61,181 research outputs found
Impact of FCNC top quark interactions on BR(t -> b W)
We study the effect that FCNC interactions of the top quark will have on the
branching ratio of charged decays of the top quark. We have performed an
integrated analysis using Tevatron and B-factories data and with just the
further assumption that the CKM matrix is unitary we can obtain very
restrictive bounds on the strong and electroweak FCNC branching ratios Br(t ->
q X) < 4.0 10^{-4}, where X is any vector boson and a sum in q = u,c is
implied.Comment: 10 pages, 5 figure
Contributions from dimension six strong flavor changing operators to top anti-top, top plus gauge boson, and top plus Higgs boson production at the LHC
We study the effects of a set of dimension six flavor changing effective
operators on several processes of production of top quarks at the LHC. Namely,
top anti-top production and associated production of a top and a gauge or Higgs
boson. Analytical expressions for the cross sections of these processes are
derived and presented.Comment: 14 pages, 10 figures, refs. adde
Efficient Enumeration of Induced Subtrees in a K-Degenerate Graph
In this paper, we address the problem of enumerating all induced subtrees in
an input k-degenerate graph, where an induced subtree is an acyclic and
connected induced subgraph. A graph G = (V, E) is a k-degenerate graph if for
any its induced subgraph has a vertex whose degree is less than or equal to k,
and many real-world graphs have small degeneracies, or very close to small
degeneracies. Although, the studies are on subgraphs enumeration, such as
trees, paths, and matchings, but the problem addresses the subgraph
enumeration, such as enumeration of subgraphs that are trees. Their induced
subgraph versions have not been studied well. One of few example is for
chordless paths and cycles. Our motivation is to reduce the time complexity
close to O(1) for each solution. This type of optimal algorithms are proposed
many subgraph classes such as trees, and spanning trees. Induced subtrees are
fundamental object thus it should be studied deeply and there possibly exist
some efficient algorithms. Our algorithm utilizes nice properties of
k-degeneracy to state an effective amortized analysis. As a result, the time
complexity is reduced to O(k) time per induced subtree. The problem is solved
in constant time for each in planar graphs, as a corollary
Bouncing Eddington-inspired Born-Infeld cosmologies: an alternative to Inflation ?
We study the dynamics of a homogeneous and isotropic
Friedmann-Robertson-Walker universe in the context of the Eddington-inspired
Born-Infeld theory of gravity. We generalize earlier results, obtained in the
context of a radiation dominated universe, to account for the evolution of a
universe permeated by a perfect fluid with an arbitrary equation of state
parameter . We show that a bounce may occur for , if is
time-dependent, and we demonstrate that it is free from tensor singularities.
We argue that Eddington-inspired Born-Infeld cosmologies may be a viable
alternative to the inflationary paradigm as a solution to fundamental problems
of the standard cosmological model.Comment: 4 pages, 1 figur
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