130 research outputs found
Three-algebra for supermembrane and two-algebra for superstring
While string or Yang-Mills theories are based on Lie algebra or two-algebra
structure, recent studies indicate that M-theory may require a one higher,
three-algebra structure. Here we construct a covariant action for a
supermembrane in eleven dimensions, which is invariant under global
supersymmetry, local fermionic symmetry and worldvolume diffeomorphism. Our
action is classically on-shell equivalent to the celebrated
Bergshoeff-Sezgin-Townsend action. However, the novelty is that we spell the
action genuinely in terms of Nambu three-brackets: All the derivatives appear
through Nambu brackets and hence it manifests the three-algebra structure.
Further the double dimensional reduction of our action gives straightforwardly
to a type IIA string action featuring two-algebra. Applying the same method, we
also construct a covariant action for type IIB superstring, leading directly to
the IKKT matrix model.Comment: 1+15 pages, no figure; Refs added, Accepted for publication in JHE
The effective bandwidth problem revisited
The paper studies a single-server queueing system with autonomous service and
priority classes. Arrival and departure processes are governed by marked
point processes. There are buffers corresponding to priority classes,
and upon arrival a unit of the th priority class occupies a place in the
th buffer. Let , denote the quota for the total
th buffer content. The values are assumed to be large, and
queueing systems both with finite and infinite buffers are studied. In the case
of a system with finite buffers, the values characterize buffer
capacities.
The paper discusses a circle of problems related to optimization of
performance measures associated with overflowing the quota of buffer contents
in particular buffers models. Our approach to this problem is new, and the
presentation of our results is simple and clear for real applications.Comment: 29 pages, 11pt, Final version, that will be published as is in
Stochastic Model
Absorption and scattering properties of arbitrarily shaped particles in the Rayleigh domain: A rapid computational method and a theoretical foundation for the statistical approach
We provide a theoretical foundation for the statistical approach for
computing the absorption properties of particles in the Rayleigh domain. We
present a general method based on the Discrete Dipole Approximation (DDA) to
compute the absorption and scattering properties of particles in the Rayleigh
domain. The method allows to separate the geometrical aspects of a particle
from its material properties. Doing the computation of the optical properties
of a particle once, provides them for any set of refractive indices,
wavelengths and orientations. This allows for fast computations of e.g.
absorption spectra of arbitrarily shaped particles. Other practical
applications of the method are in the interpretation of atmospheric and radar
measurements as well as computations of the scattering matrix of small
particles as a function of the scattering angle. In the statistical approach,
the optical properties of irregularly shaped particles are represented by the
average properties of an ensemble of particles with simple shapes. We show that
the absorption cross section of an ensemble of arbitrarily shaped particles
with arbitrary orientations can always be uniquely represented by the average
absorption cross section of an ensemble of spheroidal particles with the same
composition and fixed orientation. This proves for the first time that the
statistical approach is generally viable in the Rayleigh domain.Comment: Accepted for publication in JQSR
Study of KS KL Coupled Decays and KL -Be Interactions with the CMD-2 Detector at VEPP-2M Collider
The integrated luminosity about 4000 inverse nanobarn of around phi meson
mass ( 5 millions of phi mesons) has been collected with the CMD-2 detector at
the VEPP-2M collider. A latest analysis of the KS KL coupled decays based on 30
% of available data is presented in this paper.
The KS KL pairs from phi meson decays were reconstructed in the drift chamber
when both kaons decayed into two charged particles. From a sample of 1423
coupled decays a selection of candidates to the CP violating KL into pi+ pi-
decay was performed. CP violating decays were not identified because of the
domination of events with a KL regenerating at the Be beam pipe into KS and a
background from KL semileptonic decays.
The regeneration cross section of 110 MeV/c KL mesons was found to be 53 +-
17 mb in agreement with theoretical expectations. The angular distribution of
KS mesons after regeneration and the total cross section of KL for Be have been
measured.Comment: 14 pages, 8 figure
Metric 3-Lie algebras for unitary Bagger-Lambert theories
We prove a structure theorem for finite-dimensional indefinite-signature
metric 3-Lie algebras admitting a maximally isotropic centre. This algebraic
condition indicates that all the negative-norm states in the associated
Bagger-Lambert theory can be consistently decoupled from the physical Hilbert
space. As an immediate application of the theorem, new examples beyond index 2
are constructed. The lagrangian for the Bagger-Lambert theory based on a
general physically admissible 3-Lie algebra of this kind is obtained. Following
an expansion around a suitable vacuum, the precise relationship between such
theories and certain more conventional maximally supersymmetric gauge theories
is found. These typically involve particular combinations of N=8 super
Yang-Mills and massive vector supermultiplets. A dictionary between the 3-Lie
algebraic data and the physical parameters in the resulting gauge theories will
thereby be provided.Comment: 38 page
Limit cycles in uniform isochronous centers of discontinuous differential systems with four zones
We apply the averaging theory of first order for discontinuous differential systems to study the bifurcation of limit cycles from the periodic orbits of the uniform isochronous center of the differential systems áș = -y+x, y = x + xy, and áș = -y + xy, y = x + xy, when they are perturbed inside the class of all discontinuous quadratic and cubic polynomials differential systems with four zones separately by the axes of coordinates, respectively. Using averaging theory of first order the maximum number of limit cycles that we can obtain is twice the maximum number of limit cycles obtained in a previous work for discontinuous quadratic differential systems perturbing the same uniform isochronous quadratic center at origin perturbed with two zones separately by a straight line, and 5 more limit cycles than those achieved in a prior result for discontinuous cubic differential systems with the same uniform isochronous cubic center at the origin perturbed with two zones separately by a straight line. Comparing our results with those obtained perturbing the mentioned centers by the continuous quadratic and cubic differential systems we obtain 8 and 9 more limit cycles respectively
The Origin, Early Evolution and Predictability of Solar Eruptions
Coronal mass ejections (CMEs) were discovered in the early 1970s when space-borne coronagraphs revealed that eruptions of plasma are ejected from the Sun. Today, it is known that the Sun produces eruptive flares, filament eruptions, coronal mass ejections and failed eruptions; all thought to be due to a release of energy stored in the coronal magnetic field during its drastic reconfiguration. This review discusses the observations and physical mechanisms behind this eruptive activity, with a view to making an assessment of the current capability of forecasting these events for space weather risk and impact mitigation. Whilst a wealth of observations exist, and detailed models have been developed, there still exists a need to draw these approaches together. In particular more realistic models are encouraged in order to asses the full range of complexity of the solar atmosphere and the criteria for which an eruption is formed. From the observational side, a more detailed understanding of the role of photospheric flows and reconnection is needed in order to identify the evolutionary path that ultimately means a magnetic structure will erupt
Measurement of CP asymmetries and branching fraction ratios of Bâ decays to two charm mesons
The asymmetries of seven decays to two charm mesons are measured using data corresponding to an integrated luminosity of of proton-proton collisions collected by the LHCb experiment. Decays involving a or meson are analysed by reconstructing only the or decay products. This paper presents the first measurement of and , and the most precise measurement of the other five asymmetries. There is no evidence of violation in any of the analysed decays. Additionally, two ratios between branching fractions of selected decays are measured.The CP asymmetries of seven B decays to two charm mesons are measured using data corresponding to an integrated luminosity of 9 fb of proton-proton collisions collected by the LHCb experiment. Decays involving a D or meson are analysed by reconstructing only the D or decay products. This paper presents the first measurement of (BâD) and (BâD), and the most precise measurement of the other five CP asymmetries. There is no evidence of CP violation in any of the analysed decays. Additionally, two ratios between branching fractions of selected decays are measured.[graphic not available: see fulltext]The asymmetries of seven decays to two charm mesons are measured using data corresponding to an integrated luminosity of of proton-proton collisions collected by the LHCb experiment. Decays involving a or meson are analysed by reconstructing only the or decay products. This paper presents the first measurement of and , and the most precise measurement of the other five asymmetries. There is no evidence of violation in any of the analysed decays. Additionally, two ratios between branching fractions of selected decays are measured
Helium identification with LHCb
The identification of helium nuclei at LHCb is achieved using a method based on measurements of ionisation losses in the silicon sensors and timing measurements in the Outer Tracker drift tubes. The background from photon conversions is reduced using the RICH detectors and an isolation requirement. The method is developed using pp collision data at â(s) = 13 TeV recorded by the LHCb experiment in the years 2016 to 2018, corresponding to an integrated luminosity of 5.5 fb-1. A total of around 105 helium and antihelium candidates are identified with negligible background contamination. The helium identification efficiency is estimated to be approximately 50% with a corresponding background rejection rate of up to O(10^12). These results demonstrate the feasibility of a rich programme of measurements of QCD and astrophysics interest involving light nuclei
Curvature-bias corrections using a pseudomass method
Momentum measurements for very high momentum charged particles, such as muons from electroweak vector boson decays, are particularly susceptible to charge-dependent curvature biases that arise from misalignments of tracking detectors. Low momentum charged particles used in alignment procedures have limited sensitivity to coherent displacements of such detectors, and therefore are unable to fully constrain these misalignments to the precision necessary for studies of electroweak physics. Additional approaches are therefore required to understand and correct for these effects. In this paper the curvature biases present at the LHCb detector are studied using the pseudomass method in proton-proton collision data recorded at centre of mass energy â(s)=13 TeV during 2016, 2017 and 2018. The biases are determined using ZâÎŒ + ÎŒ - decays in intervals defined by the data-taking period, magnet polarity and muon direction. Correcting for these biases, which are typically at the 10-4 GeV-1 level, improves the ZâÎŒ + ÎŒ - mass resolution by roughly 18% and eliminates several pathological trends in the kinematic-dependence of the mean dimuon invariant mass
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