pinecone/core-2020-05-10-deduplication huggingface dataset:
Classical and fluctuation-induced electromagnetic interactions in
  micronscale systems: designer bonding, antibonding, and Casimir forces

Whether intentionally introduced to exert control over particles and
macroscopic objects, such as for trapping or cooling, or whether arising from
the quantum and thermal fluctuations of charges in otherwise neutral bodies,
leading to unwanted stiction between nearby mechanical parts, electromagnetic
interactions play a fundamental role in many naturally occurring processes and
technologies. In this review, we survey recent progress in the understanding
and experimental observation of optomechanical and quantum-fluctuation forces.
Although both of these effects arise from exchange of electromagnetic momentum,
their dramatically different origins, involving either real or virtual photons,
lead to different physical manifestations and design principles. Specifically,
we describe recent predictions and measurements of attractive and repulsive
optomechanical forces, based on the bonding and antibonding interactions of
evanescent waves, as well as predictions of modified and even repulsive Casimir
forces between nanostructured bodies. Finally, we discuss the potential impact
and interplay of these forces in emerging experimental regimes of
micromechanical devices.Comment: Review to appear on the topical issue "Quantum and Hybrid Mechanical
  Systems" in Annalen der Physi
Quantum capacitance and Landau parameters of massless Dirac fermions in
  graphene

We present extensive numerical results for the thermodynamic density of
states (i.e. quantum capacitance) of a two-dimensional massless Dirac fermion
fluid in a doped graphene sheet. In particular, by employing the random phase
approximation, we quantify the impact of screening exerted by a metal gate
located nearby a graphene flake. Finally, we calculate the spin- and
circularly-symmetric Landau parameter, which can be experimentally extracted
from independent measurements on the same setup of the quantum capacitance and
quasiparticle velocity.Comment: 7 pages, 5 figures, to be published in a Special Issue of Annalen der
  Physik on "Two-dimensional Materials: Electronic Structure and Many-Body
  Effects", edited by F. Guinea, M.I. Katsnelson, and T.O. Wehlin
Squeezing-enhanced measurement sensitivity in a cavity optomechanical
  system

We determine the theoretical limits to squeezing-enhanced measurement
sensitivity of mechanical motion in a cavity optomechanical system. The motion
of a mechanical resonator is transduced onto quadrature fluctuations of a
cavity optical field and a measurement is performed on the optical field
exiting the cavity. We compare measurement sensitivities obtained with coherent
probing and quantum-enhanced probing of the mechanical motion, i.e. the
coherent probe field carries vacuum states and quadrature squeezed vacuum
states at sideband frequencies, respectively. We find that quantum-enhanced
probing provides little to no improvement in motion sensing for resonators in
the unresolved sideband regime but may significantly increase measurement
sensitivities for resonators in the resolved sideband regime
Non-equilibrium dynamics in dissipative Bose-Hubbard chains

Open many-body quantum systems have recently gained renewed interest in the
context of quantum information science and quantum transport with biological
clusters and ultracold atomic gases. A series of results in diverse setups is
presented, based on a Master equation approach to describe the dissipative
dynamics of ultracold bosons in a one-dimensional lattice. The creation of
mesoscopic stable many-body structures in the lattice is predicted and the
non-equilibrium transport of neutral atoms in the regime of strong and weak
interactions is studied.Comment: invited paper to special issue of Annals of Physic
Relic photon temperature versus redshift and the cosmic neutrino
  background

Presuming that CMB photons are described by the deconfining phase of an SU(2)
Yang-Mills theory with the critical temperature for the
deconfining-preconfining phase transition matching the present CMB temperature
$T_0\sim 2.725\,$K (SU(2)$_{\tiny{CMB}}$), we investigate how CMB temperature
$T$ connects with the cosmological scale factor $a$ in a
Friedmann-Lema\^itre-Robertson-Walker Universe. Owing to a violation of
conformal scaling at late times, the tension between the (instantaneous)
redshift of reionisation from CMB observation ($z_{\tiny{re}}\sim 11$) and
quasar spectra ($z_{\tiny{re}}\sim 6$) is repealed. Also, we find that the
redshift of CMB decoupling moves from $z_{\tiny{dec}}\sim 1100$ to
$z_{\tiny{dec}}\sim 1775$ which questions $\Lambda$CDM cosmology at high
redshifts. Adapting this model to the conventional physics of three flavours of
massless cosmic neutrinos, we demonstrate inconsistency with the value
N$_{\tiny{eff}}\sim 3.36$ extracted from Planck data. Interactions between
cosmic neutrinos and the CMB implies a {\sl common} temperature $T$ of (no
longer separately conserved) CMB and neutrino fluids. N$_{\tiny{eff}}\sim 3.36$
then entails a universal, temperature induced cosmic neutrino mass $m_\nu=\xi
T$ with $\xi=3.973$. Our above results on $z_{\tiny{re}}$ and $z_{\tiny{dec}}$,
derived from SU(2)$_{\tiny{CMB}}$ alone, are essentially unaffected when
including such a neutrino sector.Comment: 19 pages, 5 figures, dedicated to the memory of Pierre van Baal and
  Dmitri Diakonov, v3: typos correcte
State complexity and quantum computation

The complexity of a quantum state may be closely related to the usefulness of
the state for quantum computation. We discuss this link using the tree size of
a multiqubit state, a complexity measure that has two noticeable (and, so far,
unique) features: it is in principle computable, and non-trivial lower bounds
can be obtained, hence identifying truly complex states. In this paper, we
first review the definition of tree size, together with known results on the
most complex three and four qubits states. Moving to the multiqubit case, we
revisit a mathematical theorem for proving a lower bound on tree size that
scales superpolynomially in the number of qubits. Next, states with
superpolynomial tree size, the Immanant states, the Deutsch-Jozsa states, the
Shor's states and the subgroup states, are described. We show that the
universal resource state for measurement based quantum computation, the
2D-cluster state, has superpolynomial tree size. Moreover, we show how the
complexity of subgroup states and the 2D cluster state can be verified
efficiently. The question of how tree size is related to the speed up achieved
in quantum computation is also addressed. We show that superpolynomial tree
size of the resource state is essential for measurement based quantum
computation. The necessary role of large tree size in the circuit model of
quantum computation is still a conjecture; and we prove a weaker version of the
conjecture.Comment: 15 pages, 9 figures. Annalen der Physik, Topical issue on Complex
  Quantum Systems, 201
Chaotic level mixing in a two-band Bose-Hubbard model

We present a two-band Bose-Hubbard model which is shown to be minimal in the
necessary coupling terms at resonant tunneling conditions. The dynamics of the
many-body problem is studied by sweeping the system across an avoided level
crossing. The linear sweep generalizes Landau-Zener transitions from
single-particle to many-body realizations. The temporal evolution of single-
and two-body observables along the sweeps is investigated in order to
characterize the non-equilibrium dynamics in our complex quantum system.Comment: invited paper for special issue of Annals of Physic
Nonlocal Effects in Black Body Radiation

Nonlocal electrodynamics is a formalism developed to include nonlocal effects
in the measurement process caused by the non-inertial state of the observers.
This theory modifies Maxwell's electrodynamics by eliminating the hypothesis of
locality that assumes an accelerated observer simultaneously equivalent to a
comoving inertial frame of reference. In this scenario, the transformation
between an inertial and accelerated observer is generalized which affects the
properties of physical fields. In particular, we analyze how an uniformly
accelerated observer perceives a homogeneous and isotropic blackbody radiation.
We show that all nonlocal effects are transient and most relevant in the first
period of acceleration.Comment: 10 pages, 5 figure
Supersymmetry after the Higgs

A brief review is given of the implications of a 126 GeV Higgs boson for the
discovery of supersymmetry. Thus a 126 GeV Higgs boson is problematic within
the Standard Model because of vacuum instability pointing to new physics beyond
the Standard Model. The problem of vacuum stability is overcome in the SUGRA
GUT model but the 126 GeV Higgs mass implies that the average SUSY scale lies
in the several TeV region. The largeness of the SUSY scale relieves the tension
on SUGRA models since it helps suppress flavor changing neutral currents and CP
violating effects and also helps in extending the proton life time arising from
baryon and lepton number violating dimension five operators. The geometry of
radiative breaking of the electroweak symmetry and fine tuning in view of the
large SUSY scale are analyzed.Consistency with the Brookhaven $g_{\mu}-2$
result is discussed. It is also shown that a large SUSY scale implied by the
126 GeV Higgs boson mass allows for light gauginos (gluino, charginos,
neutralinos) and sleptons. These along with the lighter third generation
squarks are the prime candidates for discovery at RUN II of the LHC.
Implication of the 126 GeV Higgs boson for the direct search for dark matter is
discussed. Also discussed are the sparticles mass hierarchies and their
relationship with the simplified models under the Higgs boson mass constraint.Comment: 10 pages, 10 figure
The Higgs boson, Supersymmetry and Dark Matter: Relations and
  Perspectives

The discovery of a light Higgs boson at the LHC opens a broad program of
studies and measurements to understand the role of this particle in connection
with New Physics and Cosmology. Supersymmetry is the best motivated and most
thoroughly formulated and investigated model of New Physics which predicts a
light Higgs boson and can explain dark matter. This paper discusses how the
study of the Higgs boson connects with the search for supersymmetry and for
dark matter at the LHC and at a future $e^+e^-$ collider and with dedicated
underground dark matter experiments.Comment: 7 pages, 5 figure
Matter-Antimatter Asymmetry - Aspects at Low Energy

The apparent dominance of matter over antimatter in our universe is an
obvious and puzzling fact which cannot be adequately explained in present
physical frameworks that assume matter-antimatter symmetry at the big bang.
However, our present knowledge of starting conditions and of known sources of
CP violation are both insufficient to explain the observed asymmetry. Therefore
ongoing research on matter-antimatter differences is strongly motivated as well
as attempts to identify viable new mechanisms that could create the present
asymmetry. Here we concentrate on possible precision experiments at low
energies towards a resolution of this puzzle.Comment: 6 pages, 1 figure; accepted for publication in Annalen der Physik
  (2015
Anderson transition for Google matrix eigenstates

We introduce a number of random matrix models describing the Google matrix G
of directed networks. The properties of their spectra and eigenstates are
analyzed by numerical matrix diagonalization. We show that for certain models
it is possible to have an algebraic decay of PageRank vector with the exponent
similar to real directed networks. At the same time the spectrum has no
spectral gap and a broad distribution of eigenvalues in the complex plain. The
eigenstates of G are characterized by the Anderson transition from localized to
delocalized states and a mobility edge curve in the complex plane of
eigenvalues.Comment: 9 pages, 12 figs, revte
Describing many-body bosonic waveguide scattering with the truncated
  Wigner method

We consider quasi-stationary scattering of interacting bosonic matter waves
in one-dimensional waveguides, as they arise in guided atom lasers. We show how
the truncated Wigner (tW) method, which corresponds to the semiclassical
description of the bosonic many-body system on the level of the diagonal
approximation, can be utilized in order to describe such many-body bosonic
scattering processes. Special emphasis is put on the discretization of space at
the exact quantum level, in order to properly implement the semiclassical
approximation and the tW method, as well as on the discussion of the results to
be obtained in the continuous limit.Comment: 9 pages, 3 figure
Refined comparison theorems for the Dirac equation in d dimensions

A single spin-$\frac{1}{2}$ particle obeys the Dirac equation in $d\ge 1$
spatial dimension and is bound by an attractive central monotone potential
which vanishes at infinity (in one dimension the potential is even). This work
refines the relativistic comparison theorems which were derived by Hall
\cite{p75}. The new theorems allow the graphs of the two comparison potentials
$V_a$ and $V_b$ to crossover in a controlled way and still imply the spectral
ordering $E_a\le E_b$ for the eigenvalues at the bottom of each angular
momentum subspace. More specifically in a simplest case we have: in dimension
$d=1$, if $\int_0^x (V_b(t)-V_a(t)) dt\ge 0,\ x\in [0,\ \infty)$, then $E_a\le
E_b$; and in $d>1$ dimensions, if $\int_0^r (V_b(t)-V_a(t))t^{2|k_d|} dt\ge 0,\
r\in [0,\ \infty)$, where $k_d=\tau\left(j+\frac{d-2}{2}\right)$ and $\tau=\pm
1$, then $E_a\le E_b$.Comment: 19 pages, 10 figure
Edge magnetotransport in graphene: A combined analytical and numerical
  study

The current flow along the boundary of graphene stripes in a perpendicular
magnetic field is studied theoretically by the nonequilibrium Green's function
method. In the case of specular reflections at the boundary, the Hall
resistance shows equidistant peaks, which are due to classical cyclotron
motion. When the strength of the magnetic field is increased, anomalous
resistance oscillations are observed, similar to those found in a
nonrelativistic 2D electron gas [New. J. Phys. 15:113047 (2013)]. Using a
simplified model, which allows to solve the Dirac equation analytically, the
oscillations are explained by the interference between the occupied edge states
causing beatings in the Hall resistance. A rule of thumb is given for the
experimental observability. Furthermore, the local current flow in graphene is
affected significantly by the boundary geometry. A finite edge current flows on
armchair edges, while the current on zigzag edges vanishes completely. The
quantum Hall staircase can be observed in the case of diffusive boundary
scattering. The number of spatially separated edge channels in the local
current equals the number of occupied Landau levels. The edge channels in the
local density of states are smeared out but can be made visible if only a
subset of the carbon atoms is taken into account.Comment: 13 pages, 12 figure
Cosmological implications of Higgs field fluctuations during inflation

Cosmological implications of Higgs field fluctuations during inflation are
considered. This study is based on the Standard Model and the standard
quadratic model of chaotic inflation where the Higgs field is minimally coupled
to gravity and has no direct coupling to the inflaton. In the Standard model
the renormalisation group improved effective potential develops an instability
(an additional minimum and maximum) at large field values. It is shown that
such a new maximum should take place at an energy scale above $10^{14}
\;\text{GeV},$ otherwise a universe like ours is extremely unlikely. The
extension to the case of the Higgs field interacting with the inflaton field is
discussed
Towards Quantum Cybernetics

Classical cybernetics is a successful meta-theory to model the regulation of
complex systems from an abstract information-theoretic viewpoint, regardless of
the properties of the system under scrutiny. Fundamental limits to the
controllability of an open system can be formalized in terms of the law of
requisite variety, which is derived from the second law of thermodynamics.
These concepts are briefly reviewed, and the chances, challenges and potential
gains arising from the generalisation of such a framework to the quantum domain
are discussed.Comment: Perspective article, close to published versio
Quantum efficiencies in finite disordered networks connected by
  many-body interactions

The quantum efficiency in the transfer of an initial excitation in disordered
finite networks, modeled by the $k$-body embedded Gaussian ensembles of random
matrices, is studied for bosons and fermions. The influence of the presence or
absence of time-reversal symmetry and centrosymmetry/centrohermiticity are
addressed. For bosons and fermions, the best efficiencies of the realizations
of the ensemble are dramatically enhanced when centrosymmetry
(centrohermiticity) is imposed. For few bosons distributed in two
single-particle levels this permits perfect state transfer for almost all
realizations when one-particle interactions are considered. For fermionic
systems the enhancement is found to be maximal for cases when all but one
single particle levels are occupied.Comment: 9 pages, 4 figures, submitted to Annalen der Physi
Capacitively coupled nano conductors: Ratchet currents and exchange
  fluctuation relations

We investigate electron transport in two quantum circuits with mutual Coulomb
interaction. The first circuit is a double quantum dot connected to two
electron reservoirs, while the second one is a quantum point contact in the
weak tunneling limit. The coupling is such that an electron in the first
circuit enhances the barrier of the point contact and, thus, reduces its
conductivity. While such setups are frequently used as charge monitors, we
focus on two different aspects. First, we derive transport coefficients which
have recently been employed for testing generalized equilibrium conditions
known as exchange fluctuation relations. These formally exact relations allows
us to test the consistency of our master equation approach. Second, a biased
point contact entails noise on the DQD and induces non-equilibrium phenomena
such as a ratchet current.Comment: 8 pages, 4 figure
Vibrational relaxation and decoherence in structured environments: a numerical investigation

Vibrational relaxation is a key issue in chemical reaction dynamics in condensed phase and at the gas-surface interface, where the environment is typically highly structured and cannot be expressed in terms of a simple friction coefficient. Rather, full knowledge of the coupling of the molecular oscillator to the environment is required, as typically subsumed in the spectral density of the environmental coupling. Here, we focus on harmonic Brownian motion and investigate the effectiveness of classical, canonical position autocorrelation functions to compute the spectral density of the coupling needed to describe vibrational relaxation in complex environments. Classical dynamics is performed on model systems, and several effects are investigated in detail, notably the presence of anharmonicity, the role of a high-frequency â��Debyeâ�� cutoff in the environment and the influence of the detailed structure of the latter. The spectral densities are then used in standard independent oscillator Hamiltonian models which are numerically solved at T = 0 K to investigate quantum relaxation and decoherenc
Boson Sampling as Canonical Transformation: A semiclassical approach in
  Fock space

We show that a theory of complex scattering between many-body (Fock) states
can be constructed such that its classical limit is a canonical transformation
thus encoding quantum interference in the semiclassical form of the associated
unitary operator. Based on this idea, we study the different coherent effects
expected under different choices of the many-body states and provide different
representations of the associated transition probabilities. In this way, we
derive exact relations and representations of the scattering process that can
be used to attack timely problems related with Boson Sampling.Comment: submitted to Ann. Phy
The matter-antimatter interpretation of Kerr spacetime

Repulsive gravity is not very popular in physics. However, one comes across
it in at least two main occurrences in general relativity: in the negative-$r$
region of Kerr spacetime, and as the result of the gravitational interaction
between matter and antimatter, when the latter is assumed to be CPT-transformed
matter. Here we show how these two independent developments of general
relativity are perfectly consistent in predicting gravitational repulsion and
how the above Kerr negative-$r$ region can be interpreted as the habitat of
antimatter. As a consequence, matter particles traveling along vortical
geodesics can pass through the throat of a rotating black hole and emerge as
antimatter particles (and vice versa). An experimental definitive answer on the
gravitational behavior of antimatter is awaited in the next few years.Comment: 8 pages, 1 figure. Reference [28] added. This is the pre-peer
  reviewed version of the article accepted for publication in Annalen der
  Physi
Dissipative Dynamics of Quantum Fluctuations

One way to look for complex behaviours in many-body quantum systems is to let
the number $N$ of degrees of freedom become large and focus upon collective
observables. Mean-field quantities scaling as $1/N$ tend to commute, whence
complexity at the quantum level can only be inherited from complexity at the
classical level. Instead, fluctuations of microscopic observables scale as
$1/\sqrt{N}$ and exhibit collective Bosonic features, typical of a mesoscopic
regime half-way between the quantum one at the microscopic level and the
classical one at the level of macroscopic averages. Here, we consider the
mesoscopic behaviour emerging from an infinite quantum spin chain undergoing a
microscopic dissipative, irreversible dynamics and from global states without
long-range correlations and invariant under lattice translations and dynamics.
We show that, from the fluctuations of one site spin observables whose linear
span is mapped into itself by the dynamics, there emerge bosonic operators
obeying a mesoscopic dissipative dynamics mapping Gaussian states into Gaussian
states. Instead of just depleting quantum correlations because of decoherence
effects, these maps can generate entanglement at the collective, mesoscopic
level, a phenomenon with no classical analogue that embodies a peculiar complex
behaviour at the interface between micro and macro regimes.Comment: LaTex, 30 page
Electromagnetic neutrinos in laboratory experiments and astrophysics

An overview of neutrino electromagnetic properties, which open a door to the
new physics beyond the Standard Model, is given. The effects of neutrino
electromagnetic interactions both in terrestrial experiments and in
astrophysical environments are discussed. The experimental bounds on neutrino
electromagnetic characteristics are summarized. Future astrophysical probes of
electromagnetic neutrinos are outlined.Comment: 18 pages, 2 figures, Revised version, Annalen der Physik [Ann. Phys.
  (Berlin)] in press. arXiv admin note: substantial text overlap with
  arXiv:1403.634