pinecone/core-2020-05-10-deduplication huggingface dataset:
Unconventional superconductivity and magnetism in Sr$_2$RuO$_4$ and
  related materials

We review the normal and superconducting state properties of the
unconventional triplet superconductor Sr$_2$RuO$_4$ with an emphasis on the
analysis of the magnetic susceptibility and the role played by strong
electronic correlations. In particular, we show that the magnetic activity
arises from the itinerant electrons in the Ru $d$-orbitals and a strong
magnetic anisotropy occurs ($\chi^{+-} < \chi^{zz}$) due to spin-orbit
coupling. The latter results mainly from different values of the $g$-factor for
the transverse and longitudinal components of the spin susceptibility (i.e. the
matrix elements differ). Most importantly, this anisotropy and the presence of
incommensurate antiferromagnetic and ferromagnetic fluctuations have strong
consequences for the symmetry of the superconducting order parameter. In
particular, reviewing spin fluctuation-induced Cooper-pairing scenario in
application to Sr$_2$RuO$_4$ we show how p-wave Cooper-pairing with line nodes
between neighboring RuO$_2$-planes may occur.
  We also discuss the open issues in Sr$_2$RuO$_4$ like the influence of
magnetic and non-magnetic impurities on the superconducting and normal state of
Sr$_2$RuO$_4$. It is clear that the physics of triplet superconductivity in
Sr$_2$RuO$_4$ is still far from being understood completely and remains to be
analyzed more in more detail. It is of interest to apply the theory also to
superconductivity in heavy-fermion systems exhibiting spin fluctuations.Comment: short review article. Annalen der Physik, vol. 13 (2004), to be
  publishe
Reduced density matrices, their spectral resolutions, and the
  Kimball-Overhauser approach

Recently, it has been shown, that the pair density of the homogeneous
electron gas can be parametrized in terms of 2-body wave functions (geminals),
which are scattering solutions of an effective 2-body Schr\"odinger equation.
For the corresponding scattering phase shifts, new sum rules are reported in
this paper. These sum rules describe not only the normalization of the pair
density (similar to the Friedel sum rule of solid state theory), but also the
contraction of the 2-body reduced density matrix. This allows one to calculate
also the momentum distribution, provided that the geminals are known from an
appropriate screening of the Coulomb repulsion. An analysis is presented
leading from the definitions and (contraction and spectral) properties of
reduced density matrices to the Kimball-Overhauser approach and its
generalizations. Thereby cumulants are used. Their size-extensivity is related
to the thermodynamic limit.Comment: 15 pages, conference contributio
Novel properties of wave propagation in biaxially anisotropic
  left-handed materials

Some physically interesting properties and effects of wave propagation in
biaxially anisotropic left-handed materials are investigated in this paper. We
show that in the biaxially gyrotropic left-handed material, the left-right
coupling of circularly polarized light arises due to the negative indices in
permittivity and permeability tensors of gyrotropic media. It is well known
that the geometric phases of photons inside a curved fiber in previous
experiments often depend on the cone angles of solid angles subtended by a
curve traced by the direction of wave vector of light, at the center of photon
momentum space. Here, however, for the light propagating inside certain
anisotropic left-handed media we will present a different geometric phase that
is independent of the cone angles. The extra phases of electromagnetic wave
resulting from the instantaneous helicity inversion at the interfaces between
left- and right- handed (LRH) media is also studied in detail by using the
Lewis-Riesenfeld invariant theory. Some interesting applications (e.g.,
controllable position-dependent frequency shift, detection of quantum-vacuum
geometric phases and helicity reversals at the LRH interfaces etc.) of above
effects and phenomena in left-handed media is briefly discussed.Comment: 18 pages, 0 figure, Late
On gravitational radiation and the energy flux of matter

A suitable derivative of Einstein's equations in the framework of the
teleparallel equivalent of general relativity (TEGR) yields a continuity
equation for the gravitational energy-momentum. In particular, the time
derivative of the total gravitational energy is given by the sum of the total
fluxes of gravitational and matter fields energy. We carry out a detailed
analysis of the continuity equation in the context of Bondi and Vaidya's
metrics. In the former space-time the flux of the gravitational energy is given
by the well known expression in terms of the square of the news function. It is
known that the energy definition in the realm of the TEGR yields the ADM
(Arnowitt-Deser-Misner) energy for appropriate boundary conditions. Here we
show that the same definition also describes the Bondi energy. The analysis of
the continuity equation in Vaidya's space-time shows that the variation of the
total gravitational energy is given by the energy flux of matter only.Comment: 22 pages, Latex file, no figures, to appear in the Annalen der Physi
The vanadium Magneli phases VnO(2n-1)

To compare the metal-insulator transitions (MITs) of VO2 and V2O3 we analyze
the relations between the structural and electronic properties of the vanadium
Magneli phases. These materials set up the homologous series VnO(2n-1) (3 <= n
<= 9) and have crystal structures comprising typical dioxide-like and
sesquioxide-like regions. As the MITs of the vanadium Magneli phases are
accompanied by structural transformations, we are able to discuss the effects
of characteristic changes in the local atomic environments. The systematic
investigation of the transport properties is based on a new and unifying
description of the crystal structures of the Magneli phases including VO2 and
V2O3. Our results lead to a comprehensive understanding of the MITs in the
Magneli class and shed new light on the role of particular electronic states
for the MIT of V2O3.Comment: 36 pages, 19 figures, more information at
  http://www.physik.uni-augsburg.de/theo2
Quantum Phase Diagram for Homogeneous Bose-Einstein Condensate

We calculate the quantum phase transition for a homogeneous Bose gas in the
plane of s-wave scattering length a_s and temperature T. This is done by
improving a one-loop result near the interaction-free Bose-Einstein critical
temperature T_c^{(0)} with the help of recent high-loop results on the shift of
the critical temperature due to a weak atomic repulsion using variational
perturbation theory. The quantum phase diagram shows a nose above T_c^{(0)}, so
that we predict the existence of a reentrant transition above T_c^{(0)}, where
an increasing repulsion leads to the formation of a condensate.Comment: Author Information under
  http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of
  paper (including all PS fonts) at
  http://www.physik.fu-berlin.de/~kleinert/34
Deep inside the pion. Reconciling QCD theory with data

Recent developments in the QCD description of the pion structure are
reviewed. The CLEO pion-photon transition data analysis favors a distribution
amplitude for the pion that is double-humped but endpoint-suppressed. After a
short outline of the derivation of this amplitude from QCD sum rules with
nonlocal condensates, we present the fully fledged analysis of the CLEO data
prefaced by predictions for the $F^{\gamma\rho\pi}$ form factor and commenting
on the inherent theoretical uncertainties due to higher twists and NNLO
perturbative corrections. We supplement our discussion by considering within
QCD factorization theory, the electromagnetic pion form factor at NLO accuracy
on one hand, and diffractive di-jets production on the other, comparing our
predictions with the respective experimental data from JLab and the Fermilab
E791 collaboration. In all cases, the agreement is impressive.Comment: 10 pages, 5 figures consisting of 8 eps files. Contribution to the
  Festschrift on the occasion of Klaus Goeke's 60th birthday, to appear in
  Annalen der Physi
Baryons as Fock states of 3,5,... quarks

We present a generating functional producing quark wave functions of all Fock
states in the octet, decuplet and antidecuplet baryons in the mean field
approximation, both in the rest and infinite momentum frames. In particular,
for the usual octet and decuplet baryons we get the SU(6)-symmetric wave
functions for their 3-quark component but with specific corrections from
relativism and from additional quark-antiquark pairs. For the exotic
antidecuplet baryons we obtain the 5-quark wave function.Comment: 20 p., 6 fig
3D parton imaging of the nucleon in high-energy pp and pA collisions

We discuss several examples of how the transverse spatial distribution of
partons in the nucleon, as well as multiparton correlations, can be probed by
observing hard processes (dijets) in high-energy pp (pbar p) and pA (dA)
collisions. Such studies can complement the information gained from
measurements of hard exclusive processes in ep scattering. The transverse
spatial distribution of partons determines the distribution over pp impact
parameters of events with hard dijet production. Correlations in the transverse
positions of partons can be studied in multiple dijet production. We find that
the correlation cross section measured by the CDF Collaboration, sigma_eff =
14.5 +/- 1.7^{+ 1.7}_{-2.3} mb, can be explained by "constituent quark" type
quark-gluon correlations with r_q ~ r_N / 3, as suggested by the instanton
liquid model of the QCD vacuum. Longitudinal and transverse multiparton
correlations can be separated in a model-independent way by comparing multiple
dijet production in pp and pA collisions. Finally, we estimate the cross
section for exclusive diffractive Higgs production in pp collisions at LHC
(rapidity gap survival probability), by combining the impact parameter
distribution implied by the hard partonic process with information about soft
interactions gained in pp elastic scattering.Comment: 9 pages, 3 figures. To appear in the Festschrift on the occasion of
  Klaus Goeke's 60th birthda
Some comments on the handbag approach to wide-angle exclusive scattering

The handbag mechanism for wide-angle exclusive scattering reactions is
discussed and compared to other theoretical approaches. The role of power laws
in observables is critically examined. Applications of the handbag mechanism to
Compton scattering and meson photoproduction are presented. The soft physics
input to these processes are specific form factors which represent 1/x moments
of generalized parton distributions at zero skewness. A recent analysis of the
nucleon form factors provide these GPDs and, hence, the new form factors.Comment: 10 pages, 7 figures, contribution to Festschrift for Klaus Goeke's
  60th birthday, to be published in Annalen der Physi
Recent progress in the understanding of single spin asymmetries

Over the past years a lot of progress has been made in the understanding of
single spin asymmetries in hard scattering processes. We briefly review this
subject, covering the non-vanishing of time-reversal odd parton distributions,
universality of fragmentation functions, and the discovery of previously
unknown time-reversal odd parton distributions at subleading twist.
Interestingly enough, all these developments were initiated by simple model
calculations.Comment: 10 pages, contribution to the Festschrift on the occasion of Klaus
  Goeke's 60th birthday; references adde
SU(3) constraints on cryptoexotic pentaquarks

We examine SU(3) constraints on the spectrum and decay widths of cryptoexotic
nucleon-like states in antidecuplet of pentaquarks. We show that in the ideal
mixing scenario the number of free matrix elements describing splittings
reduces from 4 to 2. Model-independent sum rules are derived.
  Using as input $\Theta^+$ and $\Xi_{3/2}$ masses we show that it is difficult
to interpret Roper and $N^{\ast}(1710)$ nucleon resonances as cryptoexotic
pentaquarks. Large $N_c$ limit for antidecuplet and accompanying octet in the
diqaurk picture and the analogy with the soliton model is also discussed.Comment: 9 pages, 5 figures, contribution to Festschrift for Klaus Goeke's
  60th birthday, to be published in Nov./Dec. 2004 issue of Annalen der Physi
QCD Sum Rules and Models for Generalized Parton Distributions

I use QCD sum rule ideas to construct models for generalized parton
distributions. To this end, the perturbative parts of QCD sum rules for the
pion and nucleon electromagnetic form factors are interpreted in terms of GPDs
and two models are discussed. One of them takes the double Borel transform at
adjusted value of the Borel parameter as a model for nonforward parton
densities, and another is based on the local duality relation. Possible ways of
improving these Ans{\"a}tze are briefly discussed.Comment: Contribution to the Festschrift on the occasion of Klaus Goeke's 60th
  birthday, to appear in Annalen der Physi
Quadratic metric-affine gravity

We consider spacetime to be a connected real 4-manifold equipped with a
Lorentzian metric and an affine connection. The 10 independent components of
the (symmetric) metric tensor and the 64 connection coefficients are the
unknowns of our theory. We introduce an action which is quadratic in curvature
and study the resulting system of Euler-Lagrange equations. In the first part
of the paper we look for Riemannian solutions, i.e. solutions whose connection
is Levi-Civita. We find two classes of Riemannian solutions: 1) Einstein
spaces, and 2) spacetimes with metric of a pp-wave and parallel Ricci
curvature. We prove that for a generic quadratic action these are the only
Riemannian solutions. In the second part of the paper we look for
non-Riemannian solutions. We define the notion of a "Weyl pseudoinstanton"
(metric compatible spacetime whose curvature is purely Weyl) and prove that a
Weyl pseudoinstanton is a solution of our field equations. Using the
pseudoinstanton approach we construct explicitly a non-Riemannian solution
which is a wave of torsion in Minkowski space. We discuss the possibility of
using this non-Riemannian solution as a mathematical model for the graviton or
the neutrino.Comment: 25 pages, LaTeX2
On the interaction of mesoscopic quantum systems with gravity

We review the different aspects of the interaction of mesoscopic quantum
systems with gravitational fields. We first discuss briefly the foundations of
general relativity and quantum mechanics. Then, we consider the
non-relativistic expansions of the Klein-Gordon and Dirac equations in the
post-Newtonian approximation. After a short overview of classical gravitational
waves, we discuss two proposed interaction mechanisms: (i) the use of quantum
fluids as generator and/or detector of gravitational waves in the laboratory,
and (ii) the inclusion of gravitomagnetic fields in the study of the properties
of rotating superconductors. The foundations of the proposed experiments are
explained and evaluated.Comment: 27 pages, study for ESA: typos corrected, references and
  clarifications added. To appear in Annalen der Physi
From Einstein's 1905 Postulates to the Geometry of Flat Space-Time

Minkowski diagrams in 1+1 dimensional flat space-time are given a strictly
geometric derivation, directly from two gedanken experiments incorporating the
principle of the constancy of the velocity of light and the principle of
(special) relativity. Rectangles of photon trajectories play a central role in
determining the simultaneity convention and in establishing the invariance of
the interval.Comment: A few typos and some obvious misstatements have been repaired. A
  reference has been added. 18 pages, 12 figures. To appear in Annalen der
  Physik (Leipzig) 14 (2005) [1-3], Special Topic Issue. Albert Einstein: His
  Work and His Impac
Cosmological constant and vacuum energy

The general thermodynamic analysis of the quantum vacuum, which is based on
our knowledge of the vacua in condensed-matter systems, is consistent with the
Einstein earlier view on the cosmological constant. In the equilibrium
Universes the value of the cosmological constant is regulated by matter. In the
empty Universe, the vacuum energy is exactly zero, lambda=0. The huge
contribution of the zero point motion of the quantum fields to the vacuum
energy is exactly cancelled by the higher-energy degrees of freedom of the
quantum vacuum. In the equilibrium Universes homogeneously filled by matter,
the vacuum is disturbed, and density of the vacuum energy becomes proportional
to the energy density of matter. This consideration applies to any equilibrium
vacuum irrespective of whether the vacuum is false or true, and is valid both
in the Einstein general theory of relativity and within the special theory of
relativity, i.e. in the world without gravity.Comment: 23 pages, accepted for special topic issue of Annalen der Physik
  related to Einstein's contributions to physics, references and figure adde
Tidal Dynamics of Relativistic Flows Near Black Holes

DOI: 	10.1002/andp.200410126                 http://arxiv.org/PS_cache/astro-ph/pdf/0404/0404170v3.pdfWe point out novel consequences of general relativity involving tidal dynamics of ultrarelativistic relative motion. Specifically, we use the generalized Jacobi equation and its extension to study the force-free dynamics of relativistic flows near a massive rotating source. We show that along the rotation axis of the gravitational source, relativistic tidal effects strongly decelerate an initially ultrarelativistic flow with respect to the ambient medium, contrary to Newtonian expectations. Moreover, an initially ultrarelativistic flow perpendicular to the axis of rotation is strongly accelerated by the relativistic tidal forces. The astrophysical implications of these results for jets and ultrahigh energy cosmic rays are briefly mentioned
Brownian motion: a paradigm of soft matter and biological physics

This is a pedagogical introduction to Brownian motion on the occasion of the
100th anniversary of Einstein's 1905 paper on the subject. After briefly
reviewing Einstein's work in its contemporary context, we pursue some lines of
further developments and applications in soft condensed matter and biology.
Over the last century Brownian motion became promoted from an odd curiosity of
marginal scientific interest to a guiding theme pervading all of the modern
(live) sciences.Comment: 30 pages, revie
Derivation of Poincare Invariance from general quantum field theory

Starting from a very general quantum field theory we seek to derive Poincare
invariance in the limit of low energy excitations. We do not, of course, assume
these symmetries at the outset, but rather only a very general second quantised
model. Many of the degrees of freedom on which the fields depend turn out to
correspond to a higher dimension. We are not yet perfectly successful. In
particular, for the derivation of translational invariance, we need to assume
that some background parameters, which a priori vary in space, can be
interpreted as gravitational fields in a future extension of our model.
Assuming translational invariance arises in this way, we essentially obtain
quantum electrodynamics in just 3 + 1 dimensions from our model. The only
remaining flaw in the model is that the photon and the various Weyl fermions
turn out to have their own separate metric tensors.Comment: 35 pages, to be published in Annalen der Physik, Special Issue
  commemorating Albert Einstei
Darboux transformation for two-level systems

We develop the Darboux procedure for the case of the two-level system. In
particular, it is demonstrated that one can construct the Darboux intertwining
operator that does not violate the specific structure of the equations of the
two-level system, transforming only one real potential into another real
potential. We apply the obtained Darboux transformation to known exact
solutions of the two-level system. Thus, we find three classes of new solutions
for the two-level system and the corresponding new potentials that allow such
solutions.Comment: 10 page
Modeling Na clusters in Ar matrices

We present a microscopic model for Na clusters embedded in raregas matrices.
The valence electrons of the Na cluster are described by time-dependent
density-functional theory at the level of the local-density approximation
(LDA). Particular attention is paid to the semi-classical picture in terms of
Vlasov-LDA. The Na ions and Argon atoms are handled as classical particles
whereby the Ar atoms carry two degrees of freedom, position and dipole
polarization. The interaction between Na ions and electrons is mediated through
local pseudo-potentials. The coupling to the Ar atoms is described by
(long-range) polarization potentials and (short-range) repulsive cores. The
ingredients are taken from elsewhere developed standards. A final fine-tuning
is performed using the NaAr molecule as benchmark. The model is then applied to
embedded systems Na8ArN. By close comparison with quantum-mechanical results,
we explore the capability of the Vlasov-LDA to describe such embedded clusters.
We show that one can obtain a reasonable description by appropriate adjustments
in the fine-tuning phase of the model.Comment: 17 pages, 7 figures, submitted to Annalen der Physi
Spontaneous emission of light from atoms: the model

We investigate (non-relativistic) atomic systems interacting with quantum
electromagnetic field (QEF). The resulting model describes spontaneous emission
of light from a two-level atom surrounded by various initial states of the QEF.
We assume, that the quantum field interacts with the atom via the standard,
minimal-coupling Hamiltonian, with the $A^2$ term neglected. We also assume,
that there will appear at most single excitations (photons). By conducting the
analysis on a general level we allow for an arbitrary initial state of the QEF
(which can be for instance: the vacuum, the ground state in a cavity, or the
squeezed state). We derive a Volterra-type equation which governs the time
evolution of the amplitude of the excited state. The two-point function of the
initial state of the QEF, integrated with a combination of atomic
wavefunctions, forms the kernel of this equation.Comment: (improved version, minor mistakes removed, accepted by Annalen der
  Physik
Semiclassical Quantum Gravity: Statistics of Combinatorial Riemannian
  Geometries

This paper is a contribution to the development of a framework, to be used in
the context of semiclassical canonical quantum gravity, in which to frame
questions about the correspondence between discrete spacetime structures at
"quantum scales" and continuum, classical geometries at large scales. Such a
correspondence can be meaningfully established when one has a "semiclassical"
state in the underlying quantum gravity theory, and the uncertainties in the
correspondence arise both from quantum fluctuations in this state and from the
kinematical procedure of matching a smooth geometry to a discrete one. We focus
on the latter type of uncertainty, and suggest the use of statistical geometry
as a way to quantify it. With a cell complex as an example of discrete
structure, we discuss how to construct quantities that define a smooth
geometry, and how to estimate the associated uncertainties. We also comment
briefly on how to combine our results with uncertainties in the underlying
quantum state, and on their use when considering phenomenological aspects of
quantum gravity.Comment: 26 pages, 2 figure