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M. Ruggieri

Publications and source records attributed to M. Ruggieri.

47 records · Page 3Linked to original sources
arXiv2006

Effect of neutrino trapping on the three flavor FFLO phase of QCD

We compute the effect of a non-zero lepton chemical potential on the structure of the three flavor Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase of QCD at finite temperature. We show that, as in the BCS case, the lepton chemical potential favors two-species color superconductivity and disfavors the three species pairing. We stress that this study could be relevant for the cooling of a proto-neutron star with a FFLO core, if the temperatures are higher than the un-trapping temperature.

hep-ph↗
arXiv2006

Ginzburg-Landau approach to the three flavor LOFF phase of QCD

We explore, using a Ginzburg-Landau expansion of the free energy, the Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase of QCD with three flavors, using the NJL four-fermion coupling to mimic gluon interactions. We find that, below the point where the QCD homogeneous superconductive phases should give way to the normal phase, Cooper condensation of the pairs u-s and d-u is possible, but in the form of the inhomogeneous LOFF pairing.

hep-ph↗
arXiv2005

Smeared gap equations in crystalline color superconductivity

In the framework of HDET, we discuss an averaging procedure of the NJL quark-quark interaction lagrangian, treated in the mean field approximation, for the two flavor LOFF phase of QCD. This procedure gives results which are valid in domains where Ginzburg-Landau results may be questionable. We compute and compare the free energy for different LOFF crystalline structures.

hep-ph↗
arXiv2005

Meissner masses in the gCFL phase of QCD

We calculate the Meissner masses of gluons in neutral three-flavor color superconducting matter for finite strange quark mass. In the CFL phase the eissner masses are slowly varying function of the strange quark mass. For large strange quark mass, in the so called gCFL phase, the Meissner masses of gluons with colors $a=1,2,3$ and 8 become imaginary, indicating an instability.

hep-ph↗
arXiv2004

Magnetic properties of the Larkin-Ovchinnikov-Fulde-Ferrell superconducting phase

We compute, at the first order in the fine structure constant, the parameters of the electromagnetic Lagrangian for the inhomogeneous Larkin-Ovchinnikov-Fulde-Ferrell phase in Quantum Chromodynamics (QCD) and in condensed matter. In particular we compute for QCD with two flavors the dielectric and the magnetic permeability tensors, and for condensed matter superconductors the penetration depth of external magnetic fields.

hep-ph↗
arXiv2004

Effective Gap Equation for the Inhomogeneous LOFF Superconductive Phase

We present an approximate gap equation for different crystalline structures of the LOFF phase of high density QCD at T=0. This equation is derived by using an effective condensate term obtained by averaging the inhomogeneous condensate over distances of the order of the crystal lattice size. The approximation is expected to work better far off any second order phase transition. As a function of the difference of the chemical potentials of the up and down quarks, $δμ$, we get that the octahedron is energetically favored from $δμ=Δ_0/\sqrt 2$ to $0.95Δ_0$, where $Δ_0$ is the gap for the homogeneous phase, while in the range $0.95Δ_0-1.32Δ_0$ the face centered cube prevails. At $δμ=1.32Δ_0$ a first order phase transition to the normal phase occurs.

hep-ph↗
arXiv2003

Quasi-particle Specific Heats for the Crystalline Color Superconducting Phase of QCD

We calculate the specific heats of quasi-particles of two-flavor QCD in its crystalline phases for low temperature. We show that for the different crystalline structures considered here there are gapless modes contributing linearly in temperature to the specific heat. We evaluate also the phonon contributions which are cubic in temperature. These features might be relevant for compact stars with an inner shell in a color superconducting crystalline phase.

hep-ph↗
arXiv2003

High density effective theory results for two and three massive flavors color-suoerconductivity

We describe some topics related to massive two and three flavors color superconductivity (CSC), obtained in the framework of high density effective theory (HDET); moreover we present a {\em modified} Nambu-Jona Lasinio model with running - as opposite to fixed - ultraviolet cutoff, discussing the troubles that one encounters with the former when discussing QCD at high density.

hep-ph↗
arXiv2003

Aspects of the Color Flavor Locking phase of QCD in the Nambu-Jona Lasinio approximation

We study two aspects of the CFL phase of QCD in the NJL approximation. The first one is the issue of the dependence on μof the ultraviolet cutoff in the gap equation, which is solved allowing a running coupling constant. The second one is the dependence of the gap on the strange quark mass; using the high density effective theory we perform an expansion in the parameter (m_s/μ)^2 after checking that its numerical validity is very good already at first order.

hep-ph↗
arXiv2002

Massive quark effects in two flavor color superconductors

The high density effective theory formalism (HDET) is employed to describe high density QCD with two massive flavors (2SC). The gap equation is derived and explicitly solved for the gap parameter. The parameters associated to the pseudo Nambu-Goldstone boson of $U(1)_A$ are evaluated in the limit $μ\to\infty$ and $m/μ$ fixed. In particular we find for the velocity of the NG boson the relation $v^2=\sqrt{μ_1^2-m_1^2}\sqrt{μ_2^2-m_2^2}/3μ_1μ_2$.

hep-ph↗