414 research outputs found
Hamiltonian dynamics and spectral theory for spin-oscillators
We study the Hamiltonian dynamics and spectral theory of spin-oscillators.
Because of their rich structure, spin-oscillators display fairly general
properties of integrable systems with two degrees of freedom. Spin-oscillators
have infinitely many transversally elliptic singularities, exactly one
elliptic-elliptic singularity and one focus-focus singularity. The most
interesting dynamical features of integrable systems, and in particular of
spin-oscillators, are encoded in their singularities. In the first part of the
paper we study the symplectic dynamics around the focus-focus singularity. In
the second part of the paper we quantize the coupled spin-oscillators systems
and study their spectral theory. The paper combines techniques from
semiclassical analysis with differential geometric methods.Comment: 32 page
Un nuevo concepto de la gastronomía desde la bioeconomía y la actividad académica
El proyecto “Ciencia y arte en gastronomía: botánica gastronómica y
gastronomía molecular” se está desarrollando con el objetivo de establecer y
organizar el intercambio de conocimientos y negocio en este ámbito. Con este
objetivo se pretende aunar el conocimiento científico con la salud y el bienestar
social desde la perspectiva bioeconómica promoviendo la creación de riqueza y
trabajo. El proyecto forma parte de los cursos especializados que la Universidad
Complutense de Madrid oferta con el animo de incrementar el conocimiento y
desarrollar competencias personales y profesionales. El programa responde a la
demanda social proporcionando una formación con inmediata proyección
profesional mediante el establecimiento de un nexo directo entre la actividad
académica y la realidad social.Universidad de Sevilla. Cristalografía, Mineralogía y Química Agrícola
The project "Science and art in gastronomy: gastronomic botany and
molecular gastronomy" is being developed with the aim to establish and organize
the exchange of knowledge and business in this area. In this way we are working
to join the scientific knowledge to the health and the social well-being, without
losing the current perspective from the bioeconomy which look forward the generation of wealth and work. The project belongs to specialized courses
offered by The Complutense University of Madrid which aim is to update the
knowledge and develop personal and professional competitions. These programs
answer to a social demand on providing formation with professional immediate
projection establishing a direct relation between the academic activity and the
social reality
Observer dependence for the phonon content of the sound field living on the effective curved space-time background of a Bose-Einstein condensate
We demonstrate that the ambiguity of the particle content for quantum fields
in a generally curved space-time can be experimentally investigated in an
ultracold gas of atoms forming a Bose-Einstein condensate. We explicitly
evaluate the response of a suitable condensed matter detector, an ``Atomic
Quantum Dot,'' which can be tuned to measure time intervals associated to
different effective acoustic space-times. It is found that the detector
response related to laboratory, ``adiabatic,'' and de Sitter time intervals is
finite in time and nonstationary, vanishing, and thermal, respectively.Comment: 9 pages, 2 figures; references updated, as published in Physical
Review
Effective Field Theories on Non-Commutative Space-Time
We consider Yang-Mills theories formulated on a non-commutative space-time
described by a space-time dependent anti-symmetric field .
Using Seiberg-Witten map techniques we derive the leading order operators for
the effective field theories that take into account the effects of such a
background field. These effective theories are valid for a weakly
non-commutative space-time. It is remarkable to note that already simple models
for can help to loosen the bounds on space-time
non-commutativity coming from low energy physics. Non-commutative geometry
formulated in our framework is a potential candidate for new physics beyond the
standard model.Comment: 22 pages, 1 figur
On Slow Light as a Black Hole Analogue
Although slow light (electromagnetically induced transparency) would seem an
ideal medium in which to institute a ``dumb hole'' (black hole analog), it
suffers from a number of problems. We show that the high phase velocity in the
slow light regime ensures that the system cannot be used as an analog
displaying Hawking radiation. Even though an appropriately designed slow-light
set-up may simulate classical features of black holes -- such as horizon, mode
mixing, Bogoliubov coefficients, etc. -- it does not reproduce the related
quantum effects. PACS: 04.70.Dy, 04.80.-y, 42.50.Gy, 04.60.-m.Comment: 14 pages RevTeX, 5 figure
Persistent currents in a circular array of Bose-Einstein condensates
A ring-shaped array of Bose-Einstein condensed atomic gases can display
circular currents if the relative phase of neighboring condensates becomes
locked to certain values. It is shown that, irrespective of the mechanism
responsible for generating these states, only a restricted set of currents are
stable, depending on the number of condensates, on the interaction and
tunneling energies, and on the total number of particles. Different
instabilities due to quasiparticle excitations are characterized and possible
experimental setups for testing the stability prediction are also discussed.Comment: 7 pages, REVTex
On the selection of AGN neutrino source candidates for a source stacking analysis with neutrino telescopes
The sensitivity of a search for sources of TeV neutrinos can be improved by
grouping potential sources together into generic classes in a procedure that is
known as source stacking. In this paper, we define catalogs of Active Galactic
Nuclei (AGN) and use them to perform a source stacking analysis. The grouping
of AGN into classes is done in two steps: first, AGN classes are defined, then,
sources to be stacked are selected assuming that a potential neutrino flux is
linearly correlated with the photon luminosity in a certain energy band (radio,
IR, optical, keV, GeV, TeV). Lacking any secure detailed knowledge on neutrino
production in AGN, this correlation is motivated by hadronic AGN models, as
briefly reviewed in this paper.
The source stacking search for neutrinos from generic AGN classes is
illustrated using the data collected by the AMANDA-II high energy neutrino
detector during the year 2000. No significant excess for any of the suggested
groups was found.Comment: 43 pages, 12 figures, accepted by Astroparticle Physic
Test beam performance measurements for the Phase I upgrade of the CMS pixel detector
A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. In this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency is (99.95 ± 0.05) %, while the intrinsic spatial resolutions are (4.80 ± 0.25) μm and (7.99 ± 0.21) μm along the 100 μm and 150 μm pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.Peer reviewe
Measurement of the View the tt production cross-section using eμ events with b-tagged jets in pp collisions at √s = 13 TeV with the ATLAS detector
This paper describes a measurement of the inclusive top quark pair production cross-section (σtt¯) with a data sample of 3.2 fb−1 of proton–proton collisions at a centre-of-mass energy of √s = 13 TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electron–muon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously σtt¯ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be:
σtt¯ = 818 ± 8 (stat) ± 27 (syst) ± 19 (lumi) ± 12 (beam) pb,
where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented
Search for strong gravity in multijet final states produced in pp collisions at √s=13 TeV using the ATLAS detector at the LHC
A search is conducted for new physics in multijet final states using 3.6 inverse femtobarns of data from proton-proton collisions at √s = 13TeV taken at the CERN Large Hadron Collider with the ATLAS detector. Events are selected containing at least three jets with scalar sum of jet transverse momenta (HT) greater than 1TeV. No excess is seen at large HT and limits are presented on new physics: models which produce final states containing at least three jets and having cross sections larger than 1.6 fb with HT > 5.8 TeV are excluded. Limits are also given in terms of new physics models of strong gravity that hypothesize additional space-time dimensions
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