pinecone/core-2020-05-10-deduplication huggingface dataset:
Algebraic description of G-flux in F-theory: new techniques for F-theory
  phenomenology

We give a global algebraic description of the four-form flux in F-theory. We
present how to compute its D3-tadpole and how to calculate the number of
four-dimensional chiral states at the intersection of 7-branes directly in
F-theory. We check that, in the weak coupling limit, we obtain the same results
as using perturbative type IIB string theory. We develop these techniques in
full generality. However, they can be readily applied to concrete models, as we
show in an explicit example.Comment: 7 pages, contribution to the proceedings of the "XVII European
  Workshop on String Theory 2011", Padova, Italy, 5-9 September 2011; to appear
  in Fortschritte der Physik, v2 refs adde
Generalized quark-antiquark potential in AdS/CFT

In this talk we present a family of Wilson loop operators which continuously interpolates between the 1/2 BPS line and the antiparallel lines, and can be thought of as calculating a generalization of the quark–antiquark potential for the gauge theory on S3 × R. We evaluate the first two orders of these loops perturbatively both in the gauge and string theory. We obtain analytical expressions in a systematic expansion around the 1/2 BPS configuration, and comment on possible all‐loop patterns for these Wilson loops
Quadratic deformation of Minkowski space

We present a deformation of the Minkowski space as embedded into the
conformal space (in the formalism of twistors) based in the quantum versions of
the corresponding kinematic groups. We compute explicitly the star product,
whose Poisson bracket is quadratic. We show that the star product although
defined on the polynomials can be extended differentiably. Finally we compute
the Eucliden and Minkowskian real forms of the deformation.Comment: Presented at XVII European Workshop on String Theory 2011. Padova
  (Italy) September 05-09; Fortschr. Phys. 1-7 (2012
A brief review on the Problem of Divergence in Krein Space Quantization

In this paper we have a brief review on the problem of divergence in quantum
field theory and its elimination using the method of Krein space quantization.
In this method, the auxiliary negative frequency states have been utilized, the
modes of which do not interact with the physical states and are not affected by
the physical boundary conditions. It is remarkable that Krein space
quantization is similar to Pauli-Villars regularization, so we can call it the
"Krein regularization". Considering the QED in Krein space quantization, it
could be shown that the theory is automatically regularized. Calculation of the
three primitive divergent integrals, the vacuum polarization, electron self
energy and vertex function using Krein space method leads to finite values,
since the infrared and ultraviolet divergencies do not appear. For another
example, the Casimir stress on a spherical shell in de Sitter spacetime for a
massless scalar field could be calculated using Krein space quantization.Comment: 6 pages, no figures. arXiv admin note: text overlap with
  arXiv:1109.2693, arXiv:hep-th/0511077 by other author
Freezing E3-brane instantons with fluxes

E3-instantons that generate non-perturbative superpotentials in IIB N=1
compactifications are more frequent than currently believed. Worldvolume fluxes
will typically lift the E3-brane geometric moduli and their fermionic
superpartners, leaving only the two required universal fermionic zero-modes. We
consistently incorporate SL(2, Z) monodromies and world-volume fluxes in the
effective theory of the E3-brane fermions and study the resulting zero-mode
spectrum, highlighting the relation between F-theory and perturbative IIB
results. This leads us to a IIB derivation of the index for generation of
superpotential terms, which reproduces and generalizes available results.
Furthermore, we show how worldvolume fluxes can be explicitly constructed in a
one-modulus compactification, such that an E3-instanton has exactly two
fermonic zero-modes. This construction is readily applicable to numerous
scenarios.Comment: 8 pages. Proceedings of the "XVII European Workshop on String Theory
  2011", Padova, Italy, 5-9 September 201
Asymptotically Schr\"odinger Space-Times

We first review how asymptotically Schr\"odinger space-times arise in a
natural way by performing a TsT transformation on asymptotically AdS
space-times and some of its consequences. We then give a coordinate independent
definition of a pure Schr\"odinger space-time in terms of an AdS metric and an
AdS null Killing vector. Then, by analogy with the AdS case, we provide a local
and coordinate independent definition of a Schr\"odinger boundary in terms of a
defining function. We use this to construct the Fefferman-Graham expansions of
locally Schr\"odinger space-times.Comment: 6 pages, based on a contribution to the Proceedings of the XVII
  European Workshop on String Theory (Padova, 5-9 September 2011
IIB Superfluid Flows

We construct holographic superfluid flow solutions in a five-dimensional
theory that arises as a consistent truncation of low energy type IIB string
theory. We then study the phase diagram of these systems in terms of the
temperature and superfluid velocity. Finally, we construct solutions
representing the ground state of these superfluids for velocities below a
critical value. These are charged anisotropic AdS domain walls that demonstrate
the emergence of quantum criticality in the IR.Comment: Contribution to the XVII European Workshop on String Theory 2011
  (Padova, September 2011
Holography and condensed matter

This is a short review of recent developments in the application of AdS/CFT
methods to some condensed matter problems. In particular we present the
holographic description of a local quantum critical state, related to
(non)-Fermi liquids and the strange metal, that appears in large N CFTs with a
gravity dual at finite density and zero temperature, and explore its properties
by probing it with fermionic operators. Further we discuss possible bosonic and
fermionic instabilities, leading to s-, p- or d-wave holographic
superconductors and "electron stars". Finally we present a realization of local
quantum criticality via an impurity problem.Comment: 11 pages, 4 figures; Contribution to the proceedings of the "XVII
  European Workshop on String Theory 2011", Padova, Italy, 5-9 September 2011;
  v2: ref adde
Completing the Web of $Z_3$ - Quotients of Complete Intersection
  Calabi-Yau Manifolds

We complete the study of smooth $Z_3$-quotients of complete intersection
Calabi-Yau threefolds by discussing the six new manifolds that admit free $Z_3$
actions that were discovered discovered recently by Braun. These manifolds were
missed in an earlier work and complete the web of smooth $Z_3$-quotients in a
nice way. We discuss the transitions between these manifolds and include also
the other manifolds of the web. This leads to the conclusion that the web of
$Z_3$-free quotients of complete intersection Calabi-Yau threefolds is
connected by conifold transitions.Comment: 30 pages with many colour figure
Unoriented D-brane instantons

We give a pedagogical introduction to D-brane instanton effects in vacuum
configurations with open and unoriented strings. We focus on quiver gauge
theories for unoriented D-branes at orbifold singularities and describe in some
detail the Z_3 case, where both `gauge' and `exotic' instantons can generate
non-perturbative super potentials, and the Z_5 case, where supersymmetry
breaking may arise from the combined effect of `gauge' instantons and a FI
D-term.Comment: 12 pages, 1 figure. Proceedings of the "XVII European Workshop on
  String Theory 2011", Padova, Italy, 5-9 September 201
Stepwise introduction of model complexity in a generalized master
  equation approach to time-dependent transport

We demonstrate that with a stepwise introduction of complexity to a model of
an electron system embedded in a photonic cavity and a carefully controlled
stepwise truncation of the ensuing many-body space it is possible to describe
the time-dependent transport of electrons through the system with a
non-Markovian generalized quantum master equation. We show how this approach
retains effects of an external magnetic field and the geometry of an
anisotropic electronic system. The Coulomb interaction between the electrons
and the full electromagnetic coupling between the electrons and the photons are
treated in a non-perturbative way using "exact numerical diagonalization".Comment: RevTeX, 14 pages with included eps figures, replaced to mend scaling
  in figure axes for time "t" and current "J
Dynamical stabilization and time in open quantum systems

The meaning of time in an open quantum system is considered under the
assumption that both, system and environment, are quantum mechanical objects.
The Hamilton operator of the system is non-Hermitian. Its imaginary part is the
time operator. As a rule, time and energy vary continuously when controlled by
a parameter. At high level density, where many states avoid crossing, a
dynamical phase transition takes place in the system under the influence of the
environment. It causes a dynamical stabilization of the system what can be seen
in many different experimental data. Due to this effect, time is bounded from
below: the decay widths (inverse proportional to the lifetimes of the states)
do not increase limitless. The dynamical stabilization is an irreversible
process.Comment: Contribution to the Special Issue "Quantum Physics with Non-Hermitian
  Operators: Theory and Experiment", Fortschritte der Physik - Progress of
  Physic
Avoided level crossings in open quantum systems

At high level density, two states avoid usually crossing at the critical
value $a_{\rm cr}$ of the parameter $a$ by which the system is controlled. The
wavefunctions of the two states are mixed in a finite parameter range around
$a_{\rm cr}$. This holds true for discrete states as well as for narrow
resonance states which are coupled via the environment of scattering
wavefunctions. We study the influence of avoided level crossings onto four
overlapping complex eigenvalues of a symmetric non-Hermitian operator. The
mixing of the two wavefunctions around $a_{\rm cr}$ is simulated, in each case,
by assuming a Gaussian distribution around $a_{\rm cr}$. At high level density,
the Gaussian distributions related to avoided crossings of different levels may
overlap. Here, new effects arise, especially from the imaginary part of the
coupling term via the environment. The results show, moreover, the influence of
symmetries onto the multi-level avoided crossing phenomenon.Comment: Contribution to the Special Issue "Quantum Physics with Non-Hermitian
  Operators: Theory and Experiment", Fortschritte der Physik - Progress of
  Physics 201
Equivalence of the effective Hamiltonian approach and the Siegert
  boundary condition for resonant states

Two theoretical methods of finding resonant states in open quantum systems,
namely the approach of the Siegert boundary condition and the Feshbach
formalism, are reviewed and shown to be algebraically equivalent to each other
for a simple model of the T-type quantum dot. It is stressed that the seemingly
Hermitian Hamiltonian of an open quantum system is implicitly non-Hermitian
outside the Hilbert space. The two theoretical approaches extract an explicitly
non-Hermitian effective Hamiltonian in a contracted space out of the seemingly
Hermitian (but implicitly non-Hermitian) full Hamiltonian in the
infinite-dimensional state space of an open quantum system.Comment: 11 pages, 3 figures, Conference proceedings "Quantum Physics with
  Non-Hermitian Operators" in Max-Planck-Institut f\"ur Physik komplexer
  Systeme in Dresden, 201
Neutron Resonance Data Exclude Random Matrix Theory

Almost since the time it was formulated, the overwhelming consensus has been
that random matrix theory (RMT) is in excellent agreement with neutron
resonance data. However, over the past few years, we have obtained new
neutron-width data at Oak Ridge and Los Alamos National Laboratories that are
in stark disagreement with this theory. We also have reanalyzed neutron widths
in the most famous data set, the nuclear data ensemble (NDE), and found that it
is seriously flawed, and, when analyzed carefully, excludes RMT with high
confidence. More recently, we carefully examined energy spacings for these same
resonances in the NDE using the $\Delta_{3}$ statistic. We conclude that the
data can be found to either confirm or refute the theory depending on which
nuclides and whether known or suspected p-wave resonances are included in the
analysis, in essence confirming results of our neutron-width analysis of the
NDE. We also have examined radiation widths resulting from our Oak Ridge and
Los Alamos measurements, and find that in some cases they do not agree with
RMT. Although these disagreements presently are not understood, they could have
broad impact on basic and applied nuclear physics, from nuclear astrophysics to
nuclear criticality safety.Comment: 14 pages, 9 figures, submitted to special issue of Fortschritte Der
  Physik, Quantum Physics with Non-Hermitian Operator
Non-Hermitian approach for modeling of noise-assisted quantum electron
  transfer in photosynthetic complexes

We model the quantum electron transfer (ET) in the photosynthetic reaction
center (RC), using a non-Hermitian Hamiltonian approach. Our model includes (i)
two protein cofactors, donor and acceptor, with discrete energy levels and (ii)
a third protein pigment (sink) which has a continuous energy spectrum.
Interactions are introduced between the donor and acceptor, and between the
acceptor and the sink, with noise acting between the donor and acceptor. The
noise is considered classically (as an external random force), and it is
described by an ensemble of two-level systems (random fluctuators). Each
fluctuator has two independent parameters, an amplitude and a switching rate.
We represent the noise by a set of fluctuators with fitting parameters
(boundaries of switching rates), which allows us to build a desired spectral
density of noise in a wide range of frequencies. We analyze the quantum
dynamics and the efficiency of the ET as a function of (i) the energy gap
between the donor and acceptor, (ii) the strength of the interaction with the
continuum, and (iii) noise parameters. As an example, numerical results are
presented for the ET through the active pathway in a quinone-type photosystem
II RC.Comment: 15 pages, 8 figure
Non-Markovian electron dynamics in nanostructures coupled to dissipative
  contacts

In quasiballistic semiconductor nanostructures, carrier exchange between the
active region and dissipative contacts is the mechanism that governs
relaxation. In this paper, we present a theoretical treatment of transient
quantum transport in quasiballistic semiconductor nanostructures, which is
based on the open system theory and valid on timescales much longer than the
characteristic relaxation time in the contacts. The approach relies on a model
interaction between the current-limiting active region and the contacts, given
in the scattering-state basis. We derive a non-Markovian master equation for
the irreversible evolution of the active region's many-body statistical
operator by coarse-graining the exact dynamical map over the contact relaxation
time. In order to obtain the response quantities of a nanostructure under bias,
such as the potential and the charge and current densities, the non-Markovian
master equation must be solved numerically together with the Schr\"{o}dinger,
Poisson, and continuity equations. We discuss how to numerically solve this
coupled system of equations and illustrate the approach on the example of a
silicon nin diode.Comment: FdP Special Issue: Quantum Physics with non-Hermitian Operators:
  Theory and Experiment. arXiv admin note: text overlap with arXiv:0801.401
Duality orbits of non-geometric fluxes

Compactifications in duality covariant constructions such as generalised
geometry and double field theory have proven to be suitable frameworks to
reproduce gauged supergravities containing non-geometric fluxes. However, it is
a priori unclear whether these approaches only provide a reformulation of old
results, or also contain new physics. To address this question, we classify the
T- and U-duality orbits of gaugings of (half-)maximal supergravities in
dimensions seven and higher. It turns out that all orbits have a geometric
supergravity origin in the maximal case, while there are non-geometric orbits
in the half-maximal case. We show how the latter are obtained from
compactifications of double field theory.Comment: 39 pages, 1 figure, 6 tables; v2: refs added, published versio
Interplay of superradiance and disorder in the Anderson Model

Using a non-Hermitian Hamiltonian approach to open systems, we study the
interplay of disorder and superradiance in a one-dimensional Anderson model.
Analyzing the complex eigenvalues of the non-Hermitian Hamiltonian, a
transition to a superradiant regime is shown to occur. As an effect of openness
the structure of eigenstates undergoes a strong change in the superradiant
regime: we show that the sensitivity to disorder of the superradiant and the
subradiant subspaces is very different; superradiant states remain delocalized
as disorder increases, while subradiant states are sensitive to the degree of
disorder.Comment: 7 pages, submitted to the special issue on "Physics with
  non-Hermitian operators: Theory and Experiment" of the journal "Fortschritte
  der Physik - Progress of Physics
Non-Geometric Fluxes in Supergravity and Double Field Theory

In this paper we propose ten-dimensional realizations of the non-geometric
fluxes Q and R. In particular, they appear in the NSNS Lagrangian after
performing a field redefinition that takes the form of a T-duality
transformation. Double field theory simplifies the computation of the field
redefinition significantly, and also completes the higher-dimensional picture
by providing a geometrical role for the non-geometric fluxes once the winding
derivatives are taken into account. The relation to four-dimensional gauged
supergravities, together with the global obstructions of non-geometry, are
discussed.Comment: 43 page
Toric bases for 6D F-theory models

We find all smooth toric bases that support elliptically fibered Calabi-Yau
threefolds, using the intersection structure of the irreducible effective
divisors on the base. These bases can be used for F-theory constructions of
six-dimensional quantum supergravity theories. There are 61,539 distinct
possible toric bases. The associated 6D supergravity theories have a number of
tensor multiplets ranging from 0 to 193. For each base an explicit Weierstrass
parameterization can be determined in terms of the toric data. The toric
counting of parameters matches with the gravitational anomaly constraint on
massless fields. For bases associated with theories having a large number of
tensor multiplets, there is a large non-Higgsable gauge group containing
multiple irreducible gauge group factors, particularly those having algebras
e_8, f_4 and (g_2 + su(2)) with minimal (non-Higgsable) matter.Comment: 39 pages, 13 figures, one appendix; ancillary data file contains list
  of 61,539 bases; v2: minor correctio
Astrophysical Evidence for the Non-Hermitian but $PT$-symmetric
  Hamiltonian of Conformal Gravity

In this review we discuss the connection between two seemingly disparate
topics, macroscopic gravity on astrophysical scales and Hamiltonians that are
not Hermitian but $PT$ symmetric on microscopic ones. In particular we show
that the quantum-mechanical unitarity problem of the fourth-order derivative
conformal gravity theory is resolved by recognizing that the scalar product
appropriate to the theory is not the Dirac norm associated with a Hermitian
Hamiltonian but is instead the norm associated with a non-Hermitian but
$PT$-symmetric Hamiltonian. Moreover, the fourth-order theory Hamiltonian is
not only not Hermitian, it is not even diagonalizable, being of Jordan-block
form. With $PT$ symmetry we establish that conformal gravity is consistent at
the quantum-mechanical level. In consequence, we can apply the theory to data,
to find that the theory is capable of naturally accounting for the systematics
of the rotation curves of a large and varied sample of 138 spiral galaxies
without any need for dark matter. The success of the fits provides evidence for
the relevance of non-diagonalizable but $PT$-symmetric Hamiltonians to physics.Comment: LaTex, 15 pages, 21 figures. Expanded version of talks given at the
  International Seminar and Workshop "Quantum Physics with Non-Hermitian
  Operators", Dresden, June 2011 and the Symposium "PT Quantum Mechanics 2011",
  Heidelberg, September 2011. Prepared for a Special Issue of Fortschritte der
  Physik - Progress of Physics on "Quantum Physics with Non-Hermitian
  Operators: Theory and Experiment
Microwave experiments using open chaotic cavities in the realm of the effective Hamiltonian formalism

published online 2012-07-30International audienceThe description of open quantum system successfully uses the concept of the effective Hamiltonian, which takes into account the coupling to the environment. The concept can be extended to classical waves. Exper- imentally, classical waves are very convenient as they allow to control boundaries, coupling and absorption. We combine here recent works with microwaves investigating properties of open systems which can be de- scribed by an effective Hamiltonian. This ranges from spectral properties like modifications to level dynam- ics, width distribution and coupling fidelity to spatial properties like intensity distributions and complexness parameter which describes the non-orthogonality of eigenfunctions
Brane singularities with mixtures in the bulk

By extending previous analysis of the authors, a systematic study of the
singularity structure and possible asymptotic behaviors of five-dimensional
braneworld solutions is performed in the case where the bulk is a mixture of an
analog of perfect fluid (with a density and pressure depending on the extra
coordinate) and a massless scalar field. The two bulk components interact by
exchanging energy so that the total energy is conserved. In a particular range
of the interaction parameters, we find flat brane general solutions avoiding
the singularity at finite distance from the brane, in the same region of the
equation of state constant parameter $\gamma=P/\rho$ that we found previously
in the absence of the bulk scalar field $(-1<\gamma<-1/2)$.Comment: 48 page
Status of three-neutrino oscillation parameters

Here we review the current status of global fits to neutrino oscillation data within the three-flavour framework. In our analysis we include the most recent data from solar and atmospheric neutrino experiments as well as the latest results from the long-baseline accelerator neutrino experiments and the recent measurements of reactor neutrino disappearance reported by Double Chooz, Daya Bay and RENO. We present updated determinations for the two neutrino mass splittings and the three mixing angles responsible for neutrino oscillations that, for the first time, have all been measured with 1 sigma accuracies ranging from 3 to 15%. A weak sensitivity for the CP violating phase is also reported from the global analysis