pinecone/core-2020-05-10-deduplication huggingface dataset:
The quantum ferromagnetic transition in a clean Kondo lattice is
  discontinuous

The Kondo-lattice model, which couples a lattice of localized magnetic
moments to conduction electrons, is often used to describe heavy-fermion
systems. Because of the interplay between Kondo physics and magnetic order it
displays very complex behavior and is notoriously hard to solve. The
ferromagnetic Kondo-lattice model, with a ferromagnetic coupling between the
local moments, describes a phase transition from a paramagnetic phase to a
ferromagnetic one as a function of either temperature or the ferromagnetic
local-moment coupling. At zero temperature, this is a quantum phase transition
that has received considerable attention. It has been theoretically described
to be continuous, or second order. Here we show that this belief is mistaken;
in the absence of quenched disorder the quantum phase transition is first
order, in agreement with experiments, as is the corresponding transition in
other metallic ferromagnets.Comment: 8pp., 2 figs., contribution to FQMT'1
The Flux-Scaling Scenario: De Sitter Uplift and Axion Inflation

Non-geometric flux-scaling vacua provide promising starting points to realize
axion monodromy inflation via the F-term scalar potential. We show that these
vacua can be uplifted to Minkowski and de Sitter by adding an anti D3-brane or
a D-term containing geometric and non-geometric fluxes. These uplifted
non-supersymmetric models are analyzed with respect to their potential to
realize axion monodromy inflation self-consistently. Admitting rational values
of the fluxes, we construct examples with the required hierarchy of mass
scales.Comment: 30 pages, 7 figures, v2: refs adde
Non-abelian T-duality of Pilch-Warner background

In this work we obtain the non-abelian T-dual geometry of the well-known
Pilch-Warner supergravity solution in its infrared point. We derive the dual
metric and the NS two-form by gauging the isometry group of the initial theory
and integrating out the introduced auxiliary gauge fields. Then we use the
Fourier-Mukai transform from algebraic geometry to find the transformation
rules of the R-R fields. The dual background preserves the $\mathcal{N}=1$
supersymmetry of the original one due to the fact that the Killing spinor does
not depend on the directions on which the N-AT-D is performed. Finally, we
consider two different pp-wave limits of the T-dual geometry by performing
Penrose limits for two light-like geodesics.Comment: 23 pages; v2: minor corrections, comments and references added; v3:
  supersymmetric analysis and pp-wave limits added, published versio
Effects of excited state quantum phase transitions on system dynamics

This work is concerned with the excited state quantum phase transitions
(ESQPTs) defined in Ann.Phys. 323, 1106 (2008). In many-body models that
exhibit such transitions, the ground state quantum phase transition (QPT)
occurs in parallel with a singularity in the energy spectrum that propagates to
higher energies as the control parameter increases beyond the QPT critical
point. The analysis of the spectrum has been a main tool for the detection of
these ESQPTs. Studies of the effects of this transition on the system dynamics
are more limited. Here, we extend our previous works and show that the
evolution of an initial state with energy close to the ESQPT critical point may
be extremely slow. This result is surprising, because it may take place in
systems with long-range interactions, where the dynamics is usually expected to
be very fast. A timely example is the one-dimensional spin-1/2 model with
infinite-range Ising interaction studied in experiments with ion traps. Its
Hamiltonian has a U(2) algebraic structure. More generally, the slow dynamics
described here occurs in two-level bosonic or fermionic models with pairing
interactions and a U(v+1) Hamiltonian exhibiting a QPT between its limiting
U(v) and SO(v+1) dynamical symmetries. In this work, we compare the results for
v=1, 2, and 3.Comment: 6 pages, 4 figures, accepted at the FQMT15 special volume of the
  Fortschritte der Physi
Underlying non-Hermitian character of the Born rule in open quantum
  systems

The absolute value squared of the probability amplitude corresponding to the
overlap of an initial state with a continuum wave solution to the Schr\"odinger
equation of the problem, has the physical interpretation provided by the Born
rule. Here, it is shown that for an open quantum system, the above probability
may be written in an exact analytical fashion as an expansion in terms of the
non-Hermitian resonance (quasinormal) states and complex poles to the problem
which provides an underlying non-Hermitian character of the Born rule.Comment: 8 pages, 2 figure
Probabilistic Foundations of Contextuality

Contextuality is usually defined as absence of a joint distribution for a set
of measurements (random variables) with known joint distributions of some of
its subsets. However, if these subsets of measurements are not disjoint,
contextuality is mathematically impossible even if one generally allows (as one
must) for random variables not to be jointly distributed. To avoid
contradictions one has to adopt the Contextuality-by-Default approach:
measurements made in different contexts are always distinct and stochastically
unrelated to each other. Contextuality is reformulated then in terms of the
(im)possibility of imposing on all the measurements in a system a joint
distribution of a particular kind: such that any measurements of one and the
same property made in different contexts satisfy a specified property,
$\mathcal{C}$. In the traditional analysis of contextuality $\mathcal{C}$ means
"are equal to each other with probability 1". However, if the system of
measurements violates the "no-disturbance principle", due to signaling or
experimental biases, then the meaning of $\mathcal{C}$ has to be generalized,
and the proposed generalization is "are equal to each other with maximal
possible probability" (applied to any set of measurements of one and the same
property). This approach is illustrated on arbitrary systems of binary
measurements, including most of quantum systems of traditional interest in
contextuality studies (irrespective of whether "no-disturbance" principle holds
in them).Comment: To be published in Fortschritte der Physik - Progress of Physics. The
  last version corrects a typ
The role of average time dependence on the relaxation of excited
  electron populations in nonequilibrium many-body physics

We examine the exact equation of motion for the relaxation of populations of
strongly correlated electrons after a nonequilibrium excitation by a pulsed
field, and prove that the populations do not change when the Green's functions
have no average time dependence. We show how the average time dependence enters
into the equation of motion to lowest order and describe what governs the
relaxation process of the electron populations in the long-time limit. While
this result may appear, on the surface, to be required by any steady-state
solution, the proof is nontrivial, and provides new critical insight into how
nonequilibrium populations relax, which goes beyond the assumption that they
thermalize via a simple relaxation rate determined by the imaginary part of the
self-energy, or that they can be described by a quasi-equilibrium condition
with a Fermi-Dirac distribution and a time-dependent temperature. We also
discuss the implications of this result to approximate theories, which may not
satisfy the exact relation in the equation of motion.Comment: (8 pages, 5 figures, conference proceedings for FQMT15), published in
  Fortschritte der Physi
Scale Invariance at low accelerations (aka MOND) and the dynamical
  anomalies in the Universe

Galactic systems, and the Universe at large, exhibit large dynamical
anomalies: The observed matter in them falls very short of providing enough
gravity to account for their dynamics. The mainstream response to this
conundrum is to invoke large quantities of `dark matter' -- which purportedly
supplies the needed extra gravity -- and also of `dark energy', to account for
further anomalies in cosmology, such as the observed, accelerated expansion.
The MOND paradigm offers a different solution: a breakdown of standard dynamics
(gravity and/or inertia) in the limit of low accelerations -- below some
acceleration $a_0$. In this limit, dynamics become space-time scale invariant,
and is controlled by a gravitational constant $\mathcal{A}_0\equiv Ga_0$, which
replaces Newton's $G$. With the new dynamics, the various detailed
manifestations of the anomalies in galaxies are predicted with no need for dark
matter. The cosmological anomalies could, but need not have to do with small
accelerations. For example, the need for dark matter in accounting for the
expansion history of the Universe is eliminated if the relevant gravitational
constant is $\approx 2\pi G$. Such a `renormalization' of $G$ could be a
dimensionless parameter of a MOND theory. The constant $a_0$ turns out to carry
cosmological connotations, in that $2\pi a_0\approx cH_0\approx
c^2(\Lambda/3)^{1/2}$, where $H_0$ is the present expansion rate of the
Universe, and $\Lambda$ the measured `cosmological constant'. There are MOND
theories in which this `coincidence' is natural. I draw on enlightening
historical and conceptual analogies from quantum theory to limelight aspects of
MOND. I also explain how MOND may have strong connections with effects of the
quantum vacuum on local dynamics.Comment: 13 pages, 4 figures. Based on an invited talk at: `Frontiers of
  Quantum and Mesoscopic Thermodynamics - FQMT15', Prague, 2015. Somewhat
  expande
Negative Entropies in Casimir and Casimir-Polder Interactions

It has been increasingly becoming clear that Casimir and Casimir-Polder
entropies may be negative in certain regions of temperature and separation. In
fact, the occurrence of negative entropy seems to be a nearly ubiquitous
phenomenon. This is most highlighted in the quantum vacuum interaction of a
nanoparticle with a conducting plate or between two nanoparticles. It has been
argued that this phenomenon does not violate physical intuition, since the
total entropy, including the self-entropies of the plate and the nanoparticle,
should be positive. New calculations, in fact, seem to bear this out at least
in certain cases.Comment: 8 pages, 12 figures, extended version of talk at Frontiers of Quantum
  and Mesoscopic Thermodynamics, Prague, 201
How Zwicky already ruled out modified gravity theories without dark
  matter

Various theories, such as MOND, MOG, Emergent Gravity and $f(R)$ theories
avoid dark matter by assuming a change in General Relativity and/or in Newton's
law. Galactic rotation curves are typically described well. Here the
application to galaxy clusters is considered, focussed on the good lensing and
X-ray data for A1689. As a start, the no-dark-matter case is confirmed to work
badly: the need for dark matter starts near the cluster centre, where Newton's
law is still supposed to be valid. This leads to the conundrum discovered by
Zwicky, which is likely only solvable in his way, namely by assuming additional
(dark) matter. Neutrinos with eV masses serve well without altering the
successes in (dwarf) galaxies.Comment: 10 pages, 2 figures. Matches published versio
Current Noise in Tunnel Junctions

We study current fluctuations in tunnel junctions driven by a voltage source.
The voltage is applied to the tunneling element via an impedance providing an
electromagnetic environment of the junction. We use circuit theory to relate
the fluctuations of the current flowing in the leads of the junction with the
voltage fluctuations generated by the environmental impedance and the
fluctuations of the tunneling current. The spectrum of current fluctuations is
found to consist of three parts: a term arising from the environmental
Johnson-Nyquist noise, a term due to the shot noise of the tunneling current
and a third term describing the cross-correlation between these two noise
sources. Our phenomenological theory reproduces previous results based on the
Hamiltonian model for the dynamical Coulomb blockade and provides a simple
understanding of the current fluctuation spectrum in terms of circuit theory
and properties of the average current. Specific results are given for a tunnel
junction driven through a resonator.Comment: 8 pages, 4 figure
Detector's quantum backaction effects on a mesoscopic conductor and fluctuation-dissipation relation

When measuring quantum mechanical properties of charge transport in mesoscopic conductors, backaction effects occur. We consider a measurement setup with an elementary quantum circuit, composed of an inductance and a capacitor, as detector of the current flowing in a nearby quantum point contact. A quantum Langevin equation for the detector variable including backaction effects is derived. Differences with the quantum Langevin equation obtained in linear response are pointed out. In this last case, a relation between fluctuations and dissipation is obtained, provided that an effective temperature of the quantum point contact is defined
Black Hole Based Quantum Computing in Labs and in the Sky

Analyzing some well established facts, we give a model-independent
parameterization of black hole quantum computing in terms of a set of macro and
micro quantities and their relations. These include the relations between the
extraordinarily-small energy gap of black hole qubits and important time-scales
of information-processing, such as, scrambling time and Page's time. We then
show, confirming and extending previous results, that other systems of nature
with identical quantum informatics features are attractive Bose-Einstein
systems at the critical point of quantum phase transition. Here we establish a
complete isomorphy between the quantum computational properties of these two
systems. In particular, we show that the quantum hair of a critical condensate
is strikingly similar to the quantum hair of a black hole. Irrespectively
whether one takes the similarity between the two systems as a remarkable
coincidence or as a sign of a deeper underlying connection, the following is
evident. Black holes are not unique in their way of quantum information
processing and we can manufacture black hole based quantum computers in labs by
taking advantage of quantum criticality.Comment: 25 pages, late
Time-resolved statistics of photon pairs in two-cavity Josephson
  photonics

We analyze the creation and emission of pairs of highly nonclassical
microwave photons in a setup where a voltage-biased Josephson junction is
connected in series to two electromagnetic oscillators. Tuning the external
voltage such that the Josephson frequency equals the sum of the two mode
frequencies, each tunneling Cooper pair creates one additional photon in both
of the two oscillators. The time-resolved statistics of photon emission events
from the two oscillators is investigated by means of single- and
cross-oscillator variants of the second-order correlation function
$g^{(2)}(\tau)$ and the waiting-time distribution $w(\tau)$. They provide
insight into the strongly correlated quantum dynamics of the two oscillator
subsystems and reveal a rich variety of quantum features of light including
strong antibunching and the presence of negative values in the Wigner function.Comment: 9 pages, 7 figures; invited contribution to special volume "FQMT'15:
  Frontiers of Quantum and Mesoscopic Thermodynamics (Prague, Czech Republic,
  27 July - 1 August 2015)
Analysis of universality in transient dynamics of coherent electronic
  transport

We analyze the time-dependent full-counting statistics of charges transmitted
through a quantum dot in the coherent regime. The generating function for the
time-dependent charge transfer statistics is evaluated numerically by
discretizing the Keldysh time contour, which allows us to compute the higher
order charge and current cumulants. We also develop an analytic expression for
all order cumulants at any time given as a function of the zeros of the
generating function, finding that the short time universality is due to the
presence of a dominant single zero. The robustness of the universal features at
short times is studied in both the sequential and coherent regimes.Comment: 8 pages, 6 figures, invited contribution to special volume "FQMT'15:
  Frontiers of Quantum and Mesoscopic Thermodynamics (Prague, Czech Republic,
  27 July - 1 August 2015)
F-theory and Unpaired Tensors in 6D SCFTs and LSTs

We investigate global symmetries for 6D SCFTs and LSTs having a single
"unpaired" tensor, that is, a tensor with no associated gauge symmetry. We
verify that for every such theory built from F-theory whose tensor has Dirac
self-pairing equal to -1, the global symmetry algebra is a subalgebra of
$\mathfrak{e}_8$. This result is new if the F-theory presentation of the theory
involves a one-parameter family of nodal or cuspidal rational curves (i.e.,
Kodaira types $I_1$ or $II$) rather than elliptic curves (Kodaira type $I_0$).
For such theories, this condition on the global symmetry algebra appears to
fully capture the constraints on coupling these theories to others in the
context of multi-tensor theories. We also study the analogous problem for
theories whose tensor has Dirac self-pairing equal to -2 and find that the
global symmetry algebra is a subalgebra of $\mathfrak{su}(2)$. However, in this
case there are additional constraints on F-theory constructions for coupling
these theories to others.Comment: 21 page
Continuous dynamical decoupling utilizing time-dependent detuning

Resilience to noise and to decoherence processes is an important ingredient
for the implementation of quantum information processing, and quantum
technologies. To this end, techniques such as pulsed and continuous dynamical
decoupling have been proposed to reduce noise effects. In this paper, we
suggest a new approach to implementing continuous dynamical decoupling
techniques, that uses an extra control parameter; namely, the ability to shape
the time dependence of the detuning. This approach reduces the complexity of
the experimental setup, such that we are only left with noise originating from
the frequency of the driving field, which is much more robust than the
amplitude (Rabi frequency) noise. As an example, we show that our technique can
be utilized for improved sensing
Quantum Holonomy Theory

We present quantum holonomy theory, which is a non-perturbative theory of
quantum gravity coupled to fermionic degrees of freedom. The theory is based on
a C*-algebra that involves holonomy-diffeomorphisms on a 3-dimensional manifold
and which encodes the canonical commutation relations of canonical quantum
gravity formulated in terms of Ashtekar variables. Employing a Dirac type
operator on the configuration space of Ashtekar connections we obtain a
semi-classical state and a kinematical Hilbert space via its GNS construction.
We use the Dirac type operator, which provides a metric structure over the
space of Ashtekar connections, to define a scalar curvature operator, from
which we obtain a candidate for a Hamilton operator. We show that the classical
Hamilton constraint of general relativity emerges from this in a semi-classical
limit and we then compute the operator constraint algebra. Also, we find states
in the kinematical Hilbert space on which the expectation value of the Dirac
type operator gives the Dirac Hamiltonian in a semi-classical limit and thus
provides a connection to fermionic quantum field theory. Finally, an
almost-commutative algebra emerges from the holonomy-diffeomorphism algebra in
the same limit.Comment: 76 pages, 6 figure
Enhanced gauge symmetry in 6D F-theory models and tuned elliptic
  Calabi-Yau threefolds

We systematically analyze the local combinations of gauge groups and matter
that can arise in 6D F-theory models over a fixed base. We compare the
low-energy constraints of anomaly cancellation to explicit F-theory
constructions using Weierstrass and Tate forms, and identify some new local
structures in the "swampland' of 6D supergravity and SCFT models that appear
consistent from low-energy considerations but do not have known F-theory
realizations. In particular, we classify and carry out a local analysis of all
enhancements of the irreducible gauge and matter contributions from
"non-Higgsable clusters," and on isolated curves and pairs of intersecting
rational curves of arbitrary self-intersection. Such enhancements correspond
physically to unHiggsings, and mathematically to tunings of the Weierstrass
model of an elliptic CY threefold. We determine the shift in Hodge numbers of
the elliptic threefold associated with each enhancement. We also consider local
tunings on curves that have higher genus or intersect multiple other curves,
codimension two tunings that give transitions in the F-theory matter content,
tunings of abelian factors in the gauge group, and generalizations of the
"$E_8$" rule to include tunings and curves of self-intersection zero. These
tools can be combined into an algorithm that in principle enables a finite and
systematic classification of all elliptic CY threefolds and corresponding 6D
F-theory SUGRA models over a given compact base (modulo some technical caveats
in various special circumstances), and are also relevant to the classification
of 6D SCFT's. To illustrate the utility of these results, we identify some
large example classes of known CY threefolds in the Kreuzer-Skarke database as
Weierstrass models over complex surface bases with specific simple tunings, and
we survey the range of tunings possible over one specific base.Comment: 101 pages, 3 figures, 25 tables; v2: references added, some technical
  corrections, minor typos correcte
Advances in quantum control of three-level superconducting circuit
  architectures

Advanced control in Lambda ($\Lambda$) scheme of a solid state architecture
of artificial atoms and quantized modes would allow the translation to the
solid-state realm of a whole class of phenomena from quantum optics, thus
exploiting new physics emerging in larger integrated quantum networks and for
stronger couplings. However control solid-state devices has constraints coming
from selection rules, due to symmetries which on the other hand yield
protection from decoherence, and from design issues, for instance that coupling
to microwave cavities is not directly switchable. We present two new schemes
for the $\Lambda$-STIRAP control problem with the constraint of one or two
classical driving fields being always-on. We show how these protocols are
converted to apply to circuit-QED architectures. We finally illustrate an
application to coherent spectroscopy of the so called ultrastrong atom-cavity
coupling regime.Comment: 9 pages, 5 figures. Received 27 June 2016, accepted 23 September 201