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A. I. Veselov

Publications and source records attributed to A. I. Veselov.

At least 37 records · Page 2Linked to original sources
arXiv2008

On the interrelation between monopoles, vortices, topological charge and chiral symmetry breaking: an analysis using overlap fermions for SU(2)

We study the properties of configurations from which P-vortices on one hand or Abelian monopoles on the other hand have been removed. We find that the zero modes and the band of non-zero modes close to zero disappear from the spectrum of the overlap Dirac operator, confirming the absence of topological charge and quark condensate. The different behavior of the modified ensembles under smearing compared to the unmodified Monte Carlo ensemble corroborates these findings. The gluonic topological susceptibility rapidly approaches zero in accordance with Q_{index}=0. The remaining (ultraviolet) monopoles without vortices and -- to a less extent -- the remaining vortices without monopoles are unstable under smearing whereas smearing of the unmodified Monte Carlo ensemble effects the monopoles and vortices only by smoothing, reducing the density only slightly.

hep-lat↗
arXiv2008

Lattice study of monopoles in the Electroweak theory

We investigated numerically properties of Nambu monopoles in lattice Electroweak theory at realistic values of $α$ and $θ_W$. Our choice of parameters of lattice Lagrangian corresponds to large values of the Higgs boson mass $M_H > 2 M_W$. We find that the density of Nambu monopoles cannot be predicted by the choice of the initial parameters of Electroweak theory and should be considered as the new external parameter of the theory. We also investigate the difference between the versions of Electroweak theory with the gauge groups $SU(2)\otimes U(1)$ and $SU(2)\otimes U(1)/Z_2$. We do not detect any difference at $α\sim {1/128}$. However, such a difference appears in the strong coupling region and is related to the properties of monopoles constructed of the hypercharge field.

hep-lat↗
arXiv2007

P Wave Baryons in Field Correlator Method: Hyperons

We provide an investigation of the P-wave hyperons employing the field correlator method in QCD. This method allows to derive the Effective Hamiltonian successfully applied to the meson and ground state baryon spectra. The hyperon spectrum appears to be expressed through two parameters relevant to QCD, the string tension σ, the strong coupling constant α_s, and the bare strange quark mass m_s. Using these parameters a unified description of the ground and excited hyperon states is achieved. We also briefly consider the nucleon P-wave excitations. In particular, we predict that both the nucleon and hyperon states have the similar cost (in ΔL) ~460 MeV.

hep-ph↗
arXiv2007

Calorons and dyons at the thermal phase transition analyzed by overlap fermions

In a pilot study, we use the topological charge density defined by the eigenmodes of the overlap Dirac operator (with ultraviolet filtering by mode-truncation) to search for lumps of topological charge in SU(2) pure gauge theory. Augmenting this search with periodic and antiperiodic temporal boundary conditions for the overlap fermions, we demonstrate that the lumps can be classified either as calorons or as separate caloron constituents (dyons). Inside the topological charge clusters the (smeared) Polyakov loop is found to show the typical profile characteristic for calorons and dyons. This investigation, motivated by recent caloron/dyon model studies, is performed at the deconfinement phase transition for SU(2) gluodynamics on 20^3 x 6 lattices described by the tadpole improved Lüscher-Weisz action. The transition point has been carefully located. As a necessary condition for the caloron/dyon detection capability, we check that the LW action, in contrast to the Wilson action, generates lattice ensembles, for which the overlap Dirac eigenvalue spectrum smoothly behaves under smearing and under the change of the boundary conditions.

hep-lat↗
arXiv2006

Inclusive pentaquark and strange baryons production in hadron beam experiments at high energy

We estimate the high-energy behavior of the $Θ^+$ and $Λ(1520)$ production cross sections in inclusive $pp$ collisions using the $K$ exchange diagram. We show that the cross section of the $Θ^+$-production is suppressed compared to the production of $Λ(1520)$. As a byproduct we also estimate the contribution of the $π$ exchange diagram for the inclusive $Λ(1520)$ production in $Σp$ collisions.

hep-ph↗
arXiv2006

Topology and confinement at T \neq 0 : calorons with non-trivial holonomy

In this talk, relying on experience with various lattice filter techniques, we argue that the semiclassical structure of finite temperature gauge fields for T < T_c is dominated by calorons with non-trivial holonomy. By simulating a dilute gas of calorons with identical holonomy, superposed in the algebraic gauge, we are able to reproduce the confining properties below T_c up to distances r = O(4 fm} >> ρ(the caloron size). We compute Polyakov loop correlators as well as space-like Wilson loops for the fundamental and adjoint representation. The model parameters, including the holonomy, can be inferred from lattice results as functions of the temperature.

hep-ph↗
arXiv2006

Once more on the interrelation between Abelian monopoles and P-vortices in SU(2) LGT

We study the properties of configurations from which P-vortices on one hand or Abelian monopoles on the other hand have been removed. We confirm the loss of confinement in both cases and investigate in what respect the modified ensembles differ from the confining ones from the point of view of the complementary confinement scenario.

hep-lat↗
arXiv2006

$Z_6$ symmetry, electroweak transition, and magnetic monopoles at high temperature

We consider the lattice realization of the Standard Model with an additional $Z_6$ symmetry. Numerical simulations were performed on the asymmetric lattice, which corresponds to the finite temperature theory. Our choice of parameters corresponds to large Higgs masses ($M_H > 90$ Gev). The phase diagram was investigated and has been found to be different from that of the usual lattice realization of the Standard Model. It has been found, that the confinement-deconfinement phase transition lines for the SU(2) and SU(3) fields coincide. The transition line between Higgs and symmetric deconfinement parts of the phase diagram and the confinement-deconfinement transition line meet in a triple point. The transition between Higgs and symmetric parts of the phase diagram corresponds to the finite temperature electroweak transition/crossover. We see for the first time evidence that Nambu monopoles are condensed at $T>T_c$ while at $T<T_c$ their condensate vanishes.

hep-lat↗
arXiv2006

Inclusive pentaquark and strange baryons production in pp and Σp collisions at high energy

We calculate the cross sections for the inclusive production in the fragmentation region of $Θ^+(1540)$ and $Λ(1520)$ in $pp$ collisions and $Λ(1520)$ in $Σp$ collisions at high energy using the $K$- and $π$-meson exchange diagrams, respectively. The contributions of these diagrams survive at asymptotically large energies and are energy independent in this region up to logarithmic and power corrections. We find that inclusive $Θ^+(1540)$ production should be at the level of 1 $μ\mathrm{b}\timesΓ_{ΘKN}/ 1$ MeV. The ratio of the $Θ^+(1540)$ over the $Λ(1520)$ yields is found to be $\sim 1%$. The fraction of $Λ(1520)$ yields in $Σp$ and $pp$ collisions is $\sim 2.7$ that quantitatively agrees with the preliminary result of the Fermilab fixed target experiment E781.

hep-ph↗
arXiv2006

Calorons and monopoles from smeared SU(2) lattice fields at non-zero temperature

In equilibrium, at finite temperature below and above the deconfining phase transition, we have generated lattice SU(2) gauge fields and have exposed them to smearing in order to investigate the emerging clusters of topological charge. Analysing in addition the monopole clusters according to the maximally Abelian gauge, we have been able to characterize part of the topological clusters to correspond either to non-static calorons or static dyons in the context of Kraan-van Baal caloron solutions with non-trivial holonomy. We show that the relative abundance of these calorons and dyons is changing with temperature and offer an interpretation as dissociation of calorons into dyons with increasing temperature. The profile of the Polyakov loop inside the topological clusters and the (model-dependent) accumulated topological cluster charges support this interpretation. Above the deconfining phase transition light dyons (according to Kraan-van Baal caloron solutions with almost trivial holonomy) become the most abundant topological objects. They are presumably responsible for the magnetic confinement in the deconfined phase.

hep-lat↗
arXiv2005

Dynamics of quark-gluon plasma from Field correlators

It is argued that strong dynamics in the quark-gluon plasma and bound states of quarks and gluons is mostly due to nonperturbative effects described by field correlators. The emphasis in the paper is made on two explicit calculations of these effects from the first principles: one analytic using gluelump Green's functions and another using independent lattice data on correlators. The resulting hadron spectra are investigated in the range T_c < T < 2T_c. The spectra of charmonia, bottomonia, light s-sbar mesons, glueballs and quark-gluon states calculated numerically are in general agreement with lattice MEM data. The possible role of these bound states in the thermodynamics of quark-gluon plasma is discussed.

hep-ph↗
arXiv2005

Standard Model with the additional $Z_6$ symmetry on the lattice

An additional $Z_6$ symmetry hidden in the fermion and Higgs sectors of the Standard Model has been found recently\cite{BVZ2003}. A lattice regularization of the Standard Model was constructed that possesses this symmetry. In \cite{BVZ2004} we have reported our results on the numerical simulation of the Electroweak sector of the model. In this paper we report our results on the numerical simulation of the full ($SU(3)\otimes SU(2) \otimes U(1)$) model. The phase diagram of the model has been investigated using static quark and lepton potentials. Various types of monopoles have been constructed. Their densities appear to be sensitive to the phase transition lines. Differences between the realizations of the Standard Model which do or do not possess the mentioned $Z_6$ symmetry, are discussed.

hep-lat↗
arXiv2005

The monopole content of topological clusters : have KvB calorons been found?

Using smearing of equilibrium lattice fields generated at finite temperature in the confined phase of SU(2) lattice gauge theory, we have investigated the emerging topological objects (clusters of topological charge). Analysing their monopole content according to the Polyakov gauge and the maximally Abelian gauge, we characterize part of them to correspond to nonstatic calorons or static dyons in the context of Kraan-van Baal caloron solutions with non-trivial holonomy. The behaviour of the Polyakov loop inside these clusters and the (model-dependent) topological charges of these objects support this interpretation.

hep-lat↗
arXiv2004

Leptonic widths of high excitations in heavy quarkonia

Agreement with the measured electronic widths of the $ψ(4040)$, $ψ(4415)$, and $Υ(11019)$ resonances is shown to be reached if two effects are taken into account: a flattening of the confining potential at large distances and a total screening of the gluon-exchange interaction at $r\ga 1.2$ fm. The leptonic widths of the unobserved $Υ(7S)$ and $ψ(5S)$ resonances: $Γ_{e^+e^-}(Υ(7S))=0.11$ keV and $Γ(ψ(5S))\approx 0.54$ keV are predicted.

hep-ph↗
arXiv2004

The heavy-quark pole masses in the Hamiltonian approach

From the fact that the nonperturbative self-energy contribution $C_{\rm SE}$ to the heavy meson mass is small: $C_{\rm SE}(b\bar{b})=0$; $C_{\rm SE}(c\bar{c})\cong -40$ MeV \cite{ref.01}, strong restrictions on the pole masses $m_b$ and $m_c$ are obtained. The analysis of the $b\bar{b}$ and the $c\bar{c}$ spectra with the use of relativistic (string) Hamiltonian gives $m_b$(2-loop)$=4.78\pm 0.05$ GeV and $m_c$(2-loop)$=1.39 \pm 0.06$ GeV which correspond to the $\bar{\rm MS}$ running mass $\bar{m}_b(\bar{m}_b)=4.19\pm 0.04$ GeV and $\bar{m}_c(\bar{m}_c)=1.10\pm 0.05$ GeV. The masses $ω_c$ and $ω_b$, which define the heavy quarkonia spin structure, are shown to be by $\sim 200$ MeV larger than the pole ones.

hep-ph↗
arXiv2004

The static force in background perturbation theory

The static force $F_B(r)$ and the strong coupling $α_F(r)$, which defines the gluon-exchange part of $F_B(r)$, are studied in QCD background perturbation theory (BPT). In the region $r\la 0.6 $ fm $α_F(r)$ turns out to be essentially smaller than the coupling $α_B(r)$ in the static potential. For the dimensionless function $Φ_B(r) = r^2 F_B(r)$ the characteristic values $Φ_B(r_1) =1.0$ and $Φ_B(r_0)=1.65$ are shown to be reached at the following $Q\bar Q$ separations: $r_1\sqrtσ =0.77, r_0\sqrtσ =1.09$ in quenched approximation and $r_1\sqrtσ=0.72, r_0\sqrtσ=1.04$ for $n_f =3$. The numbers obtained appear to be by only 8% smaller than those calculated in lattice QCD while the values of the couplings $α_F(r_1)$ and $α_F(r_0)$ in BPT are by $\sim 30% (n_f =3)$ and $50% (n_f=0)$ larger than corresponding lattice couplings. With the use of the BPT potential good description of the bottomonium spectrum is obtained.

hep-ph↗