Papers by Massimo Mannarelli
We give a pedagogical review of the properties of the various meson condensation phases triggered... more We give a pedagogical review of the properties of the various meson condensation phases triggered by a large isospin or strangeness imbalance. We argue that these phases are extremely interesting and powerful playground for exploring the properties of hadronic matter. The reason is that they are realized in a regime in which various theoretical methods overlap with increasingly precise numerical lattice QCD simulations, providing insight on the properties of color confinement and of chiral symmetry breaking.
Universe, Feb 17, 2018
Strange stars are one of the possible compact stellar objects formed in the core collapse of supe... more Strange stars are one of the possible compact stellar objects formed in the core collapse of supernovae. These hypothetical stars are made by deconfined quark matter and are selfbound. In our study, we focus on the torsional oscillations of a non bare strange star, i.e., a strange star with a thin crust made of standard nuclear matter. We construct a theoretical model assuming that the inner parts of the star are in two different phases, namely the color flavour locked phase and the crystalline colour superconducting phase. Since the latter phase is rigid, with a large shear modulus, it corresponds to a first stellar crust. Above this crust a second small crust made by standard nuclear matter is suspended thanks to a strong electromagnetic dipolar moment. We focus on the electromagnetically coupled oscillations of the two stellar crusts. Notably, we find that if a small fraction of the energy of a glitch event like a typical Vela glitch is conveyed in torsional oscillations, the small nuclear crust will likely break. This is due to the fact that in this model the maximum stress, due to torsional oscillations, is likely located near the star surface.
Journal of Physics: Conference Series
In this work we study dynamic and thermodynamic (at T = 0) properties of mesons in asymmetric mat... more In this work we study dynamic and thermodynamic (at T = 0) properties of mesons in asymmetric matter in the framework of Chiral Perturbation Theory. We consider a system at vanishing temperature with nonzero isospin chemical potential and strangeness chemical potential; meson masses and mixing in the normal phase, the pion condensation phase and the kaon condensation phase are described. We find differences with previous works, but the results presented here are supported by both theory group analysis and by direct calculations. Some pion decay channels in the normal and the pion condensation phases are studied, finding a nonmonotonic behavior of the decay width as a function of μ I. Furthermore, pressure, density and equation of state of the system at T = 0 are studied, finding remarkable agreement with analogue studies performed by lattice calculations.
Cold three flavor quark matter at large (but not asymptotically large) densities may exist in a c... more Cold three flavor quark matter at large (but not asymptotically large) densities may exist in a crystalline color superconducting phase. These phases are characterized by a gap parameter $\Delta$ that varies periodically in space, forming a crystal structure. A Ginzburg-Landau expansion in $\Delta$ shows that two crystal structures based on cubic symmetry are particularly favorable, and may be the ground state of matter at densities present in neutron star cores. We derive the effective action for the phonon fields that describe space- and time-dependent fluctuations of the crystal structure formed by $\Delta$, and obtain the shear modulus from the coefficients of the spatial derivative terms. Within a Ginzburg-Landau approximation, we find shear moduli which are 20 to 1000 times larger than those of neutron star crusts. This phase of matter is thus more rigid than any known material in the universe, but at the same time the crystalline color superconducting phase is also superfluid...
We analyze the effect of restricted geometries on the contribution of Nambu-Goldstone bosons (pho... more We analyze the effect of restricted geometries on the contribution of Nambu-Goldstone bosons (phonons) to the shear viscosity, $\eta$, of a superfluid. For illustrative purpose we examine a simplified system consisting of a circular boundary of radius $R$, confining a two-dimensional rarefied gas of phonons. Considering the Maxwell-type conditions, we show that phonons that are not in equilibrium with the boundary and that are not specularly reflected exert a shear stress on the boundary. In this case it is possible to define an effective (ballistic) shear viscosity coefficient $\eta \propto \rho_{\rm ph} \chi R$, where $\rho_{\rm ph}$ is the density of phonons and $\chi$ is a parameter which characterizes the type of scattering at the boundary. For an optically trapped superfluid our results corroborate the findings of Refs. \cite{Mannarelli:2012su, Mannarelli:2012eg}, which imply that at very low temperature the shear viscosity correlates with the size of the optical trap and decr...
The oscillation of neutrons n into mirror neutrons n', their mass degenerate partners from da... more The oscillation of neutrons n into mirror neutrons n', their mass degenerate partners from dark mirror sector, can have interesting implications for neutron stars: an ordinary neutron star could gradually transform into a mixed star consisting in part of mirror dark matter. Mixed stars can be detectable as twin partners of ordinary neutron stars: namely, there can exist compact stars with the same masses but having different radii. For a given equation of state (identical between the ordinary and mirror components), the mass and radius of a mixed star depend on the proportion between the ordinary and mirror components in its interior which in turn depends on its age. If 50 % - 50% proportion between two fractions can be reached asymptotically in time, then the maximum mass of such "maximally mixed stars" should be √(2) times smaller than that of ordinary neutron star while the stars exceeding a critical mass value M^ max_NS/√(2) should collapse in black holes after cer...
arXiv: High Energy Physics - Phenomenology, 2009
Some results about dissipative processes in superfluids are presented. We focus on fermionic supe... more Some results about dissipative processes in superfluids are presented. We focus on fermionic superfluidity and restrict our analysis to the contribution of phonons to bulk viscosity, shear viscosity and thermal conductivity. At sufficiently low temperatures phonons give the dominant contribution to the transport coefficients if all the other low energy excitation of the system are gapped. We first consider a system of cold fermionic atoms close to the unitarity limit. Then we turn to the superfluid phase of quark matter that may be realized at high baryonic density.
This thesis represents the results of work have done during my PhD studies at L’Aquila University... more This thesis represents the results of work have done during my PhD studies at L’Aquila University and Gran Sasso National Laboratory (LNGS). We investigated the role played by quark crust in providing new observable signatures that can attest to the presence of color superconductivity in the interior of compact stars; new results are found. The idea that strange quark matter (SQM) may be the ground state of strongly interacting dense matter, rather than normal atomic nuclei (Fe), was proposed already in the early 1970s. If correct, the SQM hypothesis would have implications of fundamental importance for our understanding of the early universe and the evolution of compact stars. The purpose of this thesis is to investigate the possibility that SQM is present in compact stars, studying the possible observational consequences. As the observations of oscillations of ordinary stars can be used to determine their composition and structure, the oscillations of quark stars could potentially...
The European Physical Journal C
The oscillation of neutron n into mirror neutron $$n'$$ n ′ , its mass degenerate partner fro... more The oscillation of neutron n into mirror neutron $$n'$$ n ′ , its mass degenerate partner from dark mirror sector, can gradually transform the neutron stars into the mixed stars consisting in part of mirror dark matter. In quark stars $$n-n'$$ n - n ′ transitions are suppressed. We study the structure of mixed stars and derive the mass-radius scaling relations between the configurations of purely neutron star and maximally mixed star (MMS) containing equal amounts of ordinary and mirror components. In particular, we show that the MMS masses can be at most $$M^{\mathrm{max}}_{NS}/\sqrt{2}$$ M NS max / 2 , where $$M^\mathrm{max}_{NS}$$ M NS max is a maximum mass of a pure neutron star allowed by a given equation of state. We evaluate $$n-n'$$ n - n ′ transition rate in neutron stars, and show that various astrophysical limits on pulsar properties exclude the transition times in a wide range $$10^{5}\,\text {year}< \tau _\varepsilon < 10^{15}\,\text {year}$$ 10 5 year...
Physical Review D
Acoustic holes are the hydrodynamic analogue of standard black holes. Featuring an acoustic horiz... more Acoustic holes are the hydrodynamic analogue of standard black holes. Featuring an acoustic horizon, these systems spontaneously emit phonons at the Hawking temperature. We derive the Hawking temperature of the acoustic horizon by fully exploiting the analogy between black and acoustic holes within a covariant kinetic theory approach. After deriving the phonon distribution function from the covariant kinetic equations, we reproduce the expression of the Hawking temperature by equating the entropy and energy losses of the acoustic horizon and the entropy and energy gains of the spontaneously emitted phonons. Differently from previous calculations we do not need a microscopical treatment of normal modes propagation. Our approach opens a different perspective on the meaning of Hawking temperature and its connection with entropy, which may allow an easier study of non stationary horizons beyond thermodynamic equilibrium, including dissipative effects.
Proceedings of VIIIth Conference Quark Confinement and the Hadron Spectrum — PoS(ConfinementVIII)
Cold three flavor quark matter at large (but not asymptotically large) densities may exist in a c... more Cold three flavor quark matter at large (but not asymptotically large) densities may exist in a crystalline color superconducting phase. These phases are characterized by a gap parameter ∆ that varies periodically in space, forming a crystal structure. A Ginzburg-Landau expansion in ∆ shows that two crystal structures based on cubic symetry are particularly favorable, and may be the ground state of matter at densities present in neutron star cores. We derive the effective action for the phonon fields that describe space-and time-dependent fluctuations of the crystal structure formed by ∆, and obtain the shear modulus from the coefficients of the spatial derivative terms. Within a Ginzburg-Landau approximation, we find shear moduli which are 20 to 1000 times larger than those of neutron star crusts. This phase of matter is thus more rigid than any known material in the universe, but at the same time the crystalline color superconducting phase is also superfluid. These properties raise the possibility that the presence of this phase within neutron stars may have distinct implications for their phenomenology. For example, (some) pulsar glitches may originate in crystalline superconducting neutron star cores.
Proceedings of VIIIth Conference Quark Confinement and the Hadron Spectrum — PoS(ConfinementVIII)
Particles
We give a pedagogical review of the properties of the various meson condensation phases triggered... more We give a pedagogical review of the properties of the various meson condensation phases triggered by a large isospin or strangeness imbalance. We argue that these phases are extremely interesting and powerful playground for exploring the properties of hadronic matter. The reason is that they are realized in a regime in which various theoretical methods overlap with increasingly precise numerical lattice QCD simulations, providing insight on the properties of color confinement and of chiral symmetry breaking.
The European Physical Journal C
We revisit two-color, two-flavor chiral perturbation theory at finite isospin and baryon density.... more We revisit two-color, two-flavor chiral perturbation theory at finite isospin and baryon density. We investigate the phase diagram obtained varying the isospin and the baryon chemical potentials, focusing on the phase transition occurring when the two chemical potentials are equal and exceed the pion mass (which is degenerate with the diquark mass). In this case, there is a change in the order parameter of the theory that does not lend itself to the standard picture of first order transitions. We explore this phase transition both within a Ginzburg-Landau framework valid in a limited parameter space and then by inspecting the full chiral Lagrangian in all the accessible parameter space. Across the phase transition between the two broken phases the order parameter becomes an SU (2) doublet, with the ground state fixing the expectation value of the sum of the magnitude squared of the pion and the diquark fields. Furthermore, we find that the Lagrangian at equal chemical potentials is invariant under global SU (2) transformations and construct the effective Lagrangian of the three Goldstone degrees of freedom by integrating out the radial fluctuations.
EPJ Web of Conferences
We discuss an innovative method for the description of inhomogeneous phases designed to improve t... more We discuss an innovative method for the description of inhomogeneous phases designed to improve the standard Ginzburg-Landau expansion. The method is characterized by two key ingredients. The first one is a moving average of the order parameter designed to account for the long-wavelength modulations of the condensate. The second one is a sum of the high frequency modes, to improve the description of the phase transition to the restored phase. The method is applied to compare the free energies of 1D and 2D inhomogeneous structures arising in the chirally symmetric broken phase.
Uploads
Papers by Massimo Mannarelli