36 research outputs found
Galilean limit of equilibrium relativistic mass distribution for indistinguishable events
The relativistic distribution for indistinguishable events is considered in
the mass-shell limit where 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 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 where is the usual chemical
potential, is an intrinsic dimensional scale parameter for the motion of an
event in space-time, and is an additional mass potential of the
ensemble. For the system including both particles and antiparticles, with
nonzero chemical potential the mass spectrum is shown to be bounded by
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 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 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 , and
Based on a mass matrix describing the mixing of the scalar states
, and , 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
, and in the
scalar sector, and , 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