Heavy Higgs bosons and the 2 TeV W′W' boson

The hints from the LHC for the existence of a $W'$ boson of mass around 1.9 TeV point towards a certain $SU(2)_L\times SU(2)_R\times U(1)_{B-L}$ gauge theory with an extended Higgs sector. We show that the decays of the $W'$ boson into heavy Higgs bosons have sizable branching fractions. Interpreting the ATLAS excess events in the search for same-sign lepton pairs plus $b$ jets as arising from $W'$ cascade decays, we estimate that the masses of the heavy Higgs bosons are in the 400--700 GeV range.Comment: 22 pages; v2: Eqs. 3.6 and 3.8 corrected, clarifications and references adde

An information-theoretic on-line update principle for perception-action coupling

Inspired by findings of sensorimotor coupling in humans and animals, there has recently been a growing interest in the interaction between action and perception in robotic systems [Bogh et al., 2016]. Here we consider perception and action as two serial information channels with limited information-processing capacity. We follow [Genewein et al., 2015] and formulate a constrained optimization problem that maximizes utility under limited information-processing capacity in the two channels. As a solution we obtain an optimal perceptual channel and an optimal action channel that are coupled such that perceptual information is optimized with respect to downstream processing in the action module. The main novelty of this study is that we propose an online optimization procedure to find bounded-optimal perception and action channels in parameterized serial perception-action systems. In particular, we implement the perceptual channel as a multi-layer neural network and the action channel as a multinomial distribution. We illustrate our method in a NAO robot simulator with a simplified cup lifting task.Comment: 8 pages, 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS

Topological Zero-Thickness Cosmic Strings

In this paper, based on the gauge potential decomposition and the $\phi-$mapping theories, we study the topological structures and properties of the cosmic strings that arise in the Abelian-Higgs gauge theory in the zero-thickness limit. After a detailed discussion, we conclude that the topological tensor current introduced in our model is a better and more basic starting point than the generally used Nambu-Goto effective action for studying cosmic strings.Comment: 10 pages, no figure

Topological view on magnetic adatoms in graphene

We study theoretically the physical properties of a magnetic impurity in graphene. Within the Anderson model for a very strong Coulomb interaction on the impurity, we start from the Slave-Boson method and introduce a topological picture consisting of a degree of a map and a winding number (WN) to analyze the phase shift and the occupation on the impurity. The occupation is linked to WN. For a generic normal metal we find a fractional WN. In contrast, the winding is accelerated by the relativistic dispersion of graphene at half-filling leading to an integer occupation. We show that the renormalization parameter that shifts the impurity level is insufficient to invert the sign of the energy level. Consequently, the state at half-filling is stable unless a gate voltage is tuned such that the Fermi level touches the edge of the broadened impurity level. Only in this case the zero field susceptibility is finite and shows a pronounced peak structure with the gate voltage.Comment: 9pages. 4 figure

Formation and Stability of Cellular Carbon Foam Structures:An {\em Ab Initio} Study

We use ab initio density functional calculations to study the formation and structural as well as thermal stability of cellular foam-like carbon nanostructures. These systems with a mixed $sp^2/sp^3$ bonding character may be viewed as bundles of carbon nanotubes fused to a rigid contiguous 3D honeycomb structure that can be compressed more easily by reducing the symmetry of the honeycombs. The foam may accommodate the same type of defects as graphene, and its surface may be be stabilized by terminating caps. We postulate that the foam may form under non-equilibrium conditions near grain boundaries of a carbon-saturated metal surface

B→a1(1260)a1(1260)B \to a_1(1260) a_1(1260) and b1(1235)b1(1235)b_1(1235) b_1(1235) decays in the perturbative QCD approach

In this work, we study six tree-dominated $B \to a_1(1260) a_1(1260)$ and $b_1(1235) b_1(1235)$ decays in the perturbative QCD(pQCD) approach, where $a_1$($b_1$) is a $^3P_1$($^1P_1$) axial-vector meson. Based on the perturbative calculations and phenomenological analysis, we find that: (a) the CP-averaged branching ratio of $B^0 \to a_1^+ a_1^-$ decay in the pQCD approach is $54.7 \times 10^{-6}$, which agrees well with the current data and the predictions given in the QCD factorization approach within errors; (b) the numerical results for the decay rates of other five channels are found to be in the order of $10^{-6} \sim 10^{-5}$, which could be accessed at B factories and Large Hadron Collider(LHC) experiments; (c) other physical observables such as polarization fractions and direct CP-violating asymmetries are also investigated with the pQCD approach in the present work and the predictions can be confronted with the relevant experiments in the near future; (d) the different phenomenologies shown between $B \to a_1 a_1$ and $B \to b_1 b_1$ decays are expected to be tested by the ongoing LHC and forthcoming Super-B experiments, which could shed light on the typical QCD dynamics involved in these decay modes, as well as in $^3P_1$ meson $a_1$ and $^1P_1$ meson $b_1$.Comment: 1 figure, 27 pages, references added, improved version. Accepted for publication in Phys. Rev.

Nucleation of stable cylinders from a metastable lamellar phase in a diblock copolymer melt

The nucleation of a droplet of stable cylinder phase from a metastable lamellar phase is examined within the single-mode approximation to the mean-field Landau–Brazovskii model for diblock copolymer melts. By employing a variational ansatz for the droplet interfacial profile, an analytic expression for the interfacial free energy of an interface of arbitrary orientation between cylinders and lamellae is found. The interfacial free energy is anisotropic and is lower when the cylinder axis is perpendicular to the interface than when the cylinders lie along the interface. Consequently, the droplet shape computed via the Wulff construction is lens like, being flattened along the axis of the cylinders. The size of the critical droplet and the nucleation barrier are determined within classical nucleation theory. Near the lamellar–cylinder phase boundary, where classical nucleation theory is applicable, critical droplets of size 30–400 cylinders across with aspect ratios of 4–10 and nucleation barriers of (30–40)kBT are typically found. The general trend is to larger critical droplets, higher aspect ratios, and smaller nucleation barriers as the mean-field critical point is approached

Self-organized critical behavior: the evolution of frozen spin networks model in quantum gravity

In quantum gravity, we study the evolution of a two-dimensional planar open frozen spin network, in which the color (i.e. the twice spin of an edge) labeling edge changes but the underlying graph remains fixed. The mainly considered evolution rule, the random edge model, is depending on choosing an edge randomly and changing the color of it by an even integer. Since the change of color generally violate the gauge invariance conditions imposed on the system, detailed propagation rule is needed and it can be defined in many ways. Here, we provided one new propagation rule, in which the involved even integer is not a constant one as in previous works, but changeable with certain probability. In random edge model, we do find the evolution of the system under the propagation rule exhibits power-law behavior, which is suggestive of the self-organized criticality (SOC), and it is the first time to verify the SOC behavior in such evolution model for the frozen spin network. Furthermore, the increase of the average color of the spin network in time can show the nature of inflation for the universe.Comment: 5 pages, 5 figure