Inhomogeneous seeding of quark bubbles in neutron stars M Ángeles Pérez-García Department of Fundamental Physics University of Salamanca, Spain 1

Neutron stars are among the most dense stars. Current experimental mass and radii determination can be accommodated assuming composition. Either nucleon/quark content are theoretically allowed in existing models. Some EOS provide too low massive objects, resulting disfavoured. Some crustal properties indicate nucleon nature Standard picture of a NS 2 Page et al, ApJ 155 (2004)

Back in the 70’s: (strange) quark matter Two seminal papers pointed out the possibility of other possible composition for compact stars and lower energetic states

Raising degeneracy in NS Fraga et al, ApJL ) The effect of modelization of quarks in a deconfined phase is still under study. But the most important point is How can the deconfinement be triggered? A number of different sources of activation have been proposed: SN Collapse: Benvenuto, Horvath, Vucetich IJMPA 4, (1989) Sagert et al, PRL 102 (2009) Delayed times: Bombaci et al, ApJ 614(2004). Drago et al, PRD 69 (2004) Staff,Ouyed,Jaikumar, ApJ 645 (2006)

Theory of hot-spikes is developed by Seitz, Phys. Fluids, 1, 2 (1958). An inhomogenous nucleation of seeds needs from an energy spike Vineyard, Radiation Effects, 29(1976) Quenching of the excited state if a hot-spike is generated is observed Typical fluctuation needed in a medium is Hot spikes: Seitz theory 5

Laser and spark induced bubbles Sato et al, Appl. Phys. Lett. 102 (2013)

7 Activation can be achieved by an external agent: dark matter Dark matter is another component in our universe, >80% of matter content. SDSS finds This is not baryonic matter, DM does not mix with photon fluid. Thermal CS Evidence from: CMB measurements, gravitational lensing, gravitational interaction.. Dark matter candidates exist in large variety: WIMPs, Axions, MACHOS,.. Nucleation by external agents: dark matter

T. Linden, U. Chicago

Dark matter trapped inside NSs 9 arXiv: Weakly interacting dark matter may be efficiently captured by progenitors and NSs. Gravitationally thermalized if CS Typical mean free paths allow several scatterings on radial scale before capture

Building up an internal DM distribution 10 We consider a model where DM self-annihilates NS Capture rate [Gould 1987] yields a solution with a DM population partially inherited from the progenitor. Perez-Garcia, Silk arXiv:

DM distribution inside the (Proto)NS 11 The number of DM particles inside is related to the gravitationally accreted distribution In this way a thermal radius (<R PNS ) Baryonic and dark matter are overlapping distributions. Energy and heat is transferred right in the center of the PNS.

Energy deposit from DM annihilation 12 The energy deposit rate from decays with and a hard photon/neutrino spectrum for different channels If instead of annihilating DM has a decaying nature Over time the average energy density in a NS lifetime The local energy deposit must allow nucleation

13 Work to create a quantum bubble has been estimated (Landau 1980, Alcock and Olinto 1989) For liquid-vapor phases in the superheated classical liquids The energy density to create such a bubble (m q =0) is [Madsen 2007] It has been estimated that a few MeV Temperature fluctuation can cause a quark deconfinement transition able to nucleate stable bubbles in a cold system i.e. Energy needed for bubble formation

Trigger allowed for light DM Dark matter driven spark seeding may provide the triger Affecting additionally: 1) Rotational patterns 2) Cooling properties Negreiros, Dexheimer, Schramm, PRC 85, (2012) Perez-Garcia, Silk, Stone PRL 105, (2010) Perez-Garcia, Silk, PLB 711, 6 (2012)

DM scattering vs annihilation inside the NS Large numbers of annihilations happen at the central pit in the NS. Panci, Perez-Garcia, Silk submitted

Thermal cross section and bubble formation Annihilation over NS lifetime can be tested if the energy released is a function of time Low thermal cross sections would delay destabilization until late times. If the number of bubbles is related to a threshold in the perturbation in hydrostatic values would yield transition at late times. Typically the injection of energy is and narrow spreading

17 Current searches with bubble chambers try to detect bubbles generated in superheated liquid from nuclear recoils Much experience e.g. PICASSO, COUPP, SIMPLE Considering a “classical liquid” a bubble survives to be detected if -superheated liquid state -radius is larger than critical radius r>Rc -energy to nucleate the bubble is large enough Chemical sparks may induce nucleation of bubbles as well. More bubbles

18 The number of internal decays is recovered in the linear limit since we expect Typical time scales > yr In this way The number of particle decays inside the NS assuming interpretations of e+e- data in terms of decaying DM in the context of GUT Decay channels Similar to Proton decay searches [Ibarra et al, JCAP01 (2010),M. Garny et al, JCAP025 (2012)]

If DM is heavy enough and decays this behavior is capable of producing additional indirect effects Bubble formation can trigger changes in the Equation of State (EoS) by altering the pressure-energy density relation Number of stable bubbles created is Quark nova model predicts large GRB Harko et al. ApJ 608 (2004) 945 demostrate one single bubble may trigger macroscopic conversion NS  QS emittig sGRB. Conservatively one may assume a “mechanical instability” in the GC ensamble Bubble instability Ouyed, Dey A&A (2002)

In this scenario finite quark matter lumps (i.e. nuclearites, strangelets) could be primaries Kinetic energies due to gravitational energy conversion E injected into the expelled outer crust for standard NS mass and radius A − lumps could then gain energies of order the typical energy observed in hotspot Fragmentation and ejection of SQM Perez-Garcia, Daigne, Silk, ApJ 768 (2013) 20 Kotera, Pérez-García, Silk PLB 2013 Benvenuto, Horvath 1989 Madsen 2006, Horvath, Paulucci 2007

Conclusions 21 DM annihilation may provide an efficient way to trigger nucleation in the central core of NSs Inhomogeneous mechanism should happen macroscopically to perturbate the hydro equilibrium Dynamical behaviour still to be determined since evolution of bubbles is key to the mechanism. Bulk not enough.