Stability of color-flavor locked strangelets

The stability of color-flavor locked (CFL) strangelets is studied in the three-flavor Nambu--Jona-Lasinio model. We consider all quark flavors to be massless, for simplicity. By making use of the multiple reflection expansion, we explicitly take into account finite size effects and formulate the thermodynamic potential for CFL strangelets. We find that the CFL gap could be large enough so that the energy per baryon number of CFL strangelets is greatly affected. In addition, if the quark-quark coupling constant is larger than a certain critical value, there is a possibility of finding absolutely stable CFL strangelets.Comment: 7 pages, 3 figures, to appear in Int. J. Mod. Phys.

Latent heat in the chiral phase transition

The chiral phase transition at finite temperature and density is discussed in the framework of the QCD-like gauge field theory. The thermodynamical potential is investigated using a variational approach. Latent heat generated in the first-order phase transition is calculated. It is found that the latent heat is enhanced near the tricritical point and is more than several hundred MeV per quark.Comment: 6 pages, 3 figure

Effective potential for composite operators and for an auxiliary scalar field in a Nambu-Jona-Lasinio model

We derive the effective potentials for composite operators in a Nambu-Jona-Lasinio (NJL) model at zero and finite temperature and show that in each case they are equivalent to the corresponding effective potentials based on an auxiliary scalar field. The both effective potentials could lead to the same possible spontaneous breaking and restoration of symmetries including chiral symmetry if the momentum cutoff in the loop integrals is large enough, and can be transformed to each other when the Schwinger-Dyson (SD) equation of the dynamical fermion mass from the fermion-antifermion vacuum (or thermal) condensates is used. The results also generally indicate that two effective potentials with the same single order parameter but rather different mathematical expressions can still be considered physically equivalent if the SD equation corresponding to the extreme value conditions of the two potentials have the same form.Comment: 7 pages, no figur

QCD Critical Points and Their Associated Soft Modes

The mean-field level calculation shows that the QCD matter can have multiple critical points incorporating the color superconductivity under charge neutrality constraint due to the repulsive vector interaction; this actually implies that the QCD matter is very soft for a simultaneous formation of diquark and chiral condensates coupled with the baryonic density. Dynamical density fluctuations are analyzed as possible soft modes around the QCD critical point using dissipative relativistic fluid dynamics. It is found that the entropy fluctuation solely gets enhanced while the sound modes due to mechanical density fluctuations are strongly attenuated around the QCD CP, which may suggest a suppression or even total disappearance of Mach cone at the CP.Comment: 8 pages, 3 figures. Talk presented at Yukawa International workshop "New Frontiers in QCD 2010 --- Exotic Hadron Systems and Dense Matter ---" (NFQCD10), Jan. 18(Mon.)-Mar.19(Fri), 2010, Yukawa Institute for Theoretical Physics, Kyoto, Japa

Chiral phase transition at high temperature in the QCD-like gauge theory

The chiral phase transition at high temperature is investigated using the effect ive potential in the framework of the QCD-like gauge theory with a variational a pproach. We have a second order phase transition at $T_c=136$MeV. We also investigate numerically the temperature dependence of condensate, $f_\pi$ a nd $a_2(T)$(coefficient of the quadratic term in the effective potential) and es timate the critical exponents of these quantities.Comment: 12 pages,7 figure

Current quark mass effects on chiral phase transition of QCD in the improved ladder approximation

Current quark mass effects on the chiral phase transition of QCD is studied in the improved ladder approximation. An infrared behavior of the gluon propagator is modified in terms of an effective running coupling. The analysis is based on a composite operator formalism and a variational approach. We use the Schwinger-Dyson equation to give a ``normalization condition'' for the Cornwall-Jackiw-Tomboulis effective potential and to isolate the ultraviolet divergence which appears in an expression for the quark-antiquark condensate. We study the current quark mass effects on the order parameter at zero temperature and density. We then calculate the effective potential at finite temperature and density and investigate the current quark mass effects on the chiral phase transition. We find a smooth crossover for $T>0$, $\mu=0$ and a first-order phase transition for $\mu>0$, T=0. Critical exponents are also studied and our model gives the classical mean-field values. We also study the temperature dependence of masses of scalar and pseudoscalar bosons. A critical end point in the $T$-$\mu$ plane is found at $T \sim 100$ MeV, $\mu \sim 300$ MeV.Comment: 19 pages, 13 figure

Soft X-ray harmonic comb from relativistic electron spikes

We demonstrate a new high-order harmonic generation mechanism reaching the `water window' spectral region in experiments with multi-terawatt femtosecond lasers irradiating gas jets. A few hundred harmonic orders are resolved, giving uJ/sr pulses. Harmonics are collectively emitted by an oscillating electron spike formed at the joint of the boundaries of a cavity and bow wave created by a relativistically self-focusing laser in underdense plasma. The spike sharpness and stability are explained by catastrophe theory. The mechanism is corroborated by particle-in-cell simulations

Observation of Burst Intensification by Singularity Emitting Radiation generated from relativistic plasma with a high-intensity laser

Coherent x-rays via the Burst Intensification by Singularity Emitting Radiation (BISER) mechanism are generated from relativistic plasma in helium gas target. A broad modulation of the BISER spectrum, which is significantly wider than the harmonic order, is observed and characterized. In particular, we found that the modulation period can be as large as 41 eV