750,641 research outputs found
On the spectral density of the Wilson operator
We summarize our recent determination [1] of the spectral density of the
Wilson operator in the p-regime of Wilson chiral perturbation theory. We
discuss the range of validity of our formula and a possible extension to our
computation in order to better understand the behaviour of the spectral density
in a finite volume close to the threshold.Comment: 7 pages, 2 figures, Proceedings for the XXIX International Symposium
on Lattice Field Theor
Tree-level scattering amplitudes from the amplituhedron
7 pages, 2 figures, to be published in the Journal of Physics: Conference Series. Proceedings for the "7th Young Researcher Meeting", Torino, 2016A central problem in quantum field theory is the computation of scattering amplitudes. However, traditional methods are impractical to calculate high order phenomenologically relevant observables. Building on a few decades of astonishing progress in developing non-standard computational techniques, it has been recently conjectured that amplitudes in planar N=4 super Yang-Mills are given by the volume of the (dual) amplituhedron. After providing an introduction to the subject at tree-level, we discuss a special class of differential equations obeyed by the corresponding volume forms. In particular, we show how they fix completely the amplituhedron volume for next-to-maximally helicity violating scattering amplitudes.Peer reviewe
Finite-volume corrections to the leading-order hadronic contribution to
We present preliminary results of a 2+1-flavor study of finite-volume effects
in the lattice QCD computation of the leading-order hadronic contribution to
the muon anomalous magnetic moment. We also present methods for obtaining
directly the invariant hadronic polarization function, , and the
Adler function at all discrete lattice values of , including .
Results are obtained with HEX-smeared clover fermions.Comment: 7 pages, 2 figures, Contribution to the Proceedings of the 32nd
International Symposium on Lattice Field Theory (Lattice 2014), 23-28 June
2014, Columbia University, New York, NY, US
Fluxbrane Inflation
As a first step towards inflation in genuinely F-theoretic setups, we propose
a scenario where the inflaton is the relative position of two 7-branes on
holomorphic 4-cycles. Non-supersymmetric gauge flux induces an attractive
inter-brane potential. The latter is sufficiently flat in the supergravity
regime of large volume moduli. Thus, in contrast to brane-antibrane inflation,
fluxbrane inflation does not require warping. We calculate the inflaton
potential both in the supergravity approximation and via an open-string
one-loop computation on toroidal backgrounds. This leads us to propose a
generalisation to genuine Calabi-Yau manifolds. We also comment on competing
F-term effects. The end of inflation is marked by the condensation of tachyonic
recombination fields between the 7-branes, triggering the formation of a bound
state described as a stable extension along the 7-brane divisor. Hence our
model fits in the framework of hybrid D-term inflation. We work out the main
phenomenological properties of our D-term inflaton potential. In particular,
our scenario of D7/D7 inflation avoids the familiar observational constraints
associated with cosmic strings.Comment: 49 pages, 3 figures; v3: refs adde
Estimating the size of the solution space of metabolic networks
In this work we propose a novel algorithmic strategy that allows for an
efficient characterization of the whole set of stable fluxes compatible with
the metabolic constraints. The algorithm, based on the well-known Bethe
approximation, allows the computation in polynomial time of the volume of a non
full-dimensional convex polytope in high dimensions. The result of our
algorithm match closely the prediction of Monte Carlo based estimations of the
flux distributions of the Red Blood Cell metabolic network but in incomparably
shorter time. We also analyze the statistical properties of the average fluxes
of the reactions in the E-Coli metabolic network and finally to test the effect
of gene knock-outs on the size of the solution space of the E-Coli central
metabolism.Comment: 8 pages, 7 pdf figure
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