pinecone/core-2020-05-10-deduplication huggingface dataset:
All-optical photonic band control in a quantum metamaterial

Metamaterials made of periodic collections of dielectric nanorods are
considered theoretically. When quantum resonators are embedded within the
nanorods, one obtains a quantum metamaterial, whose electromagnetic properties
depend upon the state of the quantum resonators. The theoretical model predicts
that when the resonators are pumped and reach the inversion regime, the quantum
metamaterial exhibits an all-optical switchable conduction band. The phenomenon
can be described by considering the pole stucture of the scattering matrix of
the metamaterial.Comment: submitted to Annalen der Physik, special issue on "Quantum dynamics
  at the extreme
The gravitational energy-momentum pseudo-tensor of Higher-Order Theories
  of Gravity

We derive the gravitational energy momentum tensor $\tau^{\eta}_{\alpha}$ for
a general Lagrangian of any order $L=L\left(g_{\mu\nu}, g_{\mu\nu,i_{1}},
g_{\mu\nu,i_{1}i_{2}},g_{\mu\nu,i_{1}i_{2}i_{3}},\cdots,
g_{\mu\nu,i_{1}i_{2}i_{3}\cdots i_{n}}\right)$ and in particular for a
Lagrangian such as $L_{g}=(\overline{R}+a_{0}R^{2}+\sum_{k=1}^{p}
a_{k}R\Box^{k}R)\sqrt{-g}$. We prove that this tensor, in general, is not
covariant but only affine, then it is a pseudo-tensor. Furthermore, the
pseudo-tensor $\tau^{\eta}_{\alpha}$ is calculated in the weak field limit up
to a first non-vanishing term of order $h^{2}$ where $h$ is the metric
perturbation. The average value of the pseudo-tensor over a suitable spacetime
domain is obtained. Finally we calculate the power per unit solid angle
$\Omega$ carried by a gravitational wave in a direction $\hat{x}$ for a fixed
wave number $\mathbf{k}$ under a suitable gauge. These results are useful in
view of searching for further modes of gravitational radiation beyond the
standard two modes of General Relativity and to deal with nonlocal theories of
gravity where terms involving $\Box R$ are present. The general aim of the
approach is to deal with theories of any order under the same standard of
Landau pseudo-tensor.Comment: 23 pages, to be published in Annalen der Physi
Classical and quantum systems: transport due to rare events

We review possible mechanisms for energy transfer based on 'rare' or
'non-perturbative' effects, in physical systems that present a many-body
localized phenomenology. The main focus is on classical systems, with or
without quenched disorder. For non-quantum systems, the breakdown of
localization is usually not regarded as an issue, and we thus aim at
identifying the fastest channels for transport. Next, we contemplate the
possibility of applying the same mechanisms in quantum systems, including
disorder free systems (e.g. Bose-Hubbard chain), disordered many-body localized
systems with mobility edges at energies below the edge, and strongly disordered
lattice systems in $d>1$. For quantum mechanical systems, the relevance of
these considerations for transport is currently a matter of debate.Comment: Review paper. To appear on the special issue on Many-body
  Localization in Annalen der Physi
Quantum transport in the black-hole configuration of an atom condensate
  outcoupled through an optical lattice

The outcoupling of a Bose-Einstein condensate through an optical lattice
provides an interesting scenario to study quantum transport phenomena or the
analog Hawking effect as the system can reach a quasi-stationary black-hole
configuration. We devote this work to characterize the quantum transport
properties of quasi-particles on top of this black-hole configuration by
computing the corresponding scattering matrix. We find that most of the
features can be understood in terms of the usual Schr\"odinger scattering. In
particular, a transmission band appears in the spectrum, with the normal-normal
transmission dominating over the anomalous-normal one. We show that this
picture still holds in a realistic experimental situation where the actual
Gaussian envelope of the optical lattice is considered. A peaked resonant
structure is displayed near the upper end of the transmission band, which
suggests that the proposed setup is a good candidate to provide a clear signal
of spontaneous Hawking radiation.Comment: 27 pages, 8 figure
London penetration depth and thermal fluctuations in the sulphur hydride
  203 K superconductor

Recently, compressed H$_2$S has been shown to become superconducting at 203 K
under a pressure of 155 GPa. One might expect fluctuations to dominate at such
temperatures. Using the magnetisation critical current, we determine the
ground-state London penetration depth, $\lambda_0$=189 nm, and the
superconducting energy gap, $\Delta_0$=27.8 meV, and find these parameters are
similar to those of cuprate superconductors. We also determine the fluctuation
temperature scale, $T_{\textrm{fluc}}=1470$ K, which shows that, unlike the
cuprates, $T_c$ of the hydride is not limited by fluctuations. This is due to
its three dimensionality and suggests the search for better superconductors
should refocus on three-dimensional systems where the inevitable thermal
fluctuations are less likely to reduce the observed $T_c$.Comment: 10 pages, 1 Figure. Annalen der Physik, published online 23 December
  2016, http://onlinelibrary.wiley.com/doi/10.1002/andp.201600390/abstrac
Many-body localization in incommensurate models with a mobility edge

We review the physics of many-body localization in models with incommensurate
potentials. In particular, we consider one-dimensional quasiperiodic models
with single-particle mobility edges. Although a conventional perspective
suggests that delocalized states act as a thermalizing bath for the localized
states in the presence of of interactions, there is evidence that such systems
can display non-ergodicity. This is in part due to the fact that the
delocalized states do not have any kind of protection due to symmetry or
topology and are thus susceptible to localization. A study of non-interacting
incommensurate models shows that they admit extended, partially extended, and
fully localized many-body states. These models cannot thermalize dynamically
and remain localized upon the introduction of interactions. In particular, for
a certain range of energy, the system can host a non-ergodic extended (i.e.
metallic) phase in which the energy eigenstates violate the eigenstate
thermalization hypothesis (ETH) but the entanglement entropy obeys volume-law
scaling. The level statistics and entanglement growth also indicate the lack of
ergodicity in these models. The phenomenon of localization and non-ergodicity
in a system with interactions despite the presence of single-particle
delocalized states is closely related to the so-called "many-body proximity
effect" and can also be observed in models with disorder coupled to systems
with delocalized degrees of freedom. Many-body localization in systems with
incommensurate potentials (without single-particle mobility edges) have been
realized experimentally, and we show how this can be modified to study the the
effects of such mobility edges. Demonstrating the failure of thermalization in
the presence of a single-particle mobility edge in the thermodynamic limit
would indicate a more robust violation of the ETH.Comment: 17 pages, 14 figures, Review articl
Quantum bifurcation diagrams

Asymptotic state of an open quantum system can undergo qualitative changes
upon small variation of system parameters. We demonstrate it that such 'quantum
bifurcations' can be appropriately defined and made visible as changes in the
structure of the asymptotic density matrix. By using an $N$-boson open quantum
dimer, we present quantum diagrams for the pitchfork and saddle-node
bifurcations in the stationary case and visualize a period-doubling transition
to chaos for the periodically modulated dimer. In the latter case, we also
identify a specific bifurcation of purely quantum nature.Comment: 6 pages, 4 figure
Terahertz electric field driven electric currents and ratchet effects in
  graphene

Terahertz field induced photocurrents in graphene were studied experimentally
and by microscopic modeling. Currents were generated by cw and pulsed laser
radiation in large area as well as small-size exfoliated graphene samples. We
review general symmetry considerations leading to photocurrents depending on
linear and circular polarized radiation and then present a number of situations
where photocurrents were detected. Starting with the photon drag effect under
oblique incidence, we proceed to the photogalvanic effect enhancement in the
reststrahlen band of SiC and edge-generated currents in graphene. Ratchet
effects were considered for in-plane magnetic fields and a structure inversion
asymmetry as well as ratchets by non-symmetric patterned top gates. Lastly, we
demonstrate that graphene can be used as a fast, broadband detector of
terahertz radiation
High intensity generation of entangled photons in a two-mode
  electromagnetic field

At present, the sources of entangled photons have a low rate of photon
generation. This limitation is a key component of quantum informatics for the
realization of such functions as linear quantum computation and quantum
teleportation. In this paper, we propose a method for high intensity generation
of entangled photons in a two-mode electromagnetic field. On the basis of exact
solutions of the Schr{\"o}dinger equation, in the conditions of interaction of
the electrons in an atom with a strong two-mode electromagnetic field, it is
shown that there may be large quantum entanglement between photons. The quantum
entanglement is analyzed on the basis of the Schmidt parameter. It is shown
that the Schmidt parameter can reach very high values depending on the choice
of characteristics of the two-mode fields. We find the Wigner function for the
considered case. Violation of Bell's inequalities for continuous variables is
demonstrated
Modelling spatial variations of the speed of light

In this paper we extend a new method to measure possible variation of the
speed of light by using Baryon Acoustic Oscillations and the Hubble function
presented in our earlier paper [V. Salzano, M. P. D\c{a}browski, and R. Lazkoz,
Phys. Rev. D93, 063521 (2016)] onto an inhomogeneous model of the universe. The
method relies on the fact that there is a simple relation between the angular
diameter distance $(D_{A})$ maximum and the Hubble function $(H)$ evaluated at
the same maximum-condition redshift, which includes speed of light $c$. One
limit of such method was the assumption of null spatial curvature (even if we
showed that even a non-zero curvature would have negligible effects). Here, we
move one step further: we explicitly assume a model with intrinsic non-null
curvature, and calculate the exact relation between $D_{A}$ and $H$ in this
case. Then, we evaluate if current or future missions such as SKA can be
sensitive enough to detect any such kind of spatial variation of $c$ which can
perhaps be related to the recently observed spatial variation of the fine
structure constant (an effect known as $\alpha$-dipole).Comment: 7 pages, 1 tabl
The final state of gravitational collapse in Eddington-inspired
  Born-Infeld theory

In this paper, we address the implications when a homogeneous dust model is
considered for a scenario of gravitational collapse in the context of
Eddington-inspired Born-Infeld (EiBI) theory. In order to describe the
dynamical evolution of the collapse, we present an effective equation, which
constitutes the first order corrections, in EiBI coupling parameter $\kappa$,
to Einstein's field equations. The geometry outside the collapsing object is
derived by imposing the standard Darmois-Israel junction conditions at the
boundary surface of the dust. This induces an effective matter source in the
outer region which gives rise to a non-singular, non-Schwarzschild geometry at
the final state of the collapse. For this exterior geometry, we find the
threshold of mass for the formation of the black hole. This provides a cut-off
over $\kappa$ as $|\kappa|=5.1\times10^{-97} ~kg^{-1}\cdot m^3$.Comment: 10 pages, 3 figures, Version accepted in Annalen der Physi
Invariant-based pulse design for three-level systems without the
  rotating-wave approximation

In this paper, a scheme is put forward to design pulses which drive a
three-level system based on the reverse engineering with Lewis-Riesenfeld
invariant theory. The scheme can be applied to a three-level system even when
the rotating-wave approximation (RWA) can not be used. The amplitudes of pulses
and the maximal values of detunings in the system could be easily controlled by
adjusting control parameters. We analyze the dynamics of the system by an
invariant operator, so additional couplings are unnecessary. Moreover, the
approaches to avoid singularity of pulses are studied and several useful
results are obtained. We hope the scheme could contribute to fast quantum
information processing without RWA.Comment: 9 pages 9 figures, has been accepted for publication as a Regular
  Article in Annalen der Physi
Quantum Emulation of Extreme Non-equilibrium Phenomena with Trapped
  Atoms

Ultracold atomic physics experiments offer a nearly ideal context for the
investigation of quantum systems far from equilibrium. We describe three
related emerging directions of research into extreme non-equilibrium phenomena
in atom traps: quantum emulation of ultrafast atom-light interactions, coherent
phasonic spectroscopy in tunable quasicrystals, and realization of Floquet
matter in strongly-driven lattice systems. We show that all three should enable
quantum emulation in parameter regimes inaccessible in solid-state experiments,
facilitating a complementary approach to open problems in non-equilibrium
condensed matter.Comment: 12 pages, 7 figure
Ultra-fast control of magnetic relaxation in a periodically driven
  Hubbard model

Motivated by cold atom and ultra-fast pump-probe experiments we study the
melting of long-range antiferromagnetic order of a perfect N\'eel state in a
periodically driven repulsive Hubbard model. The dynamics is calculated for a
Bethe lattice in infinite dimensions with non-equilibrium dynamical mean-field
theory. In the absence of driving melting proceeds differently depending on the
quench of the interactions to hopping ratio $U/J_0$ from the atomic limit. For
$U \gg J_0$ decay occurs due to mobile charge-excitations transferring energy
to the spin sector, while for $J_0 \gtrsim U$ it is governed by the dynamics of
residual quasi-particles. Here we explore the rich effects strong periodic
driving has on this relaxation process spanning three frequency $\omega$
regimes: (i) high-frequency $\omega \gg U,J_0$, (ii) resonant $l\omega = U >
J_0$ with integer $l$, and (iii) in-gap $U > \omega > J_0$ away from resonance.
In case (i) we can quickly switch the decay from quasi-particle to
charge-excitation mechanism through the suppression of $J_0$. For (ii) the
interaction can be engineered, even allowing an effective $U=0$ regime to be
reached, giving the reverse switch from a charge-excitation to quasi-particle
decay mechanism. For (iii) the exchange interaction can be controlled with
little effect on the decay. By combining these regimes we show how periodic
driving could be a potential pathway for controlling magnetism in
antiferromagnetic materials. Finally, our numerical results demonstrate the
accuracy and applicability of matrix product state techniques to the
Hamiltonian DMFT impurity problem subjected to strong periodic driving
Quantum transition between magnetically ordered and Mott glass phases

We discuss a quantum transition from a superfluid to a Mott glass phases in
disordered Bose-systems by the example of an isotropic spin-$\frac12$
antiferromagnet with spatial dimension $d\ge2$ and with disorder in tunable
exchange couplings. Our analytical consideration is based on general properties
of a system in critical regime, on the assumption that the magnetically order
part of the system shows fractal properties near the transition, and on a
hydrodynamic description of long-wavelength magnons in the magnetically ordered
("superfluide") phase. Our results are fully consistent with a scaling theory
based on an ansatz for the free energy proposed by M.P. Fisher et al. (Phys.
Rev. B 40, 546 (1989)). We obtain $z=d-\beta/\nu$ for the dynamical critical
exponent and $\phi = z\nu$, where $\phi$, $\beta$, and $\nu$ are critical
exponents of the critical temperature, the order parameter, and the correlation
length, respectively. The density of states of localized excitations (fractons)
is found to show a superuniversal (i.e., independent of $d$) behavior.Comment: 8 pages, 2 figures, a few slight rectifications. arXiv admin note:
  text overlap with arXiv:1604.0872
Role of the radiation-reaction electric field in the optical response of
  two-dimensional crystals

A classical theory of a radiating two-dimensional crystal is proposed and an
expression for the radiative-reaction electric field is derived. This field
plays an essential role in connecting the microscopic electromagnetic fields
acting on each dipole of the crystal to the macroscopic one, via the boundary
conditions for the system. The expression of the radiative-reaction electric
field coincides with the macroscopic electric field radiating from the crystal
and, summed to the incident electric field, generates the total macroscopic
electric field.Comment: Two-dimensional crystal, metasurface, local field,
  radiative-reaction, Fresnel, boundary conditio
Nonlinear electrodynamics and magnetic black holes

A model of nonlinear electrodynamics with two parameters, coupled with
general relativity, is investigated. We study the magnetized black hole and
obtain solutions. The asymptotic of the metric and mass functions at
$r\rightarrow\infty$ and $r\rightarrow 0$, and corrections to the
Reissner-Nordstr\"{o}m solution are found. We investigate thermodynamics of
black holes and calculate the Hawking temperature and heat capacity of black
holes. It is shown that there are phase transitions and at some parameters of
the model black holes are stable.Comment: 14 pages, 6 figures, 2 table
Quantum kinetic theory of a massless scalar model in the presence of a
  Schwarzschild black hole

We employ quantum kinetic theory to investigate local quantum physics in the
background of spherically symmetric and neutral black holes formed through the
gravitational collapse. For this purpose in mind, we derive and study the
covariant Wigner distribution function $\mathcal{W}(x,p)$ near to and far away
from the black-hole horizon. We find that the local density of the particle
number is negative in the near-horizon region, while the entropy density is
imaginary. These pose a question whether kinetic theory is applicable in the
near-horizon region. We elaborate on that and propose a possible interpretation
of how this result might nevertheless be self-consistently understood.Comment: version to be published in Annalen der Physi
Spectral classification of one-dimensional binary aperiodic crystals: an algebraic approach

A spectral classification of general one-dimensional binary aperiodic crystals (BACs) based on both their diffraction patterns and energy spectrum measures is introduced along with a systematic comparison of the zeroth-order energy spectrum main features for BACs belonging to different spectral classes, including Fibonacci-class, precious means, metallic means, mixed means and period doubling based representatives. These systems are described by means of mixed-type Hamiltonians which include both diagonal and off-diagonal terms aperiodically distributed. An algebraic approach highlighting chemical correlation effects present in the underlying lattice is introduced. Close analytical expressions are obtained by exploiting some algebraic properties of suitable blocking schemes preserving the atomic order of the original lattice. The existence of a resonance energy which defines the basic anatomy of the zeroth-order energy spectra structure for the standard Fibonacci, the precious means and the Fibonacci-class quasicrystals is disclosed. This eigenstate is also found in the energy spectra of BACs belonging to other spectral classes, but for specific particular choices of the corresponding model parameters only. The transmission coefficient of these resonant states is always bounded below, although their related Landauer conductance values may range from highly conductive to highly resistive ones, depending on the relative strength of the chemical bonds
TeV- and MeV-physics out of an $SU_{L}(2)\times U_{R}(1)_{J} \times
  U(1)_{K}$ model

The standard electroweak interaction is here re-assessed to accommodate two
different situations in Particle Physics. The first one is a $Z'$-model at the
TeV-scale physics. The second one tackles the recent discussion of a possible
fifth force mediated by a $17$-MeV X-boson associated with an electron-positron
emission in the transition of an excited 8-Beryllium to its ground state. The
anomaly-free model that provides these two scenarios is based on an $SU_{L}(2)
\times U_{R}(1)_{J} \times U(1)_{K}$-symmetry. It yields a new massive neutral
boson, an exotic massive neutral fermion, right-neutrinos and an additional
neutral Higgs particle, which stems from a supplementary Higgs field,
introduced along with the usual Higgs doublet responsible for the electroweak
breaking and the masses of $W^{\pm}$ and $Z^{0}$. Yukawa interactions of the
two scalars generate the masses of the Standard Model leptons, neutrinos and a
new exotic fermion of the model. The vacuum expectation values of the Higgses
fix up two independent energy scales. One of them is the well-confirmed
electroweak scale, $246 \, \mbox{GeV}$, whereas the other one is set up by
adopting an experimental estimate for the $Z'$-mass.Comment: 11 pages, 2 figure
Questioning the recent observation of quantum Hawking radiation

A recent article [J. Steinhauer, Nat. Phys. 12, 959 (2016)] has reported the
observation of quantum Hawking radiation and its entanglement in an analogue
black hole. This paper analyses the published evidence, its consistency with
theoretical bounds and the statistical significance of the results. The
analysis raises severe doubts on the observation of Hawking radiation.Comment: Accepted by Annalen der Physik 5 September 2017; published
  electronically 26 March 2018 https://doi.org/10.1002/andp.20170011
Topological field theory and computing with instantons

Chern-Simons topological field theories TFTs are the only TFTs that have
already found application in the description of some exotic strongly-correlated
electron systems and the corresponding concept of topological quantum
computing. Here, we show that TFTs of another type, specifically the
gauge-field-less Witten-type TFTs known as topological sigma models, describe
the recently proposed digital memcomputing machines (DMMs) - engineered
dynamical systems with point attractors being the solutions of the
corresponding logic circuit that solves a specific task. This result derives
from the recent finding that any stochastic differential equation possesses a
topological supersymmetry, and the realization that the solution search by a
DMM proceeds via an instantonic phase. Certain TFT correlators in DMMs then
reveal the presence of a transient long-range order both in space and time,
associated with the effective breakdown of the topological supersymmetry by
instantons. The ensuing non-locality and the low dimensionality of instantons
are the physical reasons why DMMs can solve complex problems efficiently,
despite their non-quantum character. We exemplify these results with the
solution of prime factorization