Galilean limit of equilibrium relativistic mass distribution for indistinguishable events

The relativistic distribution for indistinguishable events is considered in the mass-shell limit $m^2\cong M^2,$ where $M$ is a given intrinsic property of the events. The characteristic thermodynamic quantities are calculated and subject to the zero-mass and the high-temperature limits. The results are shown to be in agreement with the corresponding expressions of an on-mass-shell relativistic kinetic theory. The Galilean limit $c\rightarrow \infty ,$ which coincides in form with the low-temperature limit, is considered. The theory is shown to pass over to a nonrelativistic statistical mechanics of indistinguishable particles.Comment: Report TAUP-2136-9

Now so near, and yet still so far: economic relations between Ukraine and the European Union

Kiev is not so far away from Brussels as one might expect. Ukraine already performs quite well when compared to the other countries in the queue for entry into the EU. Especially the fiscal and external debt figures are better than in other countries. On the negative side, there is a considerable backlog with respect to the development of administrative and judicial institutional capacities, and a potential for macroeconomic instability due to monetary expansion, rising inflation rates, and real exchange rate instability. From a macro perspective, the most pressing issue is to end inflationary pressures resulting from targeting the exchange rate to a weakening dollar. Among the alternative frameworks available to Ukraine, the current exchange rate anchor can be made more flexible by targeting a basket made of the US dollar and the euro. Such an exchange rate anchor framework provides a clear indication to the public about monetary policy, disciplines fiscal policy, and is relatively easy to manage. Additionally, a clearer link to the euro may be useful for a greater integration into the EU. From a micro perspective, the most pressing issues which can be targeted in the short run are taxation and competition policy. The tax system is unstable, complex, and inconsistent. A reduction of tax exemptions could broaden the tax base and allow for lower nominal tax rates. Privatization has been rather limited in the non-traded goods sectors. Additionally, the completion of privatization needs to be coupled with a more robust and consistent regulatory framework in order to attract more FDI, as was the case in the new member states of the EU. Sandwiched between the EU and Russia, Ukraine is likely to derive substantial gains from EU integration. Excluding the energy sector reveals that Ukrainian trade with the EU already outperforms its trade with Russia. In addition, EU integration is likely to attract more inflows of foreign capital if the new government is able to provide a more attractive macroeconomic and institutional environment. Ukraine should press for fast reforms and use the ?honeymoon? period of the new government to open negotiations for EU membership by submitting a formal application. This will, among other things, help to prevent vested interest groups from blocking the reform process. A pragmatic approach for an integration strategy would include four elements: identifying reform priorities; harmonizing Ukraine?s legislation with EU law; undertaking steps to get a market economy status from the EU; and, finally, signing a free trade agreement with the EU. The EU, on its side, should actively support the continuation of the reform process in the country, especially with respect to institution building. Finally, one must stress that the EU itself will gain from this enlargement, as it has gained from all the previous ones. In our view both sides are now facing a historic opportunity that should not be missed, neither by Kiev nor by Brussels. --

A New Relativistic High Temperature Bose-Einstein Condensation

We discuss the properties of an ideal relativistic gas of events possessing Bose-Einstein statistics. We find that the mass spectrum of such a system is bounded by $\mu \leq m\leq 2M/\mu _K,$ where $\mu$ is the usual chemical potential, $M$ is an intrinsic dimensional scale parameter for the motion of an event in space-time, and $\mu _K$ is an additional mass potential of the ensemble. For the system including both particles and antiparticles, with nonzero chemical potential $\mu ,$ the mass spectrum is shown to be bounded by $|\mu |\leq m\leq 2M/\mu _K,$ and a special type of high-temperature Bose-Einstein condensation can occur. We study this Bose-Einstein condensation, and show that it corresponds to a phase transition from the sector of continuous relativistic mass distributions to a sector in which the boson mass distribution becomes sharp at a definite mass $M/\mu _K.$ This phenomenon provides a mechanism for the mass distribution of the particles to be sharp at some definite value.Comment: Latex, 22 page

Now so near, and yet still so far: economic relations between Ukraine and the European Union

Kiev is not so far away from Brussels as one might expect. Ukraine already performs quite well when compared to the other countries in the queue for entry into the EU. Especially the fiscal and external debt figures are better than in other countries. On the negative side, there is a considerable backlog with respect to the development of administrative and judicial institutional capacities, and a potential for macroeconomic instability due to monetary expansion, rising inflation rates, and real exchange rate instability. From a macro perspective, the most pressing issue is to end inflationary pressures resulting from targeting the exchange rate to a weakening dollar. Among the alternative frameworks available to Ukraine, the current exchange rate anchor can be made more flexible by targeting a basket made of the US dollar and the euro. Such an exchange rate anchor framework provides a clear indication to the public about monetary policy, disciplines fiscal policy, and is relatively easy to manage. Additionally, a clearer link to the euro may be useful for a greater integration into the EU. From a micro perspective, the most pressing issues which can be targeted in the short run are taxation and competition policy. The tax system is unstable, complex, and inconsistent. A reduction of tax exemptions could broaden the tax base and allow for lower nominal tax rates. Privatization has been rather limited in the non-traded goods sectors. Additionally, the completion of privatization needs to be coupled with a more robust and consistent regulatory framework in order to attract more FDI, as was the case in the new member states of the EU. Sandwiched between the EU and Russia, Ukraine is likely to derive substantial gains from EU integration. Excluding the energy sector reveals that Ukrainian trade with the EU already outperforms its trade with Russia. In addition, EU integration is likely to attract more inflows of foreign capital if the new government is able to provide a more attractive macroeconomic and institutional environment. Ukraine should press for fast reforms and use the ?honeymoon? period of the new government to open negotiations for EU membership by submitting a formal application. This will, among other things, help to prevent vested interest groups from blocking the reform process. A pragmatic approach for an integration strategy would include four elements: identifying reform priorities; harmonizing Ukraine?s legislation with EU law; undertaking steps to get a market economy status from the EU; and, finally, signing a free trade agreement with the EU. The EU, on its side, should actively support the continuation of the reform process in the country, especially with respect to institution building. Finally, one must stress that the EU itself will gain from this enlargement, as it has gained from all the previous ones. In our view both sides are now facing a historic opportunity that should not be missed, neither by Kiev nor by Brussels

Thermodynamics of Hidden Sector Gaugino Condensation in the Expanding Universe

This work examines the confining-deconfining phase transition in a hidden Yang Mills sector with scale $\Lambda \sim 10^{14}$ GeV appropriate to dilaton stabilization and SUSY-breaking via formation of a gaugino consensate. If the transition is assumed to take place through homogenous nucleation, then under reasonable assumptions it is found that a critical bubble, formed at a temperature which provides enough supercooling, is not large enough to accommodate an adequate number (\gsim 100) of quanta of the confined phase (`hidden hadrons') to allow a consistent thermodynamic description. Thus, a first order transition in the hidden sector may not be possible in the expanding universe.Comment: 13 pages LaTex, no figure

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.Comment: 5 pages, 5 figures, accepted in Physical Review Letter

Regge Trajectories for Mesons in the Holographic Dual of Large-N_c QCD

We discuss Regge trajectories of dynamical mesons in large-N_c QCD, using the supergravity background describing N_c D4-branes compactified on a thermal circle. The flavor degrees of freedom arise from the addition of N_f<<N_c D6 probe branes. Our work provides a string theoretical derivation, via the gauge/string correspondence, of a phenomenological model describing the meson as rotating point-like massive particles connected by a flux string. The massive endpoints induce nonlinearities for the Regge trajectory. For light quarks the Regge trajectories of mesons are essentially linear. For massive quarks our trajectories qualitatively capture the nonlinearity detected in lattice calculations.Comment: 21 pages, 4 figures. v2: typos corrected, references and acknowledgments adde

On the Mixing of the Scalar Mesons f0(1370)f_0(1370), f0(1500)f_0(1500) and f0(1710)f_0(1710)

Based on a $3\times3$ mass matrix describing the mixing of the scalar states $f_0(1370)$, $f_0(1500)$ and $f_0(1710)$, the hadronic decays of the three states are investigated. Taking into account the two possible assumptions concerning the mass level order of the bare states $|N>=|u\bar{u}+d\bar{d}>/\sqrt{2}$, $|S>=|s\bar{s}>$ and $|G>=|gg>$ in the scalar sector, $M_G > M_S > M_N$ and $M_G > M_N > M_S$, we obtain the glueball-quarkonia content of the three states by solving the unlinear equations. Some predictions about the decays of the three states in two cases are presented, which can provide a stringent consistency check of the two assumptions.Comment: revtex 10 pages, 1 eps figur

Bohr-Sommerfeld quantization and meson spectroscopy

We use the Bohr-Sommerfeld quantization approach in the context of constituent quark models. This method provides, for the Cornell potential, analytical formulae for the energy spectra which closely approximate numerical exact calculations performed with the Schrodinger or the spinless Salpeter equations. The Bohr-Sommerfeld quantization procedure can also be used to calculate other observables such as r.m.s. radius or wave function at the origin. Asymptotic dependence of these observables on quantum numbers are also obtained in the case of potentials which behave asymptotically as a power-law. We discuss the constraints imposed by these formulae on the dynamics of the quark-antiquark interaction.Comment: 13 page

Relativistic Brownian Motion

Stimulated by experimental progress in high energy physics and astrophysics, the unification of relativistic and stochastic concepts has re-attracted considerable interest during the past decade. Focusing on the framework of special relativity, we review, here, recent progress in the phenomenological description of relativistic diffusion processes. After a brief historical overview, we will summarize basic concepts from the Langevin theory of nonrelativistic Brownian motions and discuss relevant aspects of relativistic equilibrium thermostatistics. The introductory parts are followed by a detailed discussion of relativistic Langevin equations in phase space. We address the choice of time parameters, discretization rules, relativistic fluctuation-dissipation theorems, and Lorentz transformations of stochastic differential equations. The general theory is illustrated through analytical and numerical results for the diffusion of free relativistic Brownian particles. Subsequently, we discuss how Langevin-type equations can be obtained as approximations to microscopic models. The final part of the article is dedicated to relativistic diffusion processes in Minkowski spacetime. Due to the finiteness of velocities in relativity, nontrivial relativistic Markov processes in spacetime do not exist; i.e., relativistic generalizations of the nonrelativistic diffusion equation and its Gaussian solutions must necessarily be non-Markovian. We compare different proposals that were made in the literature and discuss their respective benefits and drawbacks. The review concludes with a summary of open questions, which may serve as a starting point for future investigations and extensions of the theory.Comment: review article, 159 pages, references updated, misprints corrected, App. A.4. correcte