4,221 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
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
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
Locking of accessible information and implications for the security of quantum cryptography
The unconditional security of a quantum key distribution protocol is often
defined in terms of the accessible information, that is, the maximum mutual
information between the distributed key S and the outcome of an optimal
measurement on the adversary's (quantum) system. We show that, even if this
quantity is small, certain parts of the key S might still be completely
insecure when S is used in applications, such as for one-time pad encryption.
This flaw is due to a locking property of the accessible information: one
additional (physical) bit of information might increase the accessible
information by more than one bit.Comment: 5 pages; minor change
Statistical evidence that honeybees competitively reduced wild bee abundance in the Munich Botanic Garden in 2020 compared to 2019
In a commentary on our paper (Renner et al., Oecologia 195:825-831, 2021), Harder and Miksha lay out why they think that our finding of higher honeybee abundances reducing wild bee abundances in an urban botanical garden is not statistically supported. Here, we explain the statistical test provided in our paper, which took advantage of a natural experiment offered by 2019 being a poorer year for bee keeping than 2020
Structure of self-assembled Mn atom chains on Si(001)
Mn has been found to self-assemble into atomic chains running perpendicular
to the surface dimer reconstruction on Si(001). They differ from other atomic
chains by a striking asymmetric appearance in filled state scanning tunneling
microscopy (STM) images. This has prompted complicated structural models
involving up to three Mn atoms per chain unit. Combining STM, atomic force
microscopy and density functional theory we find that a simple necklace-like
chain of single Mn atoms reproduces all their prominent features, including
their asymmetry not captured by current models. The upshot is a remarkably
simpler structure for modelling the electronic and magnetic properties of Mn
atom chains on Si(001).Comment: 5 pages, 4 figure
A measure of majorisation emerging from single-shot statistical mechanics
The use of the von Neumann entropy in formulating the laws of thermodynamics
has recently been challenged. It is associated with the average work whereas
the work guaranteed to be extracted in any single run of an experiment is the
more interesting quantity in general. We show that an expression that
quantifies majorisation determines the optimal guaranteed work. We argue it
should therefore be the central quantity of statistical mechanics, rather than
the von Neumann entropy. In the limit of many identical and independent
subsystems (asymptotic i.i.d) the von Neumann entropy expressions are recovered
but in the non-equilbrium regime the optimal guaranteed work can be radically
different to the optimal average. Moreover our measure of majorisation governs
which evolutions can be realized via thermal interactions, whereas the
nondecrease of the von Neumann entropy is not sufficiently restrictive. Our
results are inspired by single-shot information theory.Comment: 54 pages (15+39), 9 figures. Changed title / changed presentation,
same main results / added minor result on pure bipartite state entanglement
(appendix G) / near to published versio
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