arXiv subjects

L. Burakovsky

Publications and source records attributed to L. Burakovsky.

At least 19 recordsLinked to original sources

arXiv2019

Exploring the behavior of vanadium under high-pressure and high-temperature conditions

We report a combined experimental and theoretical study of the melting curve and the structural behavior of vanadium under extreme pressure and temperature. We performed powder x-ray diffraction experiments up to 120 GPa and 4000 K, determining the phase boundary of the bcc-to-rhombohedral transition and melting temperatures at different pressures. Melting temperatures have also been established from the observation of temperature plateaus during laser heating, and the results from the density-functional theory calculations. Results obtained from our experiments and calculations are fully consistent and lead to an accurate determination of the melting curve of vanadium. These results are discussed in comparison with previous studies. The melting temperatures determined in this study are higher than those previously obtained using the speckle method, but also considerably lower than those obtained from shock-wave experiments and linear muffin-tin orbital calculations. Finally, a high-pressure high-temperature equation of state up to 120 GPa and 2800 K has also been determined.

cond-mat.mtrl-sci↗

arXiv2018

High-pressure high-temperature phase diagram of zinc

The phase diagram of Zn has been explored up to 140 GPa and 6000 K, by combining optical observations, x-ray diffraction, and ab-initio calculations. In the pressure range covered by this study, Zn is found to retain a hexagonal close-packed crystal symmetry up to the melting temperature. The known decrease of the axial ratio of the hcp phase of Zn under compression is observed in x-ray diffraction experiments from 300 K up to the melting temperature. The pressure at which the axial ratio reaches the square root of 3 value, around 10 GPa, is slightly affected by temperature. When this axial ratio is reached, we observed that single crystals of Zn, formed at high temperature, break into multiple polycrystals. In addition, a noticeable change in the pressure dependence of the axial ratio takes place at the same pressure. Both phenomena could be caused by an isomorphic second-order phase transition induced by pressure in Zn. The reported melt curve extends previous results from 24 to 135 GPa. The pressure dependence obtained for the melting temperature is accurately described up to 135 GPa by using a Simon-Glatzel equation. The determined melt curve agrees with previous low-pressure studies and with shock-wave experiments, with a melting temperature of 5060 K at 135 GPa. Finally, a thermal equation of state is reported, which at room-temperature agrees with the literature.

cond-mat.mtrl-sci↗

arXiv2003

Nonlinear Regge trajectories and glueballs

We apply a phenomenological approach based on nonlinear Regge trajectories to glueball states. The parameters, i.e., intercept and threshold, or trajectory termination point beyond which no bound states should exist, are determined from pomeron (scattering) data. Systematic errors inherent to the approach are discussed. We then predict masses of glueballs on the tensor trajectory. For comparison, the approach is applied to available quenched lattice data. We find a discrepancy between the lattice based thresholds and the pomeron threshold that we extract from data.

nucl-th↗

arXiv2003

Dislocation lines as the precursor of the melting of crystalline solids observed in Monte Carlo simulations

The microscopic mechanism of the melting of a crystal is analyzed by the constant pressure Monte Carlo simulation of a Lennard-Jones fcc system. Beyond a temperature of the order of 0.8 of the melting temperature, we found that the relevant excitations are lines of defects. Each of these lines has the structure of a random walk of various lengths on an fcc defect lattice. We identify these lines with the dislocation ones proposed in recent phenomenological theories of melting. Near melting we find the appearance of long lines that cross the whole system. We suggest that these long lines are the precursor of the melting process.

cond-mat.mtrl-sci↗

arXiv2002

An analytic model of the shear modulus at all densities and temperatures

An analytic model of the shear modulus applicable at temperatures up to melt and at all densities is presented. It is based in part on a relation between the melting temperature and the shear modulus at melt. Experimental data on argon are shown to agree with this relation to within 1%. The model of the shear modulus involves seven parameters, all of which can be determined from zero-pressure experimental data. We obtain the values of these parameters for 11 elemental solids. Both the experimental data on the room-temperature shear modulus of argon to compressions of \sim 2.5, and theoretical calculations of the zero-temperature shear modulus of aluminum to compressions of \sim 3.5 are in good agreement with the model. Electronic structure calculations of the shear moduli of copper and gold to compressions of 2, performed by us, agree with the model to within uncertainties.

cond-mat↗

arXiv2002

An analytic model of the Gruneisen parameter at all densities

We model the density dependence of the Gruneisen parameter as gamma(rho) = 1/2 + gamma_1/rho^{1/3} + gamma_2/rho^{q}, where gamma_1, gamma_2, and q>1 are constants. This form is based on the assumption that gamma is an analytic function of V^{1/3}, and was designed to accurately represent the experimentally determined low-pressure behavior of gamma. The numerical values of the constants are obtained for 20 elemental solids. Using the Lindemann criterion with our model for gamma, we calculate the melting curves for Al, Ar, Ni, Pd, and Pt and compare them to available experimental melt data. We also determine the Z (atomic number) dependence of gamma_1. The high-compression limit of the model is shown to follow from a generalization of the Slater, Dugdale-MacDonald, and Vashchenko-Zubarev forms for the dependence of the Gruneisen parameter.

cond-mat↗

arXiv2000

Spectroscopy "windows" of quark-antiquark mesons and glueballs with effective Regge trajectories

Regge trajectories of quark-antiquark mesons can be well approximated for phenomenology purposes by a specific nonlinear form, reflecting that the flux tubes cannot be arbitrarily large, but break due to the effect of pair-production. If confirmed, this would imply that there is only a finite number of bound states on each trajectory, and consequently, an existence of ``spectroscopy windows'' for each flavor. Here we present our results for these windows.

hep-ph↗

arXiv2000

Lessons from Hadron Phenomenology

Meson spectra can be well approximated by a specific form of a nonlinear Regge trajectory which is consistent with a finite number of bound states. This may have important consequencies for experiment, and may be a hint for the theory.

hep-ph↗

arXiv2000

Effective Functional Form of Regge Trajectories

We present theoretical arguments and strong phenomenological evidence that hadronic Regge trajectories are essentially nonlinear and can be well approximated, for phenomenological purposes, by a specific square-root form.

hep-ph↗

arXiv1999

Effect of Color Screening on Heavy Quarkonia Regge Trajectories

Using an unquenched lattice potential to calculate the spectrum of the bottomonium system, we demonstrate numerically that the effect of pair creation is to produce termination of hadronic Regge trajectories, in contrast to the Veneziano model and the vast majority of phenomenological generalizations. Termination of Regge trajectories may have significant experimental consequences.

hep-ph↗

arXiv1999

String Model for Analytic Nonlinear Regge Trajectories

We present a new generalized string model for Regge trajectories J=J(E^2), where J and E are the orbital momentum and energy of the string, respectively. We demonstrate that this model is not to produce linear Regge trajectories, in contrast to the standard Nambu-Goto string, but generally nonlinear trajectories, which in many cases can be given in analytic form. As an example, we show how the model generates square-root, logarithmic and hyperbolic trajectories that have been discussed in the literature.

hep-ph↗

arXiv1998

New Mass and Mass-Mixing Angle Relations for Pseudoscalar Mesons

We study the origins of the inaccuracies of Schwinger's nonet mass, and the Sakurai mass-mixing angle, formulae for the pseudoscalar meson nonet, and suggest new versions of them, modified by the inclusion of the pseudoscalar decay constants. We use these new formulae to determine the pseudoscalar decay constants and mixing angle. The results obtained, $f_8/f_π= 1.185\pm 0.040,$ $f_9/f_π=1.095\pm 0.020,$ $f_η/f_π= 1.085\pm 0.025,$ $f_{η^{'}}/f_π=1.195\pm 0.035,$ $θ= (-21.4\pm 1.0)^o,$ are in excellent agreement with experiment.

hep-ph↗

arXiv1998

Comment on "Regge Trajectories for All Flavors"

We show that Regge trajectories for all flavors suggested recently by Filipponi et al. cannot combine both meson spectroscopy and additivity of intercepts. Other defects of these trajectories are also discussed.

hep-ph↗

arXiv1998

Hadron Spectroscopy in Regge Phenomenology

We show that linear Regge trajectories for mesons and baryons, and the cubic mass spectrum associated with them, determine expressions for the hadron masses in terms of the universal Regge slope α' alone. The ground state hadron masses as calculated from these expressions are in excellent agreement with experiment for α'=0.85 GeV^{-2}.

hep-ph↗

arXiv1998

Hadron Mass Scaling in Regge Phenomenology

We show that Regge phenomenology is consistent with the only universal scaling law for hadron masses, M^\ast /M=(α^{'}/α^{'\ast})^{1/2}, where asterisk indicates a finite-temperature quantity. Phenomenological models further suggest the following expression of the above scaling in terms of the temperature-dependent gluon condensate: M^\ast / M = (α^'/α^{'\ast})^{1/2} = ( ^\ast/ )^{1/4}.

hep-ph↗

arXiv1998

Glueball Spectroscopy in Regge Phenomenology

We show that linear Regge trajectories for mesons and glueballs, and the cubic mass spectrum associated with them, determine a relation between the masses of the ρmeson and the scalar glueball, M(0^{++})=3/\sqrt{2} M(ρ), which implies M(0^{++})=1620\pm 10 MeV. We also discuss relations between the masses of the scalar and tensor and 3^{--} glueballs, M(2^{++})=\sqrt{2} M(0^{++}), M(3^{--})=2M(0^{++}), which imply M(2^{++})=2290\pm 15 MeV, M(3^{++})=3240\pm 20 MeV.

hep-ph↗

arXiv1998

The Schwinger Nonet Mass and Sakurai Mass-Mixing Angle Formulae Reexamined

We study the origins of the inaccuracies of Schwinger's nonet mass, and the Sakurai mass-mixing angle, formulae for the pseudoscalar meson nonet, and suggest new versions of them, modified by the inclusion of the pseudoscalar decay constants. We use these new formulae to determine the pseudoscalar decay constants and mixing angle. The results obtained, f_8/f_π=1.185\pm 0.040, f_9/f_π=1.095\pm 0.020, f_η/f_π=1.085\pm 0.025, f_{η^{'}}/f_π=1.195\pm 0.035, θ=(-21.4\pm 1.0)^o, are in excellent agreement with experiment.

hep-ph↗

arXiv1998

New Glueball-Meson Mass Relations

Using the ``glueball dominance'' picture of the mixing between q\bar{q} mesons of different hidden flavors, we establish new glueball-meson mass relations which serve as a basis for glueball spectral systematics. For the tensor glueball mass 2.3\pm 0.1 GeV used as an input parameter, these relations predict the following glueball masses: M(0^{++})\simeq 1.65\pm 0.05 GeV, M(1^{--})\simeq 3.2\pm 0.2 GeV, M(2^{-+})\simeq 2.95\pm 0.15 GeV, M(3^{--})\simeq 2.8\pm 0.15 GeV. We briefly discuss the failure of such relations for the pseudoscalar sector. Our results are consistent with (quasi)-linear Regge trajectories for glueballs with slope \simeq 0.3\pm 0.1 GeV^{-2}.

hep-ph↗