Search results for "VERTEX"

Magnetic forces in 2D foams

2005

The asymptotic expression for the ponderomotive force in the magnetic liquid film is derived and a role of the disjoining pressure in 2D magnetic foam formation is considered. New equation for the force balance at the vertex of 2D magnetic foam is proposed and modified Plateau rule for the films is obtained. The theoretical relation for the angle between films fits the experimental data for small magnetic Bond numbers very well.

Stationary states in quantum walk search

2016

When classically searching a database, having additional correct answers makes the search easier. For a discrete-time quantum walk searching a graph for a marked vertex, however, additional marked vertices can make the search harder by causing the system to approximately begin in a stationary state, so the system fails to evolve. In this paper, we completely characterize the stationary states, or 1-eigenvectors, of the quantum walk search operator for general graphs and configurations of marked vertices by decomposing their amplitudes into uniform and flip states. This infinitely expands the number of known stationary states and gives an optimization procedure to find the stationary state c…

On the number of singularities, zero curvature points and vertices of a simple convex space curve

1995

We prove a generalization of the 4 vertex theorem forC3 closed simple convex space curves including singular and zero curvature points.

A four vertex theorem for strictly convex space curves

1993

The energy dependence of Zweig-rule-violating couplings. A dynamical calculation of ϕ → ρπ

1978

It has been argued that the violation of the Zweig rule is strongly dependent on the kinematical region, especially that it should decrease for large timeliket (asymptotic planarity). We have calculated thet-dependence of the vertex ϕρπ with two different methods, the first one using partial-wave dispersion relations and unitarity and the second one based on FESR and duality. The decrease in the timelike region is confirmed by both calculations. In the spacelike region the energy dependence of the Zweig-rule-violating coupling depends on the method of continuation to off-shell values. We only find an energy dependence if the full amplitude πρ → K $$\bar K$$ is taken into account.

The electron gas with a strong pairing interaction: Three particle correlations and the Thouless instability

2000

We derive simplified Faddeev type equations for the three particle T-matrix which are valid in the Hubbard model where only electrons with opposite spins interact. Using the approximation of dynamical mean field theory these equations are partially solved numerically for the attractive Hubbard model. It is shown that the three particle T-matrix contains a term vanishing $\sim T^2$ at the Thouless (or BCS) instability where the two-particle T-matrix diverges. Based on the three particle term we further derive the low density - strong coupling extension for the two-particle vertex function. We therefore understand our equations as a step towards a systematic low density expansion from the wea…

Gamma(Z --> bb): A signature of hard mass terms for a heavy top

1988

Abstract We calculate analytically the weak radiative corrections to the weak neutral current gauge boson-bottom fermion vertex, keeping the mass mt of the internal fermion line for the relevant diagrams. We find, to order α, a hard mass-term dependence m t 2 M W 2 of the amplitude, for large mt values. Its origin comes from the unphysical charged Higgs coupling to fermions in the renormalizable gauge or, equivalently, from the longitudinal charged gauge boson couplings. The diagonal Z0 decay width to b-quarks decreases, due to these weak radiative corrections, by 0.6%–2.5% when the top mass mt varies from 45 to 200 GeV.

φ meson mass and decay width in nuclear matter

2002

The $\phi$ meson spectrum, which in vacuum is dominated by its coupling to the $\bar{K} K$ system, is modified in nuclear matter. Following a model based on chiral SU(3) dynamics we calculate the $\phi$ meson selfenergy in nuclear matter considering the $K$ and $\bar{K}$ in-medium properties. For the latter we use the results of previous calculations which account for $S-$ and $P-$wave kaon-nucleon interactions based on the lowest order meson-baryon chiral effective Lagrangian, and this leads to a dressing of the kaon propagators in the medium. In addition, a set of vertex corrections is evaluated to fulfill gauge invariance, which involves contact couplings of the $\phi$ meson to $S-$wave …

Search for anomalous Wtb couplings in single top quark production

2008

Made available in DSpace on 2022-04-28T20:46:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-11-25 Science and Technology Facilities Council In 0.9fb-1 of pp̄ collisions, the D0 Collaboration presented evidence for single top quark production in events with an isolated lepton, missing transverse momentum, and two to four jets. We examine these data to study the Lorentz structure of the Wtb coupling. The standard model predicts a left-handed vector coupling at the Wtb vertex. The most general lowest dimension, CP-conserving Lagrangian admits right-handed vector and left- or right-handed tensor couplings as well. We find that the data prefer the left-handed vector coupling and set u…

Anti-concentration property for random digraphs and invertibility of their adjacency matrices

2016

Let Dn,dDn,d be the set of all directed d-regular graphs on n vertices. Let G be a graph chosen uniformly at random from Dn,dDn,d and M be its adjacency matrix. We show that M is invertible with probability at least View the MathML source1−Cln3⁡d/d for C≤d≤cn/ln2⁡nC≤d≤cn/ln2⁡n, where c,Cc,C are positive absolute constants. To this end, we establish a few properties of directed d-regular graphs. One of them, a Littlewood–Offord-type anti-concentration property, is of independent interest: let J be a subset of vertices of G with |J|≤cn/d|J|≤cn/d. Let δiδi be the indicator of the event that the vertex i is connected to J and δ=(δ1,δ2,…,δn)∈{0,1}nδ=(δ1,δ2,…,δn)∈{0,1}n. Then δ is not concentrate…