We find that a new term, -
\frac1c {\frac{{1}}{{c}}}
\frac¶m¶t {\frac{{\partial \mathbf{m}}}{{\partial t}}}×E , justified with several arguments, some of which founded in relativity theory, gives a more coherent view of the controversy.
As a test for this approach, we show that the Helmholtz force density may be obtained from a momentum balance equation derived
directly from Maxwell’s equations under certain approximations; we find with this analysis that rather than resolve the controversy,
we can dissolve it. That is, we have rather a problem of physical interpretation, since we show that other momentum balance
equations are also all legitimate implications of Maxwell’s equations.

…

A new kind of dark matter structures, ultracompact minihalos (UCMHs) was
proposed recently. They would be formed during the radiation dominated epoch if
the large density perturbations are existent. Moreover, if the dark matter is
made up of weakly interacting massive particles, the UCMHs can have effect on
cosmological evolution because of the high density and dark matter annihilation
within them. In this paper, one new parameter is introduced to consider the
contributions of UCMHs due to the dark matter annihilation to the evolution of
cosmology, and we use the current and future CMB observations to obtain the
constraint on the new parameter and then the abundance of UCMHs. The final
results are applicable for a wider range of dark matter parameters

…

The evolution of the universe in Brans-Dicke (BD) theory is discussed in this paper. Considering a parameterized scenario for BD scalar field φ = φ
0a
α
which plays the role of gravitational constant G, we apply the Markov Chain Monte Carlo method to investigate a global constraints on BD theory with a self-interacting potential according to the current observational data: the Union2 dataset of type-Ia supernovae (SNIa), the high-redshift Gamma-Ray Bursts (GRBs) data, the observational Hubble data (OHD), the cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and the cosmic microwave background (CMB) data. It is shown that an expanded universe from deceleration to acceleration is given in this theory, and the constraint results of dimensionless matter density Ω
0m
and parameter α are, Ω
0m
= 0.286
−0.039−0.047+0.037+0.050 and α = 0.0046
−0.0171−0.0206+0.0149+0.0171 which is consistent with the result of current experiment exploration, |α| ≤ 0.132124. In addition, we use the geometrical diagnostic method, jerk parameter j, to distinguish the BD theory and the cosmological constant model in Einstein’s theory of general relativity.

…

In the present work we have searched the existence of the late time
acceleration of the Universe. The matter source that is responsible for the
late time acceleration of the Universe consists of cosmic fluid with the
equation of state parameter $\omega =\frac{p}{\rho}$ and uniform magnetic field
of energy density $\rho_{B}$. The study is done here under the framework of
spatially homogeneous and anisotropic locally rotationally symmetric (LRS)
Bianchi-I cosmological model in the presence of magnetized dark energy. To get
the deterministic model of the Universe, we assume that the shear scalar
$(\sigma)$ in the model is proportional to expansion scalar $(\theta)$. This
condition leads to $A=B^{n}$, where $A$ and $B$ are metric functions and $n$ is
a positive constant giving the proportionality condition between shear and
expansion scalar. It has been found that the isotropic distribution of
magnetized dark energy leads to the present accelerated expansion of the
Universe and the derived model is in good agreement with the recent
astrophysical observations. The physical behavior of the Universe has been
discussed in details.

…

Plane symmetric cosmological models are investigated with or without any dark
energy components in the field equations. Keeping an eye on the recent
observational constraints concerning the accelerating phase of expansion of the
universe, the role of magnetic field is assessed. In the absence of dark energy
components, magnetic field can favour an accelerating model even if we take a
linear relationship between the directional Hubble parameters. In presence of
dark energy components in the form of a time varying cosmological constant, the
influence of magnetic field is found to be limited.

…

The role that small particle accelerators play in the field of applications to Cultural Heritage (for material analysis and
dating) is critically discussed also in comparison to other techniques, pointing out pros and cons. As to material analysis,
some peculiarities of ion beam techniques may be now less unique than they were perhaps ten years ago, but these techniques
can still reach unrivalled results thanks to a smart use of their potential: for instance, they can provide elemental maps
and resolve layer structures. Concerning Accelerator Mass Spectrometry, its unique performance for radiocarbon dating -- as
to sensitivity, precision and quasi non-destructivity -- is described, and perspectives for further improvements are presented.

…

We present a criterion for deciding which compact extra dimensional spaces
yield physically reliable Newton's law corrections. We study compact manifolds
with boundary and without boundary. The boundary conditions which we use on the
boundaries are Dirichlet or Neumann. We find that compact connected Riemannian
manifolds with Dirichlet boundaries are completely excluded as extra
dimensional spaces.

…

This paper presents a full derivation of the variance-to-mean or
Feynman-alpha formula in a two energy group and two spatial region-treatment.
The derivation is based on the Chapman - Kolmogorov equation with the inclusion
of all possible neutron reactions and passage intensities between the two
regions. In addition, the two-group one-region and the two-region one-group
Feynman-alpha formulas, treated earlier in the literature for special cases,
are extended for further types and positions of detectors.We focus on the
possibility of using these theories for accelerator-driven systems and
applications in the safeguards domain, such as the differential
self-interrogation method and the differential die-away method. This is due to
the fact that the predictions from the models which are currently used do not
fully describe all the effects in the heavily reflected fast or thermal
systems. Therefore, in conclusion a comparative study of the two-group
two-region, the two-group one-region, the one-group two-region and the
one-group one-region Feynman-alpha models is discussed.

…

In the geometric-optics limit, Yang-Mills gravity with space-time
translational gauge symmetry predicts $\D \phi =7Gm/(2R) \approx 1.53''$ for
the deflection of a light ray by the sun. The result, which is about 12%
smaller than that in the conventional theory, is consistent with experiments
involving optical frequencies that had an accuracy of 10-20%.

…

Bogoliubov pseudoparticle creation in a BEC undergoing a WH like flow is
investigated analytically in the case of a one dimensional geometry with
stepwise homogeneous regions. Comparison of the results with those
corresponding to a BH flow is performed. The implications for the analogous
gravitational problem is discussed.

…

Using the standard reductive perturbation technique, a nonlinear cubic complex Ginzburg-Landau equation (CGL3) is derived to study the modulational instability of ion acoustic waves (IAWs) in an unmagnetized plasma consisting of warm adiabatic ions and non-thermal electrons, which form the background. The CGL3 is exactly solved by using two methods: the separation of variables and the complex tanh function which produces four solutions; the results are compared and good agreement exists in most predictions. The CGL3 admits localized envelope (solitary wave) solutions of bright and dark types. We study the effects of the thermal conductivity of ions and non-thermally distributed electrons \( \beta\) on the modulational stability. The effect of ion thermal conductivity makes the frequency \( \omega\) be complex in the nonlinear dispersion relation. In terms of the first mode \( \omega_{{1}}^{}\) , the amplitude of the wave moving in the (+ ve) x -direction decreases when any one of the parameters \( \beta\) and the temperature ratio \( \sigma\) (= T
i/T
eff) increases (where Teff and Ti are the effective and ion temperatures, respectively). It is found that the whole k -\( \sigma\) plane transforms to an unstable region as \( \beta\)
\( \approx\) 0.85 . Referring to the internal energy formula, the order of magnitude ratios of different kinds and contributions of the internal energy changes are calculated for various sets {\( \sigma\),\( \beta\)} . The obtained results encourage us to name the unstable system --which experiences loss and gain of ions escaping out or embedding themselves into the acoustic frequency domain, collision and recently experimentally due to ionization and deionization-- a non-equilibrium thermodynamic dissipative open IAW system.

…

General two-particle system is considered within the formalism of Fokker-type
action integrals. It is assumed that the system is invariant with respect to
the Aristotle group which is a common subgroup of the Galileo and Poincar\'e
groups. It is shown that equations of motion of such system admit circular
orbit solutions. The dynamics of perturbations of these solutions is studied.
It is described by means of a linear homogeneous set of time-nonlocal equations
and is analyzed in terms of eigenfrequencies and eigenmodes. The Hamiltonian
description of the system is built in the almost circular orbit approximation.
The Aristotle-invariance of the system is exploit to avoid a double count of
degrees of freedom and to select physical modes. The quantization procedure and
a construction of energy spectrum of the system is proposed.

…

A method of calculation for the constrained variational derivatives for
gravitational actions in the pseudo-Riemannian case is proposed as a practical
variant of the first order formalism with constraints. The proposed method
calculation is then used to derive the metric field equations for generic
$f(R)$ model.

…

An open issue in classical relativistic mechanics is the consistent treatment
of the dynamics of classical $N$-body systems of mutually-interacting
particles. This refers, in particular, to charged particles subject to EM
interactions, including both binary and self interactions (EM-interacting
$N$-body systems). In this paper it is shown that such a description can be
consistently obtained in the context of classical electrodynamics, for the case
of a $N$-body system of classical finite-size charged particles. A variational
formulation of the problem is presented, based on the $N$-body hybrid
synchronous Hamilton variational principle. Covariant Lagrangian and
Hamiltonian equations of motion for the dynamics of the interacting $N$-body
system are derived, which are proved to be delay-type ODEs. Then, a
representation in both standard Lagrangian and Hamiltonian forms is proved to
hold, the latter expressed by means of classical Poisson Brackets. The theory
developed retains both the covariance with respect to the Lorentz group and the
exact Hamiltonian structure of the problem, which is shown to be intrinsically
non-local. Different applications of the theory are investigated. The first one
concerns the development of a suitable Hamiltonian approximation of the exact
equations that retains finite delay-time effects characteristic of the binary
and self EM interactions. Second, basic consequences concerning the validity of
Dirac generator formalism are pointed out, with particular reference to the
instant-form representation of Poincar\`{e} generators. Finally, a discussion
is presented both on the validity and possible extension of the Dirac generator
formalism as well as the failure of the so-called Currie \textquotedblleft
no-interaction\textquotedblright\ theorem for the non-local Hamiltonian system
considered here.

…

A viscous incompressible electrically conducting fluid flow through a porous medium over a stretching sheet is considered
in the presence of a magnetic field. Such flow problems have relevance in the process of a polymer sheet extrusion from a
dye, and the numerical and approximate solutions of these problems are of great interest as these solutions serve practical
purposes. By using the technique of stretching variables of the flow concern in porous medium and minimizing the residual
of the resulting governing differential equations by the least squares method, we obtained an approximate solution for this
problem of flow through porous medium near a stretching sheet. The results are also compared to a numerical solution determined
by using the shooting method along with the Runge-Kutta method. The effects of various pertinent parameters on the velocity
distribution and the residual function are investigated. The results are depicted graphically and discussed.

…

In this work we obtain the Landau levels and the Hall conductivity at zero
temperature of a two-dimensional electron gas on a conical surface. We
investigate the integer quantum Hall effect considering two different
approaches. The first one is an extrinsic approach which employs an effective
scalar potential that contains both the Gaussian and the mean curvature of the
surface. The second one, an intrinsic approach where the Gaussian curvature is
the sole term in the scalar curvature potential. From a theoretical point of
view, the singular Gaussian curvature of the cone may affect the wave functions
and the respective Landau levels. Since this problem requests {\it self-adjoint
extensions}, we investigate how the conical tip could influence the integer
quantum Hall effect, comparing with the case were the coupling between the wave
functions and the conical tip is ignored. This last case corresponds to the
so-called {\it Friedrichs extension}. In all cases, the Hall conductivity is
enhanced by the conical geometry depending on the opening angle. There are a
considerable number of theoretical papers concerned with the self-adjoint
extensions on a cone and now we hope the work addressed here inspires
experimental investigation on these questions about quantum dynamics on a cone.

…

In this note we address the well-known cosmic coincidence problem in the
framework of the \textit{f(R,T)} gravity. In order to achieve this, an
interaction between dark energy and dark matter is considered. A constraint
equation is obtained which filters the \textit{f(R,T)} models that produce a
stationary scenario between dark energy and dark matter. Due to the absence of
a universally accepted interaction term introduced by a fundamental theory, the
study is conducted over three different forms of chosen interaction terms. As
an illustration three widely known models of \textit{f(R,T)} gravity are taken
into consideration and used in the setup designed to study the problem. The
study reveals that, the realization of the coincidence scenario is almost
impossible for the popular models of $f(R,T)$ gravity, thus proving to be a
major setback for these models.

…

We obtain a new solution of the Einstein-anti-Maxwell theory with
cosmological constant, called anti-Reissner-Nordstrom-(A)de Sitter
(anti-RN-(A)dS) solution. The basic properties of this solution is reviewed.
Its thermodynamics is consistently established, with the extreme cases and
phase transitions, where the analysis is performed through two methods, the
usual one and that of Geometrothermodynamics . The Geometrothermodynamics
analysis does not provide a result in agreement with the usual method or by the
specific heat. We establish local and global thermodynamic stabilities of
anti-RN-AdS solution through the specific heat and the canonical and
grand-canonical ensembles.

…

The Pierre Auger Observatory detects the highest energy cosmic rays.
Calorimetric measurements of extensive air showers induced by cosmic rays are
performed with a fluorescence detector. Thus, one of the main challenges is the
atmospheric monitoring, especially for aerosols in suspension in the
atmosphere. Several methods are described which have been developed to measure
the aerosol optical depth profile and aerosol phase function, using lasers and
other light sources as recorded by the fluorescence detector. The origin of
atmospheric aerosols traveling through the Auger site is also presented,
highlighting the effect of surrounding areas to atmospheric properties. In the
aim to extend the Pierre Auger Observatory to an atmospheric research platform,
a discussion about a collaborative project is presented.

…

We briefly describe the modified Friedmann equations for Einstein-Aether
gravity theory and we find the effective density and pressure. The purpose of
our present work is to reconstruction of Einstein-Aether Gravity from other
modified gravities like $f(T)$, $f(R)$, $f(G)$, $f(R,T)$ and $f(R,G)$ and check
its viability. The scale factor is chosen in power law form. The free function
$F(K)$ for Einstein-Aether gravity (where $K$ is proportional to $H^{2}$) have
been found in terms for $K$ by the correspondence between Einstein-Aether
gravity and other modified gravities and the nature of $F(K)$ vs $K$ have been
shown graphically for every cases. Finally, we analyzed the stability of each
reconstructed Einstein-Aether gravity model.

…

In this work we investigate the background dynamics when dark energy is
coupled to dark matter with a suitable interaction in the universe described by
Einstein-Aether gravity. Dark energy in the form of Modified Chaplygin gas is
considered. A suitable interaction between dark energy and dark matter is
considered in order to at least alleviate (if not solve) the cosmic coincidence
problem. The dynamical system of equations is solved numerically and a stable
scaling solution is obtained. A significant attempt towards the solution of the
cosmic coincidence problem is taken. The statefinder parameters are also
calculated to classify the dark energy models. Graphs and phase diagrams are
drawn to study the variations of these parameters. It is also seen that the
background dynamics of modified Chaplygin gas in Einstein-Aether gravity is
completely consistent with the notion of an accelerated expansion in the late
universe. Finally, it has been shown that the universe follows the power law
form of expansion around the critical point.

…

Understanding the role of microenvironment in cancer growth and metastasis is
a key issue for cancer research. Here, we study the effect of osmotic pressure
on the functional properties of primary and metastatic melanoma cell lines. In
particular, we experimentally quantify individual cell motility and
transmigration capability. We then perform a circular scratch assay to study
how a cancer cell front invades an empty space. Our results show that primary
melanoma cells are sensitive to a low osmotic pressure, while metastatic cells
are less. To better understand the experimental results, we introduce and study
a continuous model for the dynamics of a cell layer and a stochastic discrete
model for cell proliferation and diffusion. The two models capture essential
features of the experimental results and allow to make predictions for a wide
range of experimentally measurable parameters.

…

The essentially unique torsionful version of the classical two-component
spinor formalisms of Infeld and van der Waerden is exhibited. All the metric
spinors and connecting objects that arise here are formally the same as the
ones borne by the traditional formalisms. Any spin-affine connection appears to
possess a torsional part which is conveniently taken as a suitable asymmetric
contribution. Such a torsional affine contribution thus supplies a
gauge-invariant potential that may carry an observable character, and thereby
effectively takes over the role of any trivially realizable symmetric
contribution. The overall curvature spinors for any spin-affine connection
accordingly emerge from the irreducible decomposition of a mixed world-spin
object which in turn comes out of the action on elementary spinors of a typical
torsionful second-order covariant derivative operator. It is pointed out that
the new theoretical framework supposedly should afford both a physical
characterization of the cosmic dark energy and a description of the propagation
of gravitons in torsional regions of the universe.

…

In this paper we study the dynamics of the late Universe when a nonminimally coupled Higgs field is present. In general, the nonminimal coupling leads to a nontrivial mixing between the gravitational degrees of freedom and the Goldstone massless bosons. We know that this is irrelevant during the inflationary phase. In contrast, in the late Universe the nonminimal coupling affects the classical equations of motion, leading to an acceleration of the expansion rate or to a collapse that forms Q-balls. © 2014 Società Italiana di Fisica and Springer-Verlag Berlin Heidelberg.

…

We present a class of models where both the primordial inflation and the late
times de Sitter phase are driven by simple phenomenological agegraphic
potentials. In this context, a possible new scenario for a smooth exit from
inflation to the radiation era is discussed by resorting the kination (stiff)
era but without the inefficient radiation production mechanism of these models.
This is done by considering rapidly decreasing expressions for $V(t)$ soon
after inflation. We show that the parameters of our models can reproduce the
scalar spectral parameter $n_s$ predicted by Planck data in particular for
models with concave potentials.

…

In this paper, we investigate the twisted algebra of the fermionic
oscillators associated with Dirac field defined in $\kappa$-Minkowski
space-time. Starting from $\kappa$-deformed Dirac theory, which is invariant
under the undeformed $\kappa$-Poincare algebra, using the twisted flip
operator, we derive the deformed algebra of the creation and annihilation
operators corresponding to the Dirac field quanta in $\kappa$-Minkowski
space-time. In the limit $a\rightarrow 0$, the deformed algebra reduces to the
commutative result.

…

VSR symmetries are here naturally incorporated in the DKP algebra on the spin-0 and the spin- 1 DKP sectors. We show that the Elko (dark) spinor fields structure plays an essential role in accomplishing this aim, unravelling hidden symmetries on the bosonic DKP fields under the action of discrete symmetries.

…

In this paper various representations of the exceptional Lie algebra G_2 are
investigated in a purely algebraic manner, and multi-boson/multi-fermion
realizations are obtained. Matrix elements of the master representation, which
is defined on the space of the universal enveloping algebra of G_2, are
explicitly determined. From this master representation, different
indecomposable representations defined on invariant subspaces or quotient
spaces with respect to these invariant subspaces are discussed. Especially, the
elementary representations of G_2 are investigated in detail, and the
corresponding six-boson realization is given. After obtaining explicit forms of
all twelve extremal vectors of the elementary representation with the highest
weight {\Lambda}, all representations with their respective highest weights
related to {\Lambda} are systematically discussed. For one of these
representations the corresponding five-boson realization is constructed.
Moreover, a new three-fermion realization from the fundamental representation
(0,1) of G_2 is constructed also.

…

A stochastic theory for a branching process in a neutron population with two
energy levels is used to assess the applicability of the differential
self-interrogation Feynman-alpha method by numerically estimated reaction
intensities from Monte Carlo simulations. More specifically, the variance to
mean or Feynman-alpha formula is applied to investigate the appearing
exponentials using the numerically obtained reaction intensities.

…

A Feynman-alpha formula has been derived in a two region domain pertaining
the stochastic differential self-interrogation (DDSI) method and the
differential die-away method (DDAA). Monte Carlo simulations have been used to
assess the applicability of the variance to mean through determination of the
physical reaction intensities of the physical processes in the two domains.
More specifically, the branching processes of the neutrons in the two regions
are described by the Chapman - Kolmogorov equation, including all reaction
intensities for the various processes, that is used to derive a variance to
mean relation for the process. The applicability of the Feynman-alpha or
variance to mean formulae are assessed in DDSI and DDAA of spent fuel
configurations.

…

The von Neumann entropy of a generic quantum state is not unique unless the
state can be uniquely decomposed as a sum of extremal or pure states. As
pointed out to us by Sorkin, this happens if the GNS representation (of the
algebra of observables in some quantum state) is reducible, and some
representations in the decomposition occur with non-trivial degeneracy. This
non-unique entropy can occur at zero temperature. We will argue elsewhere in
detail that the degeneracies in the GNS representation can be interpreted as an
emergent broken gauge symmetry, and play an important role in the analysis of
emergent entropy due to non-Abelian anomalies. Finally, we establish the
analogue of an H-theorem for this entropy by showing that its evolution is
Markovian, determined by a stochastic matrix.

…

We show how power-law corrections to the Einstein-Hilbert action yield a
viable extended theory of gravity, passing the Solar-System tests, provided
that the power-law exponent n is strictly comprised between 2 and 3. We
implement this paradigm on a cosmological setting outlining how the main phases
of the Universe thermal history are properly reproduced. As a result, we find
two distinct constraints on the characteristic length scale of the model, i.e.,
a lower bound from the Solar-System test and an upper bound found by requiring
the existence of the matter-dominated phase of the Universe evolution. We also
show how the extended framework can accommodate the existence of an early de
Sitter phase. Within the allowed range of characteristic length scales, the
relation between the expansion rate H_I and the energy scale M of inflation is
modified, yielding a value of H_I several orders of magnitude smaller than the
one found in the standard picture, i.e., H_I ~ M^2/m_pl. The observational
implication of this fact is that, quite generally, a tiny value of the
tensor-to-scalar ratio r is expected in the extended framework, that will go
undetected even by future missions focused on cosmic microwave background
polarization, like CMBPol. The suppression of primordial tensor modes also
implies that the inflationary scale can be made arbitrarily close to the Planck
one without spoiling the current limits on r. Finally, considering the same
modified action, an analysis of the propagation of gravitational waves on a
Robertson-Walker background is addressed. We find that, in the allowed
parameter range, the f(R) correction does not significantly affect the standard
evolution.

…

Resonances, which are also described as autoionizing or quasi-bound states,
play an important role in the scattering of atoms and ions with electrons. The
current article is an overview of the main methods, including a
recently-proposed one, that are used to find and analyze resonances.

…

We analyse the $\theta$-angle physics associated to extensions of the
standard model of particle interactions featuring new strongly coupled sectors.
We start by providing a pedagogical review of the $\theta$-angle physics for
Quantum Chromodynamics (QCD) including also the axion properties. We then move
to analyse composite extensions of the standard model elucidating the interplay
between the new $\theta$-angle with the QCD one. We consider first QCD-like
dynamics and then generalise it to consider several kinds of new strongly
coupled gauge theories with fermions transforming according to different matter
representations. Our analysis is of immediate use for different models of
composite Higgs dynamics, composite dark matter and inflation.

…

We decompose the canonical SEM tensor of the electrodynamics, in the presence of sources, into a part corresponding to the
Maxwell-Minkowski tensor and into another part that is non-symmetric. From the latter, we derive a linear momentum density
and we write the conservation law of the total linear momentum. Then, we derive an angular momentum, using the density of
the linear momentum calculated before. Doing so, some terms that, thereafter, will cancel each other with terms related to
the lack of symmetry of the canonical tensor, appear. Lastly, we prove that the same expression for the conservation of the
total angular momentum is obtained either from the canonical tensor or from the Maxwell-Minkowski tensor. The aspects of GR
and of quantization will not be considered here.

…

Coherent pion production by neutrinos has been interpreted in the framework
of the Partially Conserved Axial Current hypothesis (PCAC) and explicit model
calculations are available. In this article we compute angular correlations for
the produced pions which may help to separate the signal from the background.
We present many figures useful for the experiments and compare them with
another model.

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There are no phase-space trajectories for anharmonic quantum systems, but Wigner’s phase-space
representation of quantum mechanics features Wigner current J . This current reveals fine details
of quantum dynamics – finer than is ordinarily thought accessible according to quantum folklore
invoking Heisenberg’s uncertainty principle. Here, we focus on the simplest, most intuitive, and
analytically accessible aspects of J . We investigate features of J for bound states of time-reversible,
weakly-anharmonic one-dimensional quantum-mechanical systems which are weakly-excited. We
establish that weakly-anharmonic potentials can be grouped into three distinct classes: hard, soft,
and odd potentials. We stress connections between each other and the harmonic case. We show
that their Wigner current fieldline patterns can be characterised by J ’s discrete stagnation points,
how these arise and how a quantum system’s dynamics is constrained by the stagnation points’
topological charge conservation. We additionally show that quantum dynamics in phase space, in
the case of vanishing Planck constant h̄ or vanishing anharmonicity, does not pointwise converge to
classical dynamics.

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Exact solutions of the totally anisotropic Bianchi type-II space-time are obtained in the scalar-tensor theories developed
by Saez and Ballester (Phys. Lett. A,113 (1985) 467) and Lau and Prokhovnik (Aust. J. Phys.,39 (1986) 339). The dynamical behaviour of these models has also been discussed.

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Spatially homogeneous but totally anisotropic and non-flat Bianchi type II
cosmological model has been studied in general relativity in the presence of
two minimally interacting fluids; a perfect fluid as the matter fluid and a
hypothetical anisotropic fluid as the dark energy fluid. The Einstein's field
equations have been solved by applying two kinematical ans\"{a}tze: we have
assumed the variation law for the mean Hubble parameter that yields a constant
value of deceleration parameter, and one of the components of the shear tensor
has been considered proportional to the mean Hubble parameter. We have
particularly dwelled on the accelerating models with non-divergent expansion
anisotropy as the Universe evolves. Yielding anisotropic pressure, the fluid we
consider in the context of dark energy, can produce results that can be
produced in the presence of isotropic fluid in accordance with the \Lambda CDM
cosmology. However, the derived model gives additional opportunities by being
able to allow kinematics that cannot be produced in the presence of fluids that
yield only isotropic pressure. We have obtained well behaving cases where the
anisotropy of the expansion and the anisotropy of the fluid converge to finite
values (include zero) in the late Universe. We have also showed that although
the metric we consider is totally anisotropic, the anisotropy of the dark
energy is constrained to be axially symmetric, as long as the overall energy
momentum tensor possesses zero shear stress.

…

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