Obama and Medvedev – Improving US-Russian relations

After Dmitry Medvedev delivered his message to the Federation Council here last week, news outlets in the U.S. and Britain jumped on the Russian president’s seemingly hostile rhetoric regarding the planned missile defense system to be placed in Poland and the Czech Republic. Russia, Medvedev said, would respond by planting a system in Kaliningrad, on the Baltic Sea. The New York Times, which accompanied its coverage with a photo of troops on parade in Red Square, focused on his harsh words as well as the fact that that he did not congratulate Barack Obama on his election victory

D mesons at finite temperature and density in the PNJL model

We study D meson resonances in hot, dense quark matter within the NJL model and its Polyakov-loop extension. We show that the mass splitting between D^+ and D^- mesons is moderate, not in excess of 100 MeV. When the decay channel into quasifree quarks opens (Mott effect) at densities above twice saturation density, the decay width reaches rapidly the value of 200 MeV which entails a spectral broadening sufficient to open J/psi dissociation processes. Contrary to results from hadronic mean-field theories, the chiral quark model does not support the scenario of a dropping D meson masses so that scenarios for J/psi dissociation by quark rearrangement built on the lowering of the threshold for this process in a hot and dense medium have to be reconsidered and should account for the spectral broadening.Comment: 7 pages, 7 figures, references, text and figure 1 adde

η−η′\eta - \eta' in a hot and dense medium

The behavior of $\eta$ and $\eta'$ in hot strange quark matter in weak equilibrium with temperature, is investigated within the SU(3) Nambu-Jona-Lasinio [NJL] model. Possible manifestations of restoration of symmetries, by temperature or density, in the behavior of $\eta$ and $\eta'$ are discussed. The role played by the combined effect of temperature and density in the nature of the phase transition and meson behavior is also analyzed.Comment: 15 pages, 5 figures. Contribution to the Second International Workshop on Hadron Physics, Effective Theories of Low Energy QCD, 25-29 September, 2002 (Coimbra, Portugal

Bilocal Field Approach and Semileptonic Heavy Meson Decays

In this paper we consider the bilocal field approach for $QCD$. We obtain a bilocal effective meson action with a potential kernel given in relativistic covariant form. The corresponding Schwinger--Dyson and Bethe--Salpeter equations are investigated in detail. By introducing weak interactions into the theory we study heavy meson properties as decay constants and semileptonic decay amplitudes. Thereby, the transition from the bilocal field description to the heavy quark effective theory is discussed. Considering as example the semileptonic decay of a pseudoscalar $B$--meson into a pseudoscalar $D$--meson we obtain an integral expression for the corresponding Isgur--Wise function in terms of meson wave functions.Comment: 27 pages and 2 figures (available upon request), DESY 92-07

A long goodbye

What Gorbachev’s effort to get out of Afghanistan can tell us about how a President Obama might face the challenge of withdrawing from Iraq

Afghanistan: more echoes of the Soviet experience

Over at Slate, Frank Kaplan writes that NATO forces in Afghanistan are starting to shift their focus from the state-building aspects of COIN to more traditional military operations. Not that the state building effort is dead, writes Kaplan, but “U.S. and NATO officers, intelligence analysts, and other officials and advisers now believe that our objectives in the Afghanistan war can no longer be accomplished in sufficiently short time through COIN alone or even through a COIN-dominant strategy.