相关论文: Vector Meson Dominance as a first step in a system…
We study a model-independent parameterization of the vector pion form factor that arises from the constraints of analyticity and unitarity. Our description should be suitable up to s^(1/2) ~ 1.2 GeV and allows a model-independent…
We discuss the pion and nucleon form factors and generalized form factors within the large-Nc approach in the space-like region. We estimate their theoretical uncertainties through the use of the half-width rule, amounting to taking the…
We consider row sequences of vector valued Pad\'{e}-Faber approximants (simultaneous Pad\'{e}-Faber approximants) and prove a Montessus de Ballore type theorem.
New, accurate measurements of the pion and kaon electromagnetic form factors are expected in the near future from experiments at electron-positron colliders,using the radiative return method. We construct a model for the timelike pion…
We employ a mathematical framework based on rational approximants in order to calculate meson form factors. The method profits from unitary, is systematic and data based, and is able to ascribe a systematic uncertainty which provides for…
We extend our relativistic theory of electroweak properties of composite systems to describe simultaneously the gravitational form factors of hadrons. The approach is based on a version of the instant-form relativistic quantum mechanics and…
Higher order derivatives of functions are structured high dimensional objects which lend themselves to many alternative representations, with the most popular being multi-index, matrix and tensor representations. The choice between them…
We study the family of intersection graphs of low density objects in low dimensional Euclidean space. This family is quite general, and includes planar graphs. We prove that such graphs have small separators. Next, we present efficient…
In this paper an inexact proximal point method for variational inequalities in Hadamard manifolds is introduced and studied its convergence properties. The main tool used for presenting the method is the concept of enlargement of monotone…
The pion electromagnetic form factor is calculated in the space- and time-like regions from -10 $(GeV/c)^2$ up to 10 $(GeV/c)^2$, within a front-form model. The dressed photon vertex where a photon decays in a quark-antiquark pair is…
Vector Meson Dominance ideas together with a Finite Energy QCD sum rule allows for the determination of the $q^{2}$- and the $T$- dependence of the effective hadronic coupling constant $g_{\rho \pi \pi}$ in the space-like region. It turns…
The form factors of the light pseudoscalar mesons are investigated in a dispersive formalism based on hadronic unitarity, analyticity and the OPE expansion of the QCD Green functions. We propose generalizations of the original mathematical…
We compare the predictions of a range of existing models based on the Vector Meson Dominance hypothesis with data on e^+ e^- -> pi^+ pi^$ and e^+ e^- -> mu^+ mu^- cross-sections and the phase and near-threshold behavior of the timelike pion…
Let $f$ be a power series with positive radius of convergence. In the present paper, we study the phenomenon of overconvergence of sequences of classical Pade' approximants pi{n,m_n} associated with f, where m(n)<=m(n+1)<=m(n) and m(n) =…
The inspiral of two compact objects in gravitational wave astronomy is described by a post-Newtonian expansion in powers of $(v/c)$. In most cases, it is believed that the post-Newtonian expansion is asymptotically divergent. A standard…
We present a calculation of the vector-isovector timelike form-factors of the pion and the kaon using lattice quantum chromodynamics. We calculate two-point correlation functions with $m_\pi \sim 280$ MeV, extracting both the finite-volume…
In a recent paper [1] we have proposed a new approach for extracting the wave function of the $\pi$-meson $\varphi_{\pi}(x)$ and the masses and wave functions of its first resonances from the new QCD sum rules for non-diagonal correlators…
We have used the PIBETA large acceptance detector for a precise measurement of the $\pi^+ \to e^+\nu\gamma$ radiative decay at rest, with broad phase space coverage. Using the CVC value for the pion vector form factor, $F_V = 0.0259(5)$, we…
Bottom-Up Hidden Tree Markov Model is a highly expressive model for tree-structured data. Unfortunately, it cannot be used in practice due to the intractable size of its state-transition matrix. We propose a new approximation which lies on…
Confronted with some surprising claims about experimentally measured or theoretically expected dependencies on the involved momentum transfer of various form factors of pseudoscalar mesons, we reassess the present status of these quantities…