pinecone/core-2020-05-10-deduplication huggingface dataset:
Hubble Parameter in QCD Universe for finite Bulk Viscosity

We consider the influence of the perturbative bulk viscosity on the evolution
of the Hubble parameter in the QCD era of the early Universe. For the geometry
of the Universe we assume the homogeneous and isotropic
Friedmann-Lemaitre-Robertson-Walker metric, while the background matter is
assumed to be characterized by barotropic equations of state, obtained from
recent lattice QCD simulations, and heavy--ion collisions, respectively. Taking
into account a perturbative form for the bulk viscosity coefficient, we obtain
the evolution of the Hubble parameter, and we compare it with its evolution for
an ideal (non-viscous) cosmological matter. A numerical solution for the
viscous QCD plasma in the framework of the causal Israel-Stewart thermodynamics
is also obtained. Both the perturbative approach and the numerical solution
qualitatively agree in reproducing the viscous corrections to the Hubble
parameter, which in the viscous case turns out to be slightly different as
compared to the non--viscous case. Our results are strictly limited within a
very narrow temperature- or time-interval in the QCD era, where the quark-gluon
plasma is likely dominant.Comment: 9 pages (revtex4 style), 5 figures with 8 eps graph
The maximal acceleration, Extended Relativistic Dynamics and Doppler
  type shift for an accelerated source

Based on the generalized principle of relativity and the ensuing symmetry, we
have shown that there are only two possible types of transformations between
uniformly accelerated systems. The first allowable type of transformation holds
if and only if the Clock Hypothesis is true. If the Clock Hypothesis is not
true, the transformation is of Lorentz-type and implies the existence of a
universal maximal acceleration $a_m$.
  We present an extension of relativistic dynamics for which all admissible
solutions will have have a speed bounded by the speed of light $c$ and the
acceleration bounded by $a_m$. An additional Doppler type shift for an
accelerated source is predicted. The formulas for such shift are the same as
for the usual Doppler shift with $v/c$ replaced by $a/a_m$.
  The W. K\"{u}ndig experiment of measurement of the transverse Doppler shift
in an accelerated system was also exposed to a longtitudal shift due to the
acceleration. This experiment, as reanalyzed by Kholmetskii et al, shows that
the Clock Hypothesis is not valid. Based on the results of this experiment, we
predict that the value of the maximal acceleration $a_m$ is of the order
$10^{19}m/s^2$. Moreover, our analysis provides a way to measure experimentally
the maximal acceleration with existing technology.Comment: 10 pages, 1 figur
The non-birefringent limit of all linear, skewonless media and its
  unique light-cone structure

Based on a recent work by Schuller et al., a geometric representation of all
skewonless, non-birefringent, linear media is obtained. The derived
constitutive law is based on a "core", encoding the optical metric up to a
constant. All further corrections are provided by two (anti-)selfdual
bivectors, and an "axion". The bivectors are found to vanish if the optical
metric has signature (3,1) - that is, if the Fresnel equation is hyperbolic. We
propose applications of this result in the context of transformation optics and
premetric electrodynamics.Comment: 12 pages, REVTeX; v2: typos; v3: relevant changes in text,
  reorganization of manuscript; v4: new section added, final version, to appear
  in Annalen der Physi
On the multi-orbital band structure and itinerant magnetism of
  iron-based superconductors

This paper explains the multi-orbital band structures and itinerant magnetism
of the iron-pnictide and chalcogenides. We first describe the generic band
structure of an isolated FeAs layer. Use of its Abelian glide-mirror group
allows us to reduce the primitive cell to one FeAs unit. From
density-functional theory, we generate the set of eight Fe $d$ and As $p$
localized Wannier functions for LaOFeAs and their tight-binding (TB)
Hamiltonian, $h(k)$. We discuss the topology of the bands, i.e. allowed and
avoided crossings, the origin of the d6 pseudogap, as well as the role of the
As $p$ orbitals and the elongation of the FeAs$_{4}$ tetrahedron. We then
couple the layers, mainly via interlayer hopping between As $p_{z}$ orbitals,
and give the formalism for simple and body-centered tetragonal stackings. This
allows us to explain the material-specific 3D band structures. Due to the high
symmetry, several level inversions take place as functions of $k_{z}$ or
pressure, resulting in linear band dispersions (Dirac cones). The underlying
symmetry elements are, however, easily broken, so that the Dirac points are not
protected, nor pinned to the Fermi level. From the paramagnetic TB Hamiltonian,
we form the band structures for spin spirals with wavevector $q$ by coupling
$h(k)$ and $h (k+q)$. The band structure for stripe order is studied as a
function of the exchange potential, $\Delta$, using Stoner theory. Gapping of
the Fermi surface (FS) for small $\Delta $ requires matching of FS dimensions
(nesting) and $d$-orbital characters. The origin of the propeller-shaped FS is
explained. Finally, we express the magnetic energy as the sum over
band-structure energies, which enables us to understand to what extent the
magnetic energies might be described by a Heisenberg Hamiltonian, and the
interplay between the magnetic moment and the elongation of the FeAs4
tetrahedron
Cosmological constant from quarks and torsion

We present a simple and natural way to derive the observed small, positive
cosmological constant from the gravitational interaction of condensing
fermions. In the Riemann-Cartan spacetime, torsion gives rise to the
axial-axial four-fermion interaction term in the Dirac Lagrangian for spinor
fields. We show that this nonlinear term acts like a cosmological constant if
these fields have a nonzero vacuum expectation value. For quark fields in QCD,
such a torsion-induced cosmological constant is positive and its energy scale
is only about 8 times larger than the observed value. Adding leptons to this
picture could lower this scale to the observed value.Comment: 4 pages; published versio
Dmitrij Volkov, super-Poincare group and Grassmann variables

A fundamental role of the Hermann Grassmann anticommuting variables both in
physics and mathematics is discussed on the example of supersymmetry. The talk
describes how the D. Volkov question about possibility of the existence of
Nambu-Goldstone fermions, realized by the Grassmannian variables, resulted in
the discovery of the super-Poincare group, its spontaneous breaking and
gauging.Comment: 9 pages, corrected version published in Annalen der Physik, invited
  talk at the Grassmannian Conference in Fundamental Cosmology, Szczecin, 14-19
  September 200
Metric-affine $f(R)$-gravity with torsion: an overview

Torsion and curvature could play a fundamental role in explaining
cosmological dynamics. f(R)-gravity with torsion is an approach aimed to
encompass in a comprehensive scheme all the Dark Side of the Universe (Dark
Energy and Dark Matter). We discuss the field equations in empty space and in
presence of perfect fluid matter taking into account the analogy with the
metric-affine formalism. The result is that the extra curvature and torsion
degrees of freedom can be dealt under the standard of an effective scalar field
of fully geometric origin. The initial value problem for such theories is also
discussed.Comment: 10 pages, Grassmann Meeting 2009, Annalen der Physi
Algebraic Geometry Approach in Gravity Theory and New Relations between
  the Parameters in Type I Low-Energy String Theory Action in Theories with
  Extra Dimensions

On the base of the distinction between covariant and contravariant metric
tensor components, a new (multivariable) cubic algebraic equation for
reparametrization invariance of the gravitational Lagrangian has been derived
and parametrized with complicated non - elliptic functions, depending on the
(elliptic) Weierstrass function and its derivative. This is different from
standard algebraic geometry, where only two-dimensional cubic equations are
parametrized with elliptic functions and not multivariable ones.
  Physical applications of the approach have been considered in reference to
theories with extra dimensions. The s.c. "length function" l(x) has been
introduced and found as a solution of quasilinear differential equations in
partial derivatives for two different cases of "compactification + rescaling"
and "rescaling + compactification". New physically important relations
(inequalities) between the parameters in the action are established, which
cannot be derived in the case $l=1$ of the standard gravitational theory, but
should be fulfilled also for that case.Comment: 4 pages; no figures; Talk at the Grassmannian Conference in
  Fundamental Cosmology "Grasscosmofun'09" (14-19 September 2009, University of
  Szczecin, Poland); prepared for the Proceedings of the Conference, which will
  appear in a special issue of the journal "Annalen der Physik" (Leipzig);
  "Ann.der Phys." style files use
Non-standard loop quantum cosmology

We present results concerning the nature of the cosmological big bounce(BB)
transition within the loop geometry underlying loop quantum cosmology (LQC).
Our canonical quantization method is an alternative to the standard LQC. An
evolution parameter we use has clear interpretation both at classical and
quantum levels. The physical volume operator has discrete spectrum which is
bounded from below. The minimum gap in the spectrum defines a quantum of the
volume. The spectra of operators are parametrized by a free parameter to be
determined.Comment: 4 pages, prepared for the proceedings of the Grassmannian Conference
  in Fundamental Cosmology (Grasscosmofun'09), 14-19 September 2009, Szczecin,
  Polan
Dark energy from quantum fluctuations

We have derived the quantum vacuum pressure P_vac as a primary entity,
removing a trivial and a gauge terms from the cosmological constant-like part
(the zeroth term) of the effective action for a free matter field. The quantum
vacuum energy density G_vac appears a secondary entity, but both are of
expected order. Moreover P_vac and G_vac are dynamical, and therefore they can
be used in the Einstein equations. In particular, they could dynamically
support holographic dark energy model as well as the `thermodynamic' one.Comment: 4 pages (in AdP style), 2 references added, prepared for the
  proceedings of the Grassmannian Conference in Fundamental Cosmology
  (Grasscosmofun'09), 14-19 September 2009, Szczecin, Polan
Three steps to accelerated expansion

We study the dynamics of a non-minimally coupled scalar field cosmology with
a potential function. We use the framework of dynamical systems theory to
investigate all evolutional paths admissible for all initial conditions.
Additionally, we assume the presence of barotropic matter and show that the
dynamics can be formulated in terms of an autonomous dynamical system. We have
found fixed points corresponding to three main stages of the evolution of the
universe, namely, radiation, matter and quintessence domination epochs. Using
the linearization of the dynamical systems in the vicinity of the critical
points we explicitly obtain formulas determining the effective equation of
state parameter for the universe at different epochs. In our approach the form
of $w(z)$ parametrisation is derived directly from the dynamical equations
rather than postulated {\it a priori}.Comment: 4 pages, 1 fig; w-art.cls; prepared for the proceedings of The
  Grassmannian Conference in Fundamental Cosmology "Grasscosmofun'09" (14-19
  September, 2009), University of Szczecin, Polan
Statistical anisotropy as a consequence of inflation

Cosmological inflation remains to be a unique mechanism of generation of
plausible initial conditions in the early universe. In particular, it generates
the primordial quasiclassical perturbations with power spectrum determined by
the fundamental principles of quantum field theory. In this work, we pay
attention to the fact that the quasiclassical perturbations permanently
generated at early stages of inflation break homogeneity and isotropy of the
cosmological background. The evolution of the small-scale quantum vacuum modes
on this inhomogeneous background results in statistical anisotropy of the
primordial power spectrum, which can manifest itself in the observable
large-scale structure and cosmic microwave background. The effect is predicted
to have almost scale-invariant form dominated by a quadrupole and may serve as
a non-trivial test of the inflationary scenario. Theoretical expectation of the
magnitude of this statistical anisotropy depends on the assumptions about the
physics in the trans-Planckian region of wavenumbers.Comment: 7 pages, Proceedings of the Grassmannian Conference in Fundamental
  Cosmology, September 14--19, 2009, Szczecin, Polan
On the fate of vacuum bubbles on matter backgrounds

In this letter we discuss cosmological first order phase transitions with de
Sitter bubbles nucleating on (inhomogeneous) matter backgrounds. The de Sitter
bubble can be a toy model for an inflationary phase of universes like our own.
Using the thin wall approximation and the Israel junction method we trace the
classical evolution of the formed bubbles within a compound model. We first
address homogeneous ambient space (FRW model) and already find that bubbles
nucleated in a dust dominated background cannot expand. For an inhomogeneous
dust background (LTB model) we describe cases with at least initially expanding
bubbles. Yet, an ensuing passage of the bubble wall through ambient curvature
inhomogeneities remains unnoticed for observers inside the bubble. Notable
effects also for interior observers are found in the case of a rapid background
phase transition in a FRW model.Comment: 4 pages, 2 figures, proceedings (Annalen der Physik) of the
  Grassmannian Conference in Fundamental Cosmology (Grasscosmofun'09) Szczecin,
  Poland, 14-19 September 200
Some spaces are more equal than others

It has generally been thought that in perturbed
Friedmann-Lemaitre-Robertson-Walker models of the Universe, global topology
should not have any feedback effects on dynamics. However, a weak-field limit
heuristical argument, assuming a finite particle horizon for the transmission
of gravitational signals, shows that a residual acceleration effect can occur.
The nature of this effect differs algebraically between different constant
curvature 3-manifolds. This potentially provides a selection mechanism for the
3-manifold of comoving space.Comment: 4 pages, proceedings of the Grassmannian Conference in Fundamental
  Cosmology, Szczecin, 14-19 Sep 2009, to be refereed by Annalen der Physi
PPN limit and cosmological gravitational waves as tools to constrain
  f(R)-gravity

We discuss the PPN Solar-System constraints and the GW stochastic background
considering some recently proposed $f(R)$ gravity models which satisfy both
cosmological and stability conditions. Using the definition of PPN-parameters
$\gamma$ and $\beta$ in terms of $f(R)$-models and the definition of scalar
GWs, we compare and discuss if it is possible to search for parameter ranges of
$f(R)$-models working at Solar System and GW stochastic background scale.Comment: 4 pages, Grassmann Meeting 2009, Annalen der Physi
Galactic halos in cosmology with long-range scalar DM interaction

Based on a set of cosmological N-body simulations we analyze properties of
the dark matter haloes (DM) in a galaxy mass range ($10^{11} - 10^{13}
h^{-1}M_{\odot}$) in modified $\lcdm$ cosmology with additional dynamically
screened scalar interactions in DM sector. Our simulations show that scalar
interactions support picture of the Island Universe. Rapid structure formation
processes are shifted into higher redshifts resulting in a much smaller
accretion and merging rates for galactic haloes at low redshifts. Finally, we
present how this "fifth" force affects halo properties, like density profile,
triaxiality, ellipticities and the spin parameter.Comment: 4 pages, 2 figures, printed in Annalen Phys.19:351-354,2010,
  subsituted with the accepted versio
Noether symmetric minisuperspace model of $f(R)$ cosmology

We study the metric $f(R)$ cosmology using Noether symmetry approach by
utilizing the behavior of the corresponding Lagrangian under infinitesimal
generators of the desired symmetry. The existence of Noether symmetry of the
cosmological $f(R)$ minisuperspace helps us to find out the form of $f(R)$
function for which such symmetry exist. It is shown that the resulting form for
$f(R)$ yields a power law expansion for the cosmic scale factor. We also show
that in the corresponding Noether symmetric quantum model, the solutions to the
Wheeler-DeWitt equation can be expressed as a superposition of states of the
form $e^{iS}$. It is shown that in terms of such wavefunctions the classical
trajectories can be recovered.Comment: 5 pages, Talk given at "The Grassmannian Conference in Fundamental
  Cosmology (Grasscosmofun'09)", Szczecin, Poland, 14-19th September 200
Fundamental times, lengths and physical constants: some unknown
  contributions by Ettore Majorana

We review the introduction in physics of the concepts of an elementary space
length and of a fundamental time scale, analyzing some related unknown
contributions by Ettore Majorana. In particular, we discuss the
quasi-Coulombian scattering in presence of a finite length scale, as well as
the introduction of an intrinsic (universal) time delay in the expressions for
the retarded electromagnetic potentials. Finally, we also review a special
model considered by Majorana in order to deduce the value of the elementary
charge, in such a way anticipating key ideas later introduced in quantum
electrodynamics.Comment: 10 page
Functional renormalization group approach to the BCS-BEC crossover

The phase transition to superfluidity and the BCS-BEC crossover for an
ultracold gas of fermionic atoms is discussed within a functional
renormalization group approach. Non-perturbative flow equations, based on an
exact renormalization group equation, describe the scale dependence of the
flowing or average action. They interpolate continuously from the microphysics
at atomic or molecular distance scales to the macroscopic physics at much
larger length scales, as given by the interparticle distance, the correlation
length, or the size of the experimental probe. We discuss the phase diagram as
a function of the scattering length and the temperature and compute the gap,
the correlation length and the scattering length for molecules. Close to the
critical temperature, we find the expected universal behavior. Our approach
allows for a description of the few-body physics (scattering and molecular
binding) and the many-body physics within the same formalism.Comment: 30 pages, 13 figure
Necessity of Acceleration-Induced Nonlocality

The purpose of this paper is to explain clearly why nonlocality must be an
essential part of the theory of relativity. In the standard local version of
this theory, Lorentz invariance is extended to accelerated observers by
assuming that they are pointwise inertial. This locality postulate is exact
when dealing with phenomena involving classical point particles and rays of
radiation, but breaks down for electromagnetic fields, as field properties in
general cannot be measured instantaneously. The problem is corrected in
nonlocal relativity by supplementing the locality postulate with a certain
average over the past world line of the observer.Comment: 12 pages; v2: improved version accepted for publication in Ann. Phys.
  (Berlin
The Generalized SIC-OEP formalism and the Generalized SIC-Slater
  approximation (stationary and time-dependent cases)

We present a generalized formulation of the Optimized Effective Potential
(OEP) approach to the Self Interaction Correction (SIC) problem in Time
Dependent (TD) Density Functional Theory (DFT). The formulation relies on the
introduction of a double set of single electron orbitals. It allows the
derivation of a generalized Slater approximation to the full OEP formulation,
which extends the domain of validity of the standard Slater approximation. We
discuss both formal aspects and practical applications of the new formalism and
give illustrations in cluster and molecules. The new formalism provides a
valuable ansatz to more elaborate (and computationally very demanding) full TD
OEP and full TD SIC calculations especially in the linear domain
Energy and momentum of a spherically symmetric dilaton frame as
  regularized by teleparallel gravity

We calculate energy and momentum of a spherically symmetric dilaton frame
using the gravitational energy-momentum 3-form within the tetrad formulation of
general relativity (GR). The frame we use is characterized by an arbitrary
function $\Upsilon$ with the help of which all the previously found solutions
can be reproduced. We show how the effect of inertia {\it (which is mainly
reproduced from $\Upsilon$)} makes the total energy and momentum always
different from the well known result when we use the Riemannian connection
${{\widetilde \Gamma}_\alpha}^\beta$. On the other hand, when use is made of
the covariant formulation of teleparallel gravity, which implies to take into
account the pure gauge connection, teleparallel gravity always yields the
physically relevant result for the energy and momentum.Comment: 11 Pages Latex, Accepted for publication in Annalen der Physi
Anomalous criticality near semimetal-to-superfluid quantum phase
  transition in a two-dimensional Dirac cone model

We analyze the scaling behavior at and near a quantum critical point
separating a semimetallic from a superfluid phase. To this end we compute the
renormalization group flow for a model of attractively interacting electrons
with a linear dispersion around a single Dirac point. We study both ground
state and finite temperature properties. In two dimensions, the electrons and
the order parameter fluctuations exhibit power-law scaling with anomalous
scaling dimensions. The quasi-particle weight and the Fermi velocity vanish at
the quantum critical point. The order parameter correlation length turns out to
be infinite everywhere in the semimetallic ground state.Comment: 8 pages, 2 figures, typos correcte
High precision thermal modeling of complex systems with application to
  the flyby and Pioneer anomaly

Thermal modeling of complex systems faces the problems of an effective
digitalization of the detailed geometry and properties of the system,
calculation of the thermal flows and temperature maps, treatment of the thermal
radiation including possible multiple reflections, inclusion of additional
external influences, extraction of the radiation pressure from calculated
surface data, and computational effectiveness. In previous publications the
solution to these problems have been outlined and a first application to the
Pioneer spacecraft have been shown. Here we like to present the application of
our thermal modeling to the Rosetta flyby anomaly as well as to the Pioneer
anomaly. The analysis outlines that thermal recoil pressure is not the cause of
the Rosetta flyby anomaly but likely resolves the anomalous acceleration
observed for Pioneer 10.Comment: Accepted for publication in Ann. Phy
Next-to-next-to-leading order post-Newtonian spin-orbit Hamiltonian for
  self-gravitating binaries

We present the next-to-next-to-leading order post-Newtonian (PN) spin-orbit
Hamiltonian for two self-gravitating spinning compact objects. If at least one
of the objects is rapidly rotating, then the corresponding interaction is
comparable in strength to a 3.5PN effect. The result in the present paper in
fact completes the knowledge of the post-Newtonian Hamiltonian for binary
spinning black holes up to and including 3.5PN. The Hamiltonian is checked via
known results for the test-spin case and via the global Poincare algebra with
the center-of-mass vector uniquely determined by an ansatz.Comment: 9 pages, v2: revised version, v3: published version, v4: typo
  correcte