3,350 research outputs found
Reductions of integrable equations on A.III-type symmetric spaces
We study a class of integrable non-linear differential equations related to
the A.III-type symmetric spaces. These spaces are realized as factor groups of
the form SU(N)/S(U(N-k) x U(k)). We use the Cartan involution corresponding to
this symmetric space as an element of the reduction group and restrict generic
Lax operators to this symmetric space. The symmetries of the Lax operator are
inherited by the fundamental analytic solutions and give a characterization of
the corresponding Riemann-Hilbert data.Comment: 14 pages, 1 figure, LaTeX iopart styl
Nonequilibrium pattern formation in chiral Langmuir monolayers with transmembrane flows
Nonequilibrium Langmuir monolayers including a fraction of chiral molecules
and subject to transmembrane flow are considered. The flow induces coherent
collective precession of chiral molecules. Our theoretical study shows that
splay interactions in this system lead to spatial redistribution of chiral
molecules and formation of spiral waves and target patterns observed in
experiments
From Development To Evolution: The Re-Establishment Of The Alexander Kowalevsky Medal
The Saint Petersburg Society of Naturalists has reinstated the Alexander O. Kowalevsky Medal. This article announces the winners of the first medals and briefly reviews the achievements of A.O. Kowalevsky,the Russian comparative embryologist whose studies on amphioxus, tunicates and germ layer homologies pioneered evolutionary embryology and confirmed the evolutionary continuity between invertebrates and vertebrates. In re-establishing this international award, the Society is pleased to recognize both the present awardees and the memory of Kowalevsky, whose work pointed to that we now call evolutionary developmental biology
Dynamical clustering in oscillator ensembles with time-dependent interactions
We consider an ensemble of coupled oscillators whose individual states, in
addition to the phase, are characterized by an internal variable with
autonomous evolution. The time scale of this evolution is different for each
oscillator, so that the ensemble is inhomogeneous with respect to the internal
variable. Interactions between oscillators depend on this variable and thus
vary with time. We show that as the inhomogeneity of time scales in the
internal evolution grows, the system undergoes a critical transition between
ordered and incoherent states. This transition is mediated by a regime of
dynamical clustering, where the ensemble recurrently splits into groups formed
by varying subpopulations.Comment: 4 pages, 3 figure
Ridges and Soft Jet Components in Untriggered Di-hadron Correlations in Pb+Pb Collisions at 2.76 TeV
We study untriggered di-hadron correlations in Pb+Pb at 2.76 TeV, based on an
event-by-event simulation of a hydrodynamic expansion starting from flux tube
initial conditions. The correlation function shows interesting structures as a
function of the pseudorapidity difference and the azimuthal angle
difference , in particular comparing different centralities. We can
clearly identify a peak-like nearside structure associated with very low
momentum components of jets for peripheral collisions, which disappears towards
central collisions. On the other hand, a very broad ridge structure from
asymmetric flow seen at central collisions, gets smaller and finally disappears
towards peripheral collisions
Bose-Einstein Correlations in a Fluid Dynamical Scenario for Proton-Proton Scattering at 7 TeV
Using a fluid dynamical scenario for scattering at 7 TeV, we compute
correlation functions for pairs. Femtoscopic radii are extracted
based on three-dimensional parametrizations of the correlation functions. We
study the radii as a function of the transverse momenta of the pairs, for
different multiplicity classes, corresponding to recent experimental results
from ALICE. We find the same decrease of the radii with , more and more
pronounced with increasing multiplicity, but absent for the lowest
multiplicities. In the model we understand this as transition from string
expansion (low multiplicity) towards a three-dimensional hydrodynamical
expansion (high multiplicity)
Analysis of some localized boundary-domain integral equations for transmission problems with variable coefficients
This is the post-print version of the Article. The official published version can be found at the links below - Copyright @ 2011 Birkhäuser Boston.Some segregated systems of direct localized boundary-domain integral equations (LBDIEs) associated with several transmission problems for scalar PDEs with variable coefficients are formulated and analyzed for a bounded domain composed of two subdomains with a coefficient jump over the interface. The main results established in the paper are the LBDIE equivalence to the original transmission problems and the invertibility of the corresponding localized boundary-domain integral operators in corresponding Sobolev spaces function spaces.This research was supported by the EPSRC grant EP/H020497/1: ”Mathematical analysis of Localized Boundary-Domain Integral
Equations for Variable-Coefficient Boundary Value Problems” and partly by the Georgian Technical University grant in the case of the third author
Numerics of boundary-domain integral and integro-differential equations for BVP with variable coefficient in 3D
This is the post-print version of the article. The official published version can be accessed from the links below - Copyright @ 2013 Springer-VerlagA numerical implementation of the direct boundary-domain integral and integro-differential equations, BDIDEs, for treatment of the Dirichlet problem for a scalar elliptic PDE with variable coefficient in a three-dimensional domain is discussed. The mesh-based discretisation of the BDIEs with tetrahedron domain elements in conjunction with collocation method leads to a system of linear algebraic equations (discretised BDIE). The involved fully populated matrices are approximated by means of the H-Matrix/adaptive cross approximation technique. Convergence of the method is investigated.This study is partially supported by the EPSRC grant EP/H020497/1:"Mathematical Analysis of Localised-Boundary-Domain Integral Equations for Variable-Coefficients
Boundary Value Problems"
Inter-valley plasmons in graphene
The spectrum of two-dimensional (2D) plasma waves in graphene has been
recently studied in the Dirac fermion model. We take into account the whole
dispersion relation for graphene electrons in the tight binding approximation
and the local field effects in the electrodynamic response. Near the
wavevectors close to the corners of the hexagon-shaped Brillouin zone we found
new low-frequency 2D plasmon modes with a linear spectrum. These "inter-valley"
plasmon modes are related to the transitions between the two nearest Dirac
cones.Comment: 4 pages, 2 figures; submitted in PR
Russian comparative embryology takes form: a conceptual metamorphosis toward “evo-devo”
[Abstract] This essay recapitulates major paths followed by the Russian tradition of what we refer to today as evolutionary developmental biology (“evo-devo”). The article addresses several questions regarding the conceptual history of evolutionary embryological thought in its particularly Russian perspective: (1) the assertion by the St. Petersburg academician Wolff regarding the possible connections between environmental modifications during morphogenesis and the “transformation” of species, (2) the discovery of shared “principles” underlying animal development by von Baer, (3) the experimental expression of Baer's principles by Kowalevsky and Mechnikoff, (4) Severtsov's theory of phylembryogenesis, (5) Filatov's approach to the study of evolution using comparative “developmental mechanics”, and (6) Shmalgausen's concept of “stabilizing” selection as an attempt to elucidate the evolution of developmental mechanisms. The focus on comparative evolutionary embryology, which was established by Kowalevsky and Mechnikoff, still continues to be popular in present-day “evo-devo” research in Russia.Ministerio de Ciencia e Innovación; SAF2008-00337Galicia. Consellería de Economía e Industria; 08CSA008161P
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