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We investigated the electronic structure of the enigmatic CeRh$_3$B$_2$ using resonant inelastic scattering and x-ray absorption spectroscopy in combination with $ab$ $initio$ density functional calculations. We find that the Rh 4$d$ states are irrelevant for the high-temperature ferromagnetism and the Kondo effect. We also find that the Ce 4$f$ crystal-field strength is too small to explain the strong reduction of the Ce magnetic moment. The data reveal instead the presence of two different active Ce 4$f$ orbitals, with each coupling selectively to different bands in CeRh$_3$B$_2$. The inter-site hybridization of the |J=5/2,Jz=+/-1/2> crystal-field state and Ce 5$d$ band combined with the intra-site Ce 4$f$-5$d$ exchange creates the strong ferromagnetism, while hybridization between the |J=5/2,Jz=+/-5/2> and the B $sp$ in the $ab$-plane contributes to the Kondo interaction which causes the moment reduction. This orbital selective coupling explains the unique and seemingly contradictory properties of CeRh$_3$B$_2$., Comment: 15 pages, 14 figures

The Discrete elastic rod method (Bergou et al., 2008) is a numerical method for simulating slender elastic bodies. It works by representing the center-line as a polygonal chain, attaching two perpendicular directors to each segment, and defining discrete stretching, bending and twisting deformation measures and a discrete strain energy. Here, we investigate an alternative formulation of this model based on a simpler definition of the discrete deformation measures. Both formulations are equally consistent with the continuous rod model. Simple formulas for the first and second gradients of the discrete deformation measures are derived, making it easy to calculate the Hessian of the discrete strain energy. A few numerical illustrations are given. The approach is also extended to inextensible ribbons described by the Wunderlich model, and both the developability constraint and the dependence of the energy of the strain gradients are handled naturally.

Actuation remains a signifcant challenge in soft robotics. Actuation by light has important advantages: objects can be actuated from a distance, distinct frequencies can be used to actuate and control distinct modes with minimal interference and signifcant power can be transmitted over long distances through corrosion-free, lightweight fiber optic cables. Photo-chemical processes that directly convert photons to configurational changes are particularly attractive for actuation. Various researchers have demonstrated light-induced actuation with liquid crystal elastomers combined with azobenzene photochromes. We present a simple modeling framework and a series of examples that studies actuation by light. Of particular interest is the generation of cyclic or periodic motion under steady illumination. We show that this emerges as a result of a coupling between light absorption and deformation. As the structure absorbs light and deforms, the conditions of illumination change, and this in turn changes the nature of further deformation. This coupling can be exploited in either closed structures or with structural instabilities to generate cyclic motion.

The zero-error capacity of channels with a countably infinite input alphabet formally generalises Shannon's classical problem about the capacity of discrete memoryless channels. We solve the problem for three particular channels. Our results are purely combinatorial and in line with previous work of the third author about permutation capacity., Comment: 8 pages

We determine the asymptotics of the largest cardinality of a set of Hamilton paths in the complete graph with vertex set [n] under the condition that for any two of the paths in the family there is a subpath of length k entirely contained in only one of them and edge{disjoint from the other one.

We examine the four-quark structure of the recently discovered charged $Z_c(3900)$, $Z(4430)$, and $X_b(5568)$ states. We calculate the widths of the strong decays $Z_c^+ \to J/\psi \pi^+$ ($\eta_c\rho^+$, $\bar D^0D^{\ast\,+}$, $\bar D^{\ast\,0}D^+$), $Z(4430)^+ \to J/\psi \pi^+$ ($\psi(2s) \pi^+$), and $X^+_b\to B_s\pi^+$ within a covariant quark model previously developed by us. We find that the tetraquark-type current widely used in the literature for the $Z_c(3900)$ leads to a significant suppression of the $\bar D D^\ast$ and $\bar D^\ast D$ modes. Contrary to this a molecular-type current provides an enhancement by a factor of 6-7 for the $\bar D D^\ast$ modes compared with the $Z_c^+\to J/\psi\pi^+$, $\eta_c\rho^+$ modes in agreement with recent experimental data from the BESIII Collaboration. In case of the $Z(4430)$ state we test a sensitivity of the ratio $R_Z$ of the $Z(4430)^+ \to \psi(2s) \pi^+$ and $Z(4430)^+ \to J/\psi \pi^+$ decay rates to a choice of the size parameter $\Lambda_{Z(4430)}$ of the $Z(4430)$. Using upper constraint for the sum of these two modes deduced from the LHCb Collaboration data we find that $R_Z$ varies from 4.64 to 4.08 when $\Lambda_{Z(4430)}$ changes from 2.2 to 3.2 GeV. Also we make the prediction for the $Z(4430)^+ \to D^{\ast\,+} \bar D^{\ast\,0}$ decay rate., Comment: 14 pages

We present results for the isotriplet and isosinglet tensor form factors of the nucleon in the relativistic confined quark model. The model allows us to calculate not only their normalizations at $Q^2=0$ and the related tensor charges, but also the full $Q^2$-dependence. Our results are compared to existing data and predictions of other theoretical approaches. We stress the importance of these form factors for the phenomenology of physics beyond the Standard Model., Comment: 7 pages

We present a study of the isospin-violating one-pion strong decays of single heavy tetraquarks $X_Q = X(s q \bar q \bar Q)$, $Q=c, b$, and $q=u, d$ with spin-parity $J^P = 0^+$. We assume that the tetraquarks have the configuration of a color diquark and a antidiquark. Three mechanisms of isospin violation can contribute to the decay rate: (1) mixing of the $X(s u \bar u \bar Q)$ and $X(s d \bar d \bar Q)$ tetraquark currents, (2) an explicit $m_d-m_u$ quark mass difference in the quark diagrams describing the corresponding decay transitions and (3) $\pi^0-\eta$ mixing in the final state. Our main results are: (1) It is quite likely that the investigated tetraquark states are isosinglet states with a small admixture of an isotriplet component; (2) The first isospin-breaking mechanism affects the decay rater more significantly than the others; (3) Our calculations contain a size parameter $\Lambda_{X_Q}$, characterizing the distribution of the quarks in the tetraquark state $X_Q$. Absolute decay rates depend very much on the choice of $\Lambda_{X_Q}$, varied from 1 to 2 GeV, reflecting the compactness of the multiquark system., Comment: 13 pages

We present precise theoretical predictions for the absolute branching fractions of $\Lambda_c^+ \to \Lambda \ell^+ \nu_\ell\,(\ell=e,\mu)$ decays in the covariant confined quark model. This study is motivated by two recent and accurate measurements of the absolute branching fractions of $\Lambda_c^+ \to p K^- \pi^+$ and $\Lambda_c^+ \to \Lambda e^+ \nu_e$ by the Belle Collaboration at the KEKB and by the BESIII Collaboration at the BEPCII. Our predictions for the branching fractions are consistent with both experimental results. We also provide detailed numerical results for differential decay distributions and polarization observables., Comment: 7 pages. arXiv admin note: substantial text overlap with arXiv:1502.04864

Recently the ATLAS Collaboration at CERN reported on the measurement of the branching ratio R(Lambda_b) = Gamma(Lambda_b(0) -> psi(2S) Lambda(0))/Gamma(Lambda_b(0) -> J/psi Lambda(0)). The measured branching ratio R(Lambda_b) = 0.501 pm 0.033$ (stat) pm 0.019 (syst) was found to be lower than the covariant quark model prediction of R(Lambda_b) = 0.8 pm 0.1 calculated by us recently. We present a detailed analysis of the branching ratio R(Lambda_b) using a model-independent framework for the heavy-to-light form factors based on results from our previos papers., Comment: 6 pages

Recently there has been much interest in the tauonic semileptonic meson decays B -> D + tau + nu_tau and B -> D* + tau + nu_tau where one has found larger rates than what is predicted by the Standard Model. We analyze the corresponding semileptonic baryon decays Lambda_b(0) -> Lambda_c(+) + tau(-) + antinu_tau with particular emphasis on the lepton helicity flip and scalar contributions which vanish for zero lepton masses. We calculate the total rate, differential decay distributions, the longitudinal and transverse polarization of the daughter baryon Lambda_c(+) and the tau-lepton, and the lepton-side forward-backward asymmetries. The nonvanishing polarization of the daughter baryon Lambda_c(+) leads to hadron-side asymmetries in e.g. the decay Lambda_c(+) -> Lambda(0) + pi(+) and azimuthal correlations between the two final state decay planes which we specify. We provide numerical results on these observables using results of the covariant confined quark model. We find large lepton mass effects in the q2-spectra and in the polarization observables., Comment: 26 pages

We improve by an exponential factor the lower bound of Korner and Muzi for the cardinality of the largest family of Hamilton paths in a complete graph of n vertices in which the union of any two paths has degree 4. The improvement is through an explicit construction while the previous bound was obtained by a greedy algorithm. We solve a similar problem for permutations up to an exponential factor., Comment: In this version an error in the previous manuscript is corrected

We present a detailed analysis of the heavy-to-light semileptonic decays of the Lambda_b and Lambda_c baryons Lambda_b -> p l- bar(nu)_l and Lambda_c -> n l+ nu_l in the covariant confined quark model. We calculate the invariant and helicity amplitudes of the two processes which are then used to analyze their angular decay distributions, their rates and asymmetry parameters., Comment: 10 pages

For the upgrade of the ATLAS muon spectrometer in March 2014 new muon tracking chambers (sMDT) with drift-tubes of 15 mm diameter, half of the value of the standard ATLAS Monitored Drift-Tubes (MDT) chambers, and 10~$\mu$m positioning accuracy of the sense wires have been constructed. The new chambers are designed to be fully compatible with the present ATLAS services but, with respect to the previously installed ATLAS MDT chambers, they are assembled in a more compact geometry and they deploy two additional tube layers that provide redundant rack information. The chambers are composed of 8 layers of in total 624 aluminium drift-tubes. The assembly of a chamber is completed within a week. A semi-automatized production line is used for the assembly of the drift-tubes prior to the chamber assembly. The production procedures and the quality control tests of the single components and of the complete chambers will be discussed. The wire position in the completed chambers have been measured by using a coordinate measuring machine., Comment: 4 pages, 4 figures, 1 table. Proceeding for TIPP 2014

We calculate the invariant and helicity amplitudes for the nonleptonic decay Lambda_b -> Lambda + J/psi, psi(2S) in the covariant confined quark model. We discuss joint angular decay distributions in the cascade decay Lambda_b -> Lambda(-> p pi-) + J/psi, psi(2S) (-> l+ l-) and calculate some of the asymmetry parameters that characterize the joint angular decay distribution. We confirm expectations from the naive quark model that the transitions into the lambda_Lambda=1/2 helicity states of the daughter baryon Lambda are strongly suppressed leading to a near maximal negative polarization of the Lambda. For the same reason the azimuthal correlation between the two decay planes spanned by (p pi-) and (l+ l-) is negligibly small. We provide form factor results for the whole accessible q2-range. Our results are close to lattice results at minimum recoil and light-cone sum rule results at maximum recoil. A new feature of our analysis is that we include lepton mass effects in the calculation which allows us to also describe the cascade decay Lambda_b -> Lambda(-> p pi-) + psi(2S)(-> tau+ tau-)., Comment: 18 pages

In a Perspectives article in Science, Bradley Efron concludes that Bayesian calculations cannot be uncritically accepted when using uninformative priors. We argue that this conclusion is problematic because Efron's example does not use data, hence it is not Bayesian statistics; his priors make little sense and are not uninformative; and using the available data point and an uninformative prior actually leads to a reasonable posterior distribution., Comment: 3 pages