2,450 research outputs found
Towards Field Theory in Spaces with Multivolume Junctions
We consider a spacetime formed by several pieces having common timelike
boundary which plays the role of a junction between them. We establish junction
conditions for fields of various spin and derive the resulting laws of wave
propagation through the junction, which turn out to be quite similar for fields
of all spins. As an application, we consider the case of multivolume junctions
in four-dimensional spacetime that may arise in the context of the theory of
quantum creation of a closed universe on the background of a big mother
universe. The theory developed can also be applied to braneworld models and to
the superstring theory.Comment: 20 pages, 3 figures, revtex; published versio
Конструктивные решения несъемной железобетонной опалубки для комплексного повышения эксплуатационных качеств гражданских зданий
The objective of this article is to analyze and propose ways of improving unskimed reinforced formwork being a forming unit of civic building performance. The authors propose integrated design concepts to wall unskimed reinforced forms ensuring integrated improvement of framework performance.В данной работе объектом анализа и совершенствования являются конструктивные решения несъемной железобетонной стеновой опалубки как элемента, формирующего систему эксплуатационных качеств (ЭК) каркаса гражданского здания. Предложен комплекс конструктивных решений несъемной железобетонной стеновой опалубки, обеспечивающих комплексное повышение ЭК каркаса
Applications of BGP-reflection functors: isomorphisms of cluster algebras
Given a symmetrizable generalized Cartan matrix , for any index , one
can define an automorphism associated with of the field of rational functions of independent indeterminates It is an isomorphism between two cluster algebras associated to the
matrix (see section 4 for precise meaning). When is of finite type,
these isomorphisms behave nicely, they are compatible with the BGP-reflection
functors of cluster categories defined in [Z1, Z2] if we identify the
indecomposable objects in the categories with cluster variables of the
corresponding cluster algebras, and they are also compatible with the
"truncated simple reflections" defined in [FZ2, FZ3]. Using the construction of
preprojective or preinjective modules of hereditary algebras by Dlab-Ringel
[DR] and the Coxeter automorphisms (i.e., a product of these isomorphisms), we
construct infinitely many cluster variables for cluster algebras of infinite
type and all cluster variables for finite types.Comment: revised versio
A New World Average Value for the Neutron Lifetime
The analysis of the data on measurements of the neutron lifetime is
presented. A new most accurate result of the measurement of neutron lifetime
[Phys. Lett. B 605 (2005) 72] 878.5 +/- 0.8 s differs from the world average
value [Phys. Lett. B 667 (2008) 1] 885.7 +/- 0.8 s by 6.5 standard deviations.
In this connection the analysis and Monte Carlo simulation of experiments
[Phys. Lett. B 483 (2000) 15] and [Phys. Rev. Lett. 63 (1989) 593] is carried
out. Systematic errors of about -6 s are found in each of the experiments. The
summary table for the neutron lifetime measurements after corrections and
additions is given. A new world average value for the neutron lifetime 879.9
+/- 0.9 s is presented.Comment: 27 pages, 13 figures; Fig.13 update
Hadronic unquenching effects in the quark propagator
We investigate hadronic unquenching effects in light quarks and mesons.
Within the non-perturbative continuum framework of Schwinger-Dyson and
Bethe-Salpeter equations we quantify the strength of the back reaction of the
pion onto the quark-gluon interaction. To this end we add a Yang-Mills part of
the interaction such that unquenched lattice results for various current quark
masses are reproduced. We find considerable effects in the quark mass function
at low momenta as well as for the chiral condensate. The quark wave function is
less affected. The Gell--Mann-Oakes-Renner relation is valid to good accuracy
up to pion masses of 400-500 MeV. As a byproduct of our investigation we verify
the Coleman theorem, that chiral symmetry cannot be broken spontaneously when
QCD is reduced to 1+1 dimensions.Comment: 27 pages, 15 figures, minor corrections and clarifications; version
to appear in PR
Magnetic field driven instability of charged center in graphene
It is shown that a magnetic field dramatically affects the problem of
supercritical charge in graphene making any charge in gapless theory
supercritical. The cases of radially symmetric potential well and Coulomb
center in an homogeneous magnetic field are considered. The local density of
states and polarization charge density are calculated in the first order of
perturbation theory. It is argued that the magnetically induced instability of
the supercritical Coulomb center can be considered as a quantum mechanical
counterpart of the magnetic catalysis phenomenon in graphene.Comment: 10 pages, 4 figures; to be published in PR
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