5,206 research outputs found
Detection of Laplace-resonant three-planet systems from transit timing variations
Transit timing variations (TTVs) are useful to constrain the existence of
perturbing planets, especially in resonant systems where the variations are
strongly enhanced. Here we focus on Laplace-resonant three-planet systems, and
assume the inner planet transits the star. A dynamical study is performed for
different masses of the three bodies, with a special attention to terrestrial
planets. We consider a maximal time-span of ~ 100 years and discuss the shape
of the inner planet TTVs curve. Using frequency analysis, we highlight the
three periods related to the evolution of the system: two periods associated
with the Laplace-resonant angle and the third one with the precession of the
pericenters. These three periods are clearly detected in the TTVs of an inner
giant planet perturbed by two terrestrial companions. Only two periods are
detected for a Jupiter-Jupiter-Earth configuration (the ones associated with
the giant interactions) or for three terrestrial planets (the Laplace periods).
However, the latter system can be constrained from the inner planet TTVs. We
finally remark that the TTVs of resonant three or two Jupiter systems mix up,
when the period of the Laplace resonant angle matches the pericenter precession
of the two-body configuration. This study highlights the importance of TTVs
long-term observational programs for the detection of multiple-planet resonant
systems.Comment: 8 pages, 8 figures, accepted in MNRA
Large Hadron Collider constraints on a light baryon number violating sbottom coupling to a top and a light quark
We investigate a model of R-parity violating (RPV) supersymmetry in which the
right-handed sbottom is the lightest supersymmetric particle, and a baryon
number violating coupling involving a top is the only non-negligible RPV
coupling. This model evades proton decay and flavour constraints. We consider
in turn each of the couplings lambda"_{313} and lambda"_{323} as the only
non-negligible RPV coupling, and we recast two recent Large Hadron Collider
(LHC) measurements and searches (CMS top transverse momentum p_T(t) spectrum
and ATLAS multiple jet resonance search) in the form of constraints on the
mass-coupling parameter planes. We delineate a large region in the parameter
space of the mass of the sbottom (m_{b_R}) and the lambda"_{313} coupling that
is ruled out by the measurements, as well as a smaller region in the parameter
space of m_{b_R} and lambda"_{323}. A certain region of the
m_{b_R}-lambda"_{313} parameter space was previously found to successfully
explain the anomalously large ttbar forward backward asymmetry measured by
Tevatron experiments. The entire region is excluded at the 95% CL by CMS
measurements of the top p_T spectrum. We also present p_T(ttbar) distributions
of the forward-backward asymmetry for this model.Comment: 9 pages, 9 figures. v2 has minor corrections, in part due to extra
diagrams at order alpha_s^2 lamba''^
Linear flavour violation and anomalies in B physics
We propose renormalizable models of new physics that can explain various
anomalies observed in decays of B-mesons to electron and muon pairs. The new
physics states couple to linear combinations of Standard Model fermions,
yielding a pattern of flavour violation that gives a consistent fit to the
gamut of flavour data. Accidental symmetries prevent contributions to baryon-
and lepton-number-violating processes, as well as enforcing a loop suppression
of new physics contributions to flavour violating processes. Data require that
the new flavour-breaking couplings are largely aligned with the Yukawa
couplings of the SM and so we also explore patterns of flavour symmetry
breaking giving rise to this structure.Comment: v2: 28 pages, 10 figures. Added two appendices to make the SU(2)
structure of the model clearer, and to discuss Z/photon penguin
contributions. Updated a bound on Bs mixing, and added references.
Conclusions unchanged. Version to appear in JHE
Hint of Lepton Flavour Non-Universality in Meson Decays
The LHCb collaboration has recently presented their result on R_K = BR(B+ ->
K+ mu+ mu-)/ BR(B+ -> K+ e+ e-) for the dilepton invariant mass bin m_{ll}^2 =
1-6 GeV^2 (l = mu, e). The measurement shows an intriguing 2.6 sigma deviation
from the Standard Model (SM) prediction. In view of this, we study model
independent New Physics (NP) explanations of R_K consistent with other
measurements involving b -> s l l transition, relaxing the assumption of lepton
universality. We perform a Bayesian statistical fit to the NP Wilson
Coefficients and compare the Bayes Factors of the different hypotheses in order
to quantify their goodness-of-fit. We show that the data slightly favours NP in
the muon sector over NP in the electron sector.Comment: Final version, to appear in JHE
Comment on "Indispensable Finite Time Correlations for Fokker-Planck Equations from Time Series Data"
Comment on "Indispensable Finite Time Correlations for Fokker-Planck
Equations from Time Series Data"Comment: 2 pages, 1 figur
On giant piezoresistance effects in silicon nanowires and microwires
The giant piezoresistance (PZR) previously reported in silicon nanowires is
experimentally investigated in a large number of surface depleted silicon nano-
and micro-structures. The resistance is shown to vary strongly with time due to
electron and hole trapping at the sample surfaces. Importantly, this time
varying resistance manifests itself as an apparent giant PZR identical to that
reported elsewhere. By modulating the applied stress in time, the true PZR of
the structures is found to be comparable with that of bulk silicon
Pollination by flies, bees, and beetles of Nuphar ozarkana and N. advena (Nymphaeaceae)
Nuphar comprises 13 species of aquatic perennials distributed in the temperate Northern Hemisphere. The European species N. lutea and N. pumila in Norway, the Netherlands, and Germany are pollinated by bees and flies, including apparent Nuphar specialists. This contrasts with reports of predominant beetle pollination in American N. advena and N. polysepala. We studied pollination in N. ozarkana in Missouri and N. advena in Texas to assess whether (1) there is evidence of pollinator shifts associated with floral-morphological differences between Old World and New World species as hypothesized by Padgett, Les, and Crow (American Journal of Botany 86: 1316–1324. 1999) and (2) whether beetle pollination characterizes American species of Nuphar. Ninety-seven and 67% of flower visits in the two species were by sweat bees, especially Lasioglossum (Evylaeus) nelumbonis. Syrphid fly species visiting both species were Paragus sp., Chalcosyrphus metallicus, and Toxomerus geminatus. The long-horned leaf beetle Donacia piscatrix was common on leaves and stems of N. ozarkana but rarely visited flowers. Fifteen percent of visits to N. advena flowers were by D. piscatrix and D. texana. The beetles’
role as pollinators was investigated experimentally by placing floating mesh cages that excluded flies and bees over N. advena buds about to open and adding beetles. Beetles visited 40% of the flowers in cages, and flowers that received visits had 69% seed set, likely due to beetle-mediated geitonogamy of 1st-d flowers. Experimentally outcrossed 1st-d flowers had 62% seed set, and open-pollinated flowers 76%; 2nd-d selfed or outcrossed flowers had low seed sets (9 and 12%, respectively). Flowers are strongly protogynous and do not self spontaneously. Flowers shielded from pollinators set no seeds. A comparison of pollinator spectra in the two Old World and three New World Nuphar species studied so far suggests that the relative contribution of flies, bees, and beetles to pollen transfer in any one population depends more on these insects’ relative abundances (and in the case of Donacia, presence) and alternative food sources than on stamen length differences between Old World and New World pond-lilies
Device independent quantum key distribution secure against coherent attacks with memoryless measurement devices
Device independent quantum key distribution aims to provide a higher degree
of security than traditional QKD schemes by reducing the number of assumptions
that need to be made about the physical devices used. The previous proof of
security by Pironio et al. applies only to collective attacks where the state
is identical and independent and the measurement devices operate identically
for each trial in the protocol. We extend this result to a more general class
of attacks where the state is arbitrary and the measurement devices have no
memory. We accomplish this by a reduction of arbitrary adversary strategies to
qubit strategies and a proof of security for qubit strategies based on the
previous proof by Pironio et al. and techniques adapted from Renner.Comment: 13 pages. Expanded main proofs with more detail, miscellaneous edits
for clarit
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