pinecone/core-2020-05-10-deduplication huggingface dataset:
Scaling Flows and Dissipation in the Dilute Fermi Gas at Unitarity

We describe recent attempts to extract the shear viscosity of the dilute
Fermi gas at unitarity from experiments involving scaling flows. A scaling flow
is a solution of the hydrodynamic equations that preserves the shape of the
density distribution. The scaling flows that have been explored in the
laboratory are the transverse expansion from a deformed trap ("elliptic flow"),
the expansion from a rotating trap, and collective oscillations. We discuss
advantages and disadvantages of the different experiments, and point to
improvements of the theoretical analysis that are needed in order to achieve
definitive results. A conservative bound based on the current data is that the
minimum of the shear viscosity to entropy density ration is that eta/s is less
or equal to 0.5 hbar/k_B.Comment: 32 pages, prepared for "BCS-BEC crossoverand the Unitary Fermi Gas",
  Lecture Notes in Physics, W. Zwerger (editor), Fig. 5 corrected, note added;
  final version, corrected typo in equ. 9
Crossovers in Unitary Fermi Systems

Universality and crossover is described for attractive and repulsive
interactions where, respectively, the BCS-BEC crossover takes place and a
ferromagnetic phase transition is claimed. Crossovers are also described for
optical lattices and multicomponent systems. The crossovers, universal
parameters and phase transitions are described within the Leggett and NSR
models and calculated in detail within the Jastrow-Slater approximation. The
physics of ultracold Fermi atoms is applied to neutron, nuclear and quark
matter, nuclei and electrons in solids whenever possible. Specifically, the
differences between optical lattices and cuprates is discussed w.r.t.
antiferromagnetic, d-wave superfluid phases and phase separation.Comment: 50 pages, 15 figures. Contribution to Lecture Notes in Physics
  "BCS-BEC crossover and the Unitary Fermi Gas" edited by W. Zwerge
Dilute Fermi and Bose Gases

I give a unified perspective on the properties of a variety of quantum
liquids using the theory of quantum phase transitions. A central role is played
by a zero density quantum critical point which is argued to control the
properties of the dilute gas. An exact renormalization group analysis of such
quantum critical points leads to a computation of the universal properties of
the dilute Bose gas and the spinful Fermi gas near a Feshbach resonance.Comment: 28 pages, 8 figures; adapted from Chapter 16 of Quantum Phase
  Transitions, Second Edition (see
  http://sachdev.physics.harvard.edu/qptweb/toc.html); contribution to Lecture
  Notes in Physics, "BCS-BEC crossover and the Unitary Fermi Gas" edited by W.
  Zwerge
Evaluating Interaction of MAS Providing Context-Aware Services

Proceeding of: 5th KES International Conference, KES-AMSTA 2011, Manchester, UK, June 29 – July 1, 2011Much effort has been spent on suggesting and implementing new architectures of MAS to specific domains. Often each new architecture is not even compared to any existing architectures in order to evaluate their potential benefits. The evaluation of Multi-Agent Systems (MAS) is a complex problem and it does not have a single form. The present work follows the research line of considering the agent interaction as the main evaluation criteria, the most important characteristic of any complex software as autonomous agents according to [9]. So, in this paper, we have suggested an assignment of evaluation values to Agents interaction in an specific MAS architecture for providing context services by means of conversational agents. This evaluation is mainly based on the relevance of the messages content brought by an interaction. For dependant nature of the relevance of the messages, the valuation has to be adhoc, but our paper provides an example of how interesting is this alternative in order to evaluate any MAS architecture theoretically.Funded by projects CICYT TIN2008-06742-C02-02/TSI, CICYT TEC2008-06732-
C02-02/TEC, SINPROB, CAM MADRINET S-0505/TIC/0255, and DPS2008-07029-
C02-02
Linear-Space Approximate Distance Oracles for Planar, Bounded-Genus, and
  Minor-Free Graphs

A (1 + eps)-approximate distance oracle for a graph is a data structure that
supports approximate point-to-point shortest-path-distance queries. The most
relevant measures for a distance-oracle construction are: space, query time,
and preprocessing time. There are strong distance-oracle constructions known
for planar graphs (Thorup, JACM'04) and, subsequently, minor-excluded graphs
(Abraham and Gavoille, PODC'06). However, these require Omega(eps^{-1} n lg n)
space for n-node graphs. We argue that a very low space requirement is
essential. Since modern computer architectures involve hierarchical memory
(caches, primary memory, secondary memory), a high memory requirement in effect
may greatly increase the actual running time. Moreover, we would like data
structures that can be deployed on small mobile devices, such as handhelds,
which have relatively small primary memory. In this paper, for planar graphs,
bounded-genus graphs, and minor-excluded graphs we give distance-oracle
constructions that require only O(n) space. The big O hides only a fixed
constant, independent of \epsilon and independent of genus or size of an
excluded minor. The preprocessing times for our distance oracle are also faster
than those for the previously known constructions. For planar graphs, the
preprocessing time is O(n lg^2 n). However, our constructions have slower query
times. For planar graphs, the query time is O(eps^{-2} lg^2 n). For our
linear-space results, we can in fact ensure, for any delta > 0, that the space
required is only 1 + delta times the space required just to represent the graph
itself
Buyback Problem - Approximate matroid intersection with cancellation
  costs

In the buyback problem, an algorithm observes a sequence of bids and must
decide whether to accept each bid at the moment it arrives, subject to some
constraints on the set of accepted bids. Decisions to reject bids are
irrevocable, whereas decisions to accept bids may be canceled at a cost that is
a fixed fraction of the bid value. Previous to our work, deterministic and
randomized algorithms were known when the constraint is a matroid constraint.
We extend this and give a deterministic algorithm for the case when the
constraint is an intersection of $k$ matroid constraints. We further prove a
matching lower bound on the competitive ratio for this problem and extend our
results to arbitrary downward closed set systems. This problem has applications
to banner advertisement, semi-streaming, routing, load balancing and other
problems where preemption or cancellation of previous allocations is allowed
Advice coins for classical and quantum computation

We study the power of classical and quantum algorithms equipped with nonuniform advice, in the form of a coin whose bias encodes useful information. This question takes on particular importance in the quantum case, due to a surprising result that we prove: a quantum finite automaton with just two states can be sensitive to arbitrarily small changes in a coin’s bias. This contrasts with classical probabilistic finite automata, whose sensitivity to changes in a coin’s bias is bounded by a classic 1970 result of Hellman and Cover.
Despite this finding, we are able to bound the power of advice coins for space-bounded classical and quantum computation. We define the classes BPPSPACE/coin and BQPSPACE/coin, of languages decidable by classical and quantum polynomial-space machines with advice coins. Our main theorem is that both classes coincide with PSPACE/poly. Proving this result turns out to require substantial machinery. We use an algorithm due to Neff for finding roots of polynomials in NC; a result from algebraic geometry that lower-bounds the separation of a polynomial’s roots; and a result on fixed-points of superoperators due to Aaronson and Watrous, originally proved in the context of quantum computing with closed timelike curves
Constructing differential categories and deconstructing categories of games

We present an abstract construction for building differential categories useful to model resource sensitive calculi, and we apply it to categories of games. In one instance, we recover a category previously used to give a fully abstract model of a nondeterministic imperative language. The construction exposes the differential structure already present in this model. A second instance corresponds to a new Cartesian differential category of games. We give a model of a Resource PCF in this category and show that it enjoys the finite definability property. Comparison with a relational semantics reveals that the latter also possesses this property and is fully abstract
On the relation between Differential Privacy and Quantitative Information Flow

International audienceDifferential privacy is a notion that has emerged in the community of statistical databases, as a response to the problem of protecting the privacy of the database's participants when performing statistical queries. The idea is that a randomized query satisfies differential privacy if the likelihood of obtaining a certain answer for a database $x$ is not too different from the likelihood of obtaining the same answer on adjacent databases, i.e. databases which differ from $x$ for only one individual. Information flow is an area of Security concerned with the problem of controlling the leakage of confidential information in programs and protocols. Nowadays, one of the most established approaches to quantify and to reason about leakage is based on the Rényi min entropy version of information theory. In this paper, we analyze critically the notion of differential privacy in light of the conceptual framework provided by the Rényi min information theory. We show that there is a close relation between differential privacy and leakage, due to the graph symmetries induced by the adjacency relation. Furthermore, we consider the utility of the randomized answer, which measures its expected degree of accuracy. We focus on certain kinds of utility functions called ''binary'', which have a close correspondence with the Rényi min mutual information. Again, it turns out that there can be a tight correspondence between differential privacy and utility, depending on the symmetries induced by the adjacency relation and by the query. Depending on these symmetries we can also build an optimal-utility randomization mechanism while preserving the required level of differential privacy. Our main contribution is a study of the kind of structures that can be induced by the adjacency relation and the query, and how to use them to derive bounds on the leakage and achieve the optimal utility
Fast convergence for consensus in dynamic networks

LNCS v. 3756 entitled: Automata, languages and programming : 38th international colloquium, ICALP 2011 ... proceedingsWe study the convergence time required to achieve consensus in dynamic networks. In each time step, a node's value is updated to some weighted average of its neighbors' and its old values. We study the case when the underlying network is dynamic, and investigate different averaging models. Both our analysis and experiments show that dynamic networks exhibit fast convergence behavior, even under very mild connectivity assumptions. © 2011 Springer-Verlag.postprin
Star forming dwarf galaxies

Star forming dwarf galaxies (SFDGs) have a high gas content and low
metallicities, reminiscent of the basic entities in hierarchical galaxy
formation scenarios. In the young universe they probably also played a major
role in the cosmic reionization. Their abundant presence in the local volume
and their youthful character make them ideal objects for detailed studies of
the initial stellar mass function (IMF), fundamental star formation processes
and its feedback to the interstellar medium. Occasionally we witness SFDGs
involved in extreme starbursts, giving rise to strongly elevated production of
super star clusters and global superwinds, mechanisms yet to be explored in
more detail. SFDGs is the initial state of all dwarf galaxies and the relation
to the environment provides us with a key to how different types of dwarf
galaxies are emerging. In this review we will put the emphasis on the exotic
starburst phase, as it seems less important for present day galaxy evolution
but perhaps fundamental in the initial phase of galaxy formation.Comment: To appear in JENAM Symposium "Dwarf Galaxies: Keys to Galaxy
  Formation and Evolution", P. Papaderos, G. Hensler, S. Recchi (eds.). Lisbon,
  September 2010, Springer Verlag, in pres
Physical properties of 6dF dwarf galaxies

Spectral synthesis is basically the decomposition of an observed spectrum in
terms of the superposition of a base of simple stellar populations of various
ages and metallicities, producing as output the star formation and chemical
histories of a galaxy, its extinction and velocity dispersion. The STARLIGHT
code provides one of the most powerful spectral synthesis tools presently
available. We have applied this code to the entire Six-Degree-Field Survey
(6dF) sample of nearby star-forming galaxies, selecting dwarf galaxy candidates
with the goal of: (1) deriving the age and metallicity of their stellar
populations and (2) creating a database with the physical properties of our
sample galaxies together with the FITS files of pure emission line spectra
(i.e. the observed spectra after subtraction of the best-fitting synthetic
stellar spectrum). Our results yield a good qualitative and quantitative
agreement with previous studies based on the Sloan Digital Sky Survey (SDSS).
However, an advantage of 6dF spectra is that they are taken within a twice as
large fiber aperture, much reducing aperture effects in studies of nearby dwarf
galaxies.Comment: To appear in JENAM Symposium "Dwarf Galaxies: Keys to Galaxy
  Formation and Evolution", P. Papaderos, S. Recchi, G. Hensler (eds.). Lisbon,
  September 2010, Springer Verlag, in pres
Unveiling the nature of the "Green Pea" galaxies

We review recent results on the oxygen and nitrogen chemical abundances in
extremely compact, low-mass starburst galaxies at redshifts between 0.1-0.3
recently named to as "Green Pea" galaxies. These galaxies are genuine
metal-poor galaxies ($\sim$ one fifth solar) with N/O ratios unusually high for
galaxies of the same metallicity. In combination with their known general
properties, i.e., size, stellar mass and star-formation rate, these findings
suggest that these objects could be experiencing a short and extreme phase in
their evolution. The possible action of both recent and massive inflow of gas,
as well as stellar feedback mechanisms are discussed here as main drivers of
the starburst activity and their oxygen and nitrogen abundances.Comment: To appear in JENAM Symposium "Dwarf Galaxies: Keys to Galaxy
  Formation and Evolution", P. Papaderos, G. Hensler, S. Recchi (eds.). Lisbon,
  September 2010, Springer Verlag, in pres
Predicting the frequencies of young and of tiny galaxies

A simple, 1-equation, galaxy formation model is applied to both the halo
merger tree derived from a high-resolution dissipationless cosmological
simulation and to 1/4 million Monte-Carlo halo merger trees. The galaxy
formation model involves a sharp entropy barrier against the accretion of gas
onto low-mass halos, the shock heating of infalling gas far from the central
regions of massive halos, and supernova feedback that drives the gas out of
shallow halo potential wells. With the first approach, we show that the large
majority of galaxies within group- and cluster-mass halos, known to be mainly
dwarf ellipticals, have acquired the bulk of their stellar mass through gas
accretion and not via galaxy mergers. With the second approach, we
qualitatively reproduce the downsizing trend of greater ages at greater masses
in stars and predict an upsizing trend of greater ages as one proceeds to
masses lower than 10^10 M_Sun. We find that the fraction of galaxies with very
young stellar populations (more than half the stellar mass formed within the
last 1.5 Gyr) is a function of present-day stellar mass, which peaks at 0.5% at
m_crit=10^7.5-9.5 M_Sun, roughly corresponding to the masses of blue compact
dwarfs. We predict that the stellar mass function of galaxies should not show a
maximum at m_stars > 10^{5.5}, M_Sun, with a power-law stellar mass function
with slope approx -1.6 if the IGM temperature in the outskirts of halos before
reionization is set by H2 cooling. We speculate on the nature of the lowest
mass galaxies.Comment: To appear in "Dwarf Galaxies: Keys to Galaxy Formation and Evolution"
  JENAM 2010 Symposium S3, eds. P. Papaderos, G. Hensler, S. Recch
Pairwise dwarf galaxy formation and galaxy downsizing: some clues from
  extremely metal-poor Blue Compact Dwarf galaxies

Some of the extremely metal-poor Blue Compact Dwarf galaxies (XBCDs) in the
nearby universe form galaxy pairs with remarkably similar properties. This fact
points to an intriguing degree of synchronicity in the formation history of
these binary dwarf galaxies and raises the question as to whether some of them
form and co-evolve pairwise (or in loose galaxy groups), experiencing recurrent
mild interactions and minor tidally induced star formation episodes throughout
their evolution. We argue that this hypothesis offers a promising conceptual
framework for the exploration of the retarded previous evolution and recent
dominant formation phase of XBCDs.Comment: To appear in the proceedings of the JENAM 2010 Symposium "Dwarf
  Galaxies: Keys to Galaxy Formation and Evolution" (Lisbon, 9-10 September
  2010), P. Papaderos, S. Recchi, G. Hensler (eds.), Springer Verlag (2011), in
  pres
A novel event-driven QoS-aware connection setup management scheme for optical networks

This paper proposes a QoS-Aware Optical Connection Setup Management scheme that uses the Earliest Deadline First (EDF) queueing discipline to schedule the setup of the optical connections. The benefits of this EDF-based scheme are twofold: a) it reduces the blocking probability since blocked connection requests due to resource unavailability are queued for possible future setup opportunities and b) it realizes QoS differentiation by ranking the blocked requests in the EDF queue according to their connection setup time requirements, which are viewed as deadlines during connection provisioning. As such, pending lesser delay-tolerant requests are guaranteed to experience better QoS than the ones having longer setup time requirements. Extensive simulations are performed to gauge the merits of the proposed EDF-based scheme and study its performance in the context of two network scenarios, namely, the National Science Foundation Network (NSFNET) and the European Optical Network (EON).N/
Towards A Collaborative Framework for Image Annotation and Search

This paper was presented at CAiSE 2011 International Workshops, London, UK, June 20-24, 2011 and published in the proceedings.Users tag images with plain text information, which is then used as the basis for search. For the large amount of digital images available on the web this becomes challenging because the tags are abstract concepts whose relationship is undefined. For effective search which requires reasoning on concepts and their relations one requires richer data structures for tagging and one needs to take into account the confidence and credibility of the tagging user. In this paper, we introduce a novel collaborative framework for image annotation, which allows users to create tags that are based on a concept repository which provides a hierarchical context for them as well as allowing to define relationships among said concepts. It also provides a new and systematic way to establish user credibility as well as to compute the truthfulness or reliability of a particular statement, which are used for ranking search results. A prototype has been implemented using this approach and we will show some examples to explain our methodology in detail.Peer-reviewedPost-prin
On stability of discretizations of the Helmholtz equation (extended
  version)

We review the stability properties of several discretizations of the
Helmholtz equation at large wavenumbers. For a model problem in a polygon, a
complete $k$-explicit stability (including $k$-explicit stability of the
continuous problem) and convergence theory for high order finite element
methods is developed. In particular, quasi-optimality is shown for a fixed
number of degrees of freedom per wavelength if the mesh size $h$ and the
approximation order $p$ are selected such that $kh/p$ is sufficiently small and
$p = O(\log k)$, and, additionally, appropriate mesh refinement is used near
the vertices. We also review the stability properties of two classes of
numerical schemes that use piecewise solutions of the homogeneous Helmholtz
equation, namely, Least Squares methods and Discontinuous Galerkin (DG)
methods. The latter includes the Ultra Weak Variational Formulation
A review on non iterative closed form configuration matching and rotations estimation

Orthonormal matrices, Procrustes and quaternion analysis are closed form solutions of the configuration matching problem, common in geodesy as in the datum transformation problem. Literature reports more Procrustes based geodetic applications than Quaternions, which are more used in other application fields, such as aerospace navigation, robotics and computer vision. The large popularity of Procrustes in geodesy is mainly due to its capability to take into account a priori observation weighting in a simple wa
Learning an atlas of a cognitive process in its functional geometry

In this paper we construct an atlas that captures functional characteristics of a cognitive process from a population of individuals. The functional connectivity is encoded in a low-dimensional embedding space derived from a diffusion process on a graph that represents correlations of fMRI time courses. The atlas is represented by a common prior distribution for the embedded fMRI signals of all subjects. The atlas is not directly coupled to the anatomical space, and can represent functional networks that are variable in their spatial distribution. We derive an algorithm for fitting this generative model to the observed data in a population. Our results in a language fMRI study demonstrate that the method identifies coherent and functionally equivalent regions across subjects.Proceedings of the 22nd International Conference, IPMI 2011, Kloster Irsee, Germany, July 3-8, 2011.National Science Foundation (U.S.) (IIS/CRCNS 0904625)National Science Foundation (U.S.) (CAREER grant 0642971)National Institutes of Health (U.S.) (NCRR NAC P41- RR13218)National Institute of Biomedical Imaging and Bioengineering (U.S.) (U54-EB005149)National Institutes of Health (U.S.) (U41RR019703)National Institutes of Health (U.S.) (P01CA067165)Seventh Framework Programme (European Commission) (n◦257528 (KHRESMOI)
A probabilistic framework to infer brain functional connectivity from anatomical connections

International audienceWe present a novel probabilistic framework to learn across several subjects a mapping from brain anatomical connectivity to functional connectivity, i.e. the covariance structure of brain activity. This prediction problem must be formulated as a structured-output learning task, as the predicted parameters are strongly correlated. We introduce a model selection framework based on cross-validation with a parametrization-independent loss function suitable to the manifold of covariance matrices. Our model is based on constraining the conditional independence structure of functional activity by the anatomical connectivity. Subsequently, we learn a linear predictor of a stationary multivariate autoregressive model. This natural parameterization of functional connectivity also enforces the positive-definiteness of the predicted covariance and thus matches the structure of the output space. Our results show that functional connectivity can be explained by anatomical connectivity on a rigorous statistical basis, and that a proper model of functional connectivity is essential to assess this link