2,508 research outputs found
Continuation of Direct Products of Distributions
If, in some problems, one has to deal with the ``product'' of distributions
(also called generalized functions) ,
this product has a priori no definite meaning as a functional for . But if exists,
whatever the associativity is between some powers of () and the various , then a continuation of the linear functional from
onto for some is shown to exist in such a way that is defined unambiguously, and , significant, though not unique.Comment: 3 pages, late
On the Four-Color-Map Theorem
Coloring planar Feynman diagrams in spinor quantum electrodynamics, is a non
trivial model soluble without computer. Four colors are necessary and
sufficient.Comment: 8 page
A search for exact superstring vacua
We investigate sigma-models with a dimensional Minkowski signature
target space metric and Killing symmetry, specifically supersymmetrized, and
see under which conditions they might lead to corresponding exact string vacua.
It appears that the issue relies heavily on the properties of the vector
, a reparametrization term, which needs to possess a definite form for
the Weyl invariance to be satisfied. We give, in the supersymmetric
case, two non-renormalization theorems from which we can relate the
component of to the function. We work out this
component of the function and find a non-vanishing contribution at
four loops. Therefore, it turns out that at order , there
are in general non-vanishing contributions to that prevent us from
deducing superstring vacua in closed form.Comment: 9 pages, latex, CERN-TH.6946/9
Explicit supertring vacua in a background of gravitational waves and dilaton
We present an explicit solution of superstring effective equations,
represented by gravitational waves and dilaton backgrounds. Particular
solutions will be examined in a forthcoming note.Comment: 10 pages, latex, CERN-TH.7373/9
Precise mass-dependent QED contributions to leptonic g-2 at order alpha^2 and alpha^3
Improved values for the two- and three-loop mass-dependent QED contributions
to the anomalous magnetic moments of the electron, muon, and tau lepton are
presented. The Standard Model prediction for the electron (g-2) is compared
with its most precise recent measurement, providing a value of the
fine-structure constant in agreement with a recently published determination.
For the tau lepton, differences with previously published results are found and
discussed. An updated value of the fine-structure constant is presented in
"Note added after publication."Comment: 6 pages, 1 figure. v2: New determination of alpha presented (based on
the recent electron g-2 measurement). v3: New formulae added in Sec.IIB. v4:
Updated value of alpha presente
Analytical eighth-order light-by-light QED contributions from leptons with heavier masses to the anomalous magnetic moment of electron
The important consequences of the recent results of the numerical evaluations
of eighth and tenth order QED contributions to the anomalous magnetic moment of
electron are commented. The correctness of the results of the numerical
evaluation of new eighth order QED corrections to the electron anomaly are
supported by the demonstration of their consistency with the new analytical
expressions for the QED contributions to from the diagrams with
fourth-order light-by-light scattering muon and tau-lepton loops. The
consistency of the similar results are demonstrated in the case of eighth order
massive dependent contribution to the muon anomalous magnetic moment.Comment: 6 pages, LaTeX, The preliminary version of the longer work with the
same title was registered as CERN Preprint during the visit to Theory
Division of CERN in January of 201
Revised value of the eighth-order electron g-2
The contribution to the eighth-order anomalous magnetic moment (g-2) of the
electron from a set of diagrams without closed lepton loops is recalculated
using a new FORTRAN code generated by an automatic code generator. Comparing
the contributions of individual diagrams of old and new calculations, we found
an inconsistency in the old treatment of infrared subtraction terms in two
diagrams. Correcting this error leads to the revised value -1.9144 (35)
(alpha/pi)^4 for the eighth-order term. This theoretical change induces the
shift of the inverse of the fine structure constant by -6.41180(73)x10^{-7}.Comment: 4 pages, 1 figure, typo is correcte
Chk1 requirement for high global rates of replication fork progression during normal vertebrate S phase
Chk1 protein kinase maintains replication fork stability in metazoan cells in response to DNA damage and DNA replication inhibitors. Here, we have employed DNA fiber labeling to quantify, for the first time, the extent to which Chk1 maintains global replication fork rates during normal vertebrate S phase. We report that replication fork rates in Chk1¿/¿ chicken DT40 cells are on average half of those observed with wild-type cells. Similar results were observed if Chk1 was inhibited or depleted in wild-type DT40 cells or HeLa cells by incubation with Chk1 inhibitor or small interfering RNA. In addition, reduced rates of fork extension were observed with permeabilized Chk1¿/¿ cells in vitro. The requirement for Chk1 for high fork rates during normal S phase was not to suppress promiscuous homologous recombination at replication forks, because inhibition of Chk1 similarly slowed fork progression in XRCC3¿/¿ DT40 cells. Rather, we observed an increased number of replication fibers in Chk1¿/¿ cells in which the nascent strand is single-stranded, supporting the idea that slow global fork rates in unperturbed Chk1¿/¿ cells are associated with the accumulation of aberrant replication fork structure
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