4,604 research outputs found
Higgs mediated Double Flavor Violating top decays in Effective Theories
The possibility of detecting double flavor violating top quark transitions at
future colliders is explored in a model-independent manner using the effective
Lagrangian approach through the () decays. A
Yukawa sector that contemplates invariants of up to
dimension six is proposed and used to derive the most general flavor violating
and CP violating and vertices of renormalizable type.
Low-energy data, on high precision measurements, and experimental limits are
used to constraint the and vertices and then used to
predict the branching ratios for the decays. It is found
that this branching ratios may be of the order of , for a
relative light Higgs boson with mass lower than , which could be more
important than those typical values found in theories beyond the standard model
for the rare top quark decays () or . %% LHC experiments, by using a total integrated luminosity of of data, will be able to rule out, at 95% C.L., DFV top quark
decays up to a Higgs mass of 155 GeV/ or discover such a process up to a
Higgs mass of 147 GeV/.Comment: 24 pages, 11 figure
Tests of Basic Quantum Mechanics in Oscillation Experiments
According to standard quantum theory, the time evolution operator of a
quantum system is independent of the state of the system. One can, however,
consider systems in which this is not the case: the evolution operator may
depend on the density operator itself. The presence of such modifications of
quantum theory can be tested in long baseline oscillation experiments.Comment: 8 pages, LaTeX; no macros neede
Network synchronization: Optimal and Pessimal Scale-Free Topologies
By employing a recently introduced optimization algorithm we explicitely
design optimally synchronizable (unweighted) networks for any given scale-free
degree distribution. We explore how the optimization process affects
degree-degree correlations and observe a generic tendency towards
disassortativity. Still, we show that there is not a one-to-one correspondence
between synchronizability and disassortativity. On the other hand, we study the
nature of optimally un-synchronizable networks, that is, networks whose
topology minimizes the range of stability of the synchronous state. The
resulting ``pessimal networks'' turn out to have a highly assortative
string-like structure. We also derive a rigorous lower bound for the Laplacian
eigenvalue ratio controlling synchronizability, which helps understanding the
impact of degree correlations on network synchronizability.Comment: 11 pages, 4 figs, submitted to J. Phys. A (proceedings of Complex
Networks 2007
The Chagos Islands cases: the empire strikes back
Good governance requires the accommodation of multiple interests in the cause of decision making. However, undue regard for particular sectional interests can take their toll upon public faith in government administration. Historically, broad conceptions of the good of the commonwealth were employed to outweigh the interests of groups that resisted colonisation. In the decision making of the British Empire, the standard approach for justifying the marginalisation of the interests of colonised groups was that they were uncivilised and that particular hardships were the price to be paid for bringing to them the imperial dividend of industrial society. It is widely assumed that with the dismantling of the British Empire, such impulses and their accompanying jurisprudence became a thing of the past. Even as decolonisation proceeded apace after the Second World War, however, the United Kingdom maintained control of strategically important islands with a view towards sustaining its global role. In an infamous example from this twilight period of empire, in the 1960s imperial interests were used to justify the expulsion of the Chagos islanders from the British Indian Ocean Territory (BIOT). Into the twenty-first century, this forced elision of the UK’s interests with the imperial “common good” continues to take centre stage in courtroom battles over the islanders’ rights, being cited before domestic and international tribunals in order to maintain the Chagossians’ exclusion from their homeland. This article considers the new jurisprudence of imperialism which has emerged in a string of decisions which have continued to marginalise the Chagossians’ interests
Cosmic censorship and spherical gravitational collapse with tangential pressure
We study the spherical gravitational collapse of a compact object under the
approximation that the radial pressure is identically zero, and the tangential
pressure is related to the density by a linear equation of state. It turns out
that the Einstein equations can be reduced to the solution of an integral for
the evolution of the area radius. We show that for positive pressure there is a
finite region near the center which necessarily expands outwards, if collapse
begins from rest. This region could be surrounded by an inward moving one which
could collapse to a singularity - any such singularity will necessarily be
covered by a horizon. For negative pressure the entire object collapses
inwards, but any singularities that could arise are not naked. Thus the nature
of the evolution is very different from that of dust, even when the ratio of
pressure to density is infinitesimally small.Comment: 16 pages, Latex file, two figures, uses epsf.st
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