5,683 research outputs found
Near-optimal small-depth lower bounds for small distance connectivity
We show that any depth- circuit for determining whether an -node graph
has an -to- path of length at most must have size
. The previous best circuit size lower bounds for this
problem were (due to Beame, Impagliazzo, and Pitassi
[BIP98]) and (following from a recent formula size
lower bound of Rossman [Ros14]). Our lower bound is quite close to optimal,
since a simple construction gives depth- circuits of size
for this problem (and strengthening our bound even to
would require proving that undirected connectivity is not in )
Our proof is by reduction to a new lower bound on the size of small-depth
circuits computing a skewed variant of the "Sipser functions" that have played
an important role in classical circuit lower bounds [Sip83, Yao85, H{\aa}s86].
A key ingredient in our proof of the required lower bound for these Sipser-like
functions is the use of \emph{random projections}, an extension of random
restrictions which were recently employed in [RST15]. Random projections allow
us to obtain sharper quantitative bounds while employing simpler arguments,
both conceptually and technically, than in the previous works [Ajt89, BPU92,
BIP98, Ros14]
Comments: Eminent Domain: Private Corporations and the Public Use Limitation
Though no logical limits are evident in the cases, it nonetheless remains to be seen how far courts will be willing to go in allowing local development authorities to condemn property for commercial purposes
Linear Toric Fibrations
These notes are based on three lectures given at the 2013 CIME/CIRM summer
school. The purpose of this series of lectures is to introduce the notion of a
toric fibration and to give its geometrical and combinatorial
characterizations. Polarized toric varieties which are birationally equivalent
to projective toric bundles are associated to a class of polytopes called
Cayley polytopes. Their geometry and combinatorics have a fruitful interplay
leading to fundamental insight in both directions. These notes will illustrate
geometrical phenomena, in algebraic geometry and neighboring fields, which are
characterized by a Cayley structure. Examples are projective duality of toric
varieties and polyhedral adjunction theory
Helicobacter pylori infection and gastric dysbiosis: Can probiotics administration be useful to treat this condition?
Helicobacter pylori (Hp) is responsible for one of the most common infections in the world. 'e prevalence exceeds 50% of the
population in developing countries, and approximately one-third of the adults are colonized in North Europe and North America.
It is considered a major pathogenic agent of chronic gastritis, peptic ulcer, atrophic gastritis, gastric cancer, and mucosa-associated
lymphoid tissue lymphoma (MALT). Hp colonization modifies the composition of gastric microbiota that could drive the
development of gastric disorders. Currently, an emerging problem in Hp treatment is represented by the increasing rate of
antimicrobial therapy resistance. In this context, the search for adjuvant agents can be very useful to overcome this issue and
probiotics administration can represent a valid option. The aim of this review is to describe the gastric microbiota changes during
Hp colonization, the mechanisms of action, and a possible role of probiotics in the treatment of this infection
A data summary file structure and analysis tools for neutrino oscillation analysis at the NOνA experiment
The NuMI Off-axis Neutrino Experiment (NOvA) is designed to study neutrino oscillations in the NuMI beam at Fermilab. Neutrinos at the Main Injector (NuMI) is currently being upgraded to provide 700 kW for NOvA. A 14 kt Far Detector in Ash River, MN and a functionally identical 0.3 kt Near Detector at Fermilab are positioned 810 km apart in the NuMI beam line. The fine granularity of the NOvA detectors provides a detailed representation of particle trajectories. The data volume associated with such granularity, however, poses problems for analyzing data with ease and speed. NOvA has developed a data summary file structure which discards the full event record in favor of higher-level reconstructed information. A general- purpose framework for neutrino oscillation measurements has been developed for analysis of these data summary files. We present the design methodology for this new file format as well as the analysis framework and the role it plays in producing NOvA physics results
Inclusive electron-nucleus cross section within the Self Consistent Green's Function approach
We compute inclusive electron-nucleus cross sections using ab initio spectral
functions of He and O obtained within the Self Consistent Green's
Function approach. The formalism adopted is based on the factorization of the
spectral function and the nuclear transition matrix elements. This allows to
provide an accurate description of nuclear dynamics and to account for
relativistic effects in the interaction vertex. Our calculations use a
saturating chiral Hamiltonian in order reproduce the correct nuclear sizes.
When final state interactions for the struck particle are accounted for, we
find nice agreement between the data and the theory for the inclusive
electron-O cross section. The results lay the foundations for future
applications of the Self Consistent Green's Function method, in both closed and
open shell nuclei, to neutrino data analysis.
This work also presents results for the point-proton, charge and
single-nucleon momentum distribution of the same two nuclei. The center of mass
can affect these quantities for light nuclei and cannot be separated cleanly in
most ab initio post-Hartree-Fock methods. In order to address this, we
developed a Metropolis Monte Carlo calculation in which the center of mass
coordinate can be subtracted exactly from the trial wave function and the
expectation values. We gauged this effect for He by removing the center of
mass effect from the Optimal Reference State wave function that is generated
during the Self Consistent Green's Function calculations. Our findings clearly
indicate that the residual center of mass contribution strongly modifies
calculated matter distributions with respect to those obtained in the intrinsic
frame. Hence, its subtraction is crucial for a correct description of light
nuclei.Comment: 12 pages, 10 figure
Learning circuits with few negations
Monotone Boolean functions, and the monotone Boolean circuits that compute
them, have been intensively studied in complexity theory. In this paper we
study the structure of Boolean functions in terms of the minimum number of
negations in any circuit computing them, a complexity measure that interpolates
between monotone functions and the class of all functions. We study this
generalization of monotonicity from the vantage point of learning theory,
giving near-matching upper and lower bounds on the uniform-distribution
learnability of circuits in terms of the number of negations they contain. Our
upper bounds are based on a new structural characterization of negation-limited
circuits that extends a classical result of A. A. Markov. Our lower bounds,
which employ Fourier-analytic tools from hardness amplification, give new
results even for circuits with no negations (i.e. monotone functions)
Ab initio calculation of the electromagnetic and neutral-weak response functions of 4He and 12C
Precise measurement of neutrino oscillations, and hence the determination of
their masses demands a quantitative understanding of neutrino-nucleus
interactions. To this aim, two-body meson-exchange currents have to be
accounted for along within realistic models of nuclear dynamics. We summarize
our progresses towards the construction of a consistent framework, based on
quantum Monte Carlo methods and on the spectral function approach, that can be
exploited to accurately describe neutrino interactions with atomic nuclei over
the broad kinematical region covered by neutrino experiments.Comment: 8 pages, 4 figure, Proceedings of the 21st International Conference
on Few-Body Problems in Physics, Chicago, Illinois, US
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