• PDF / 280,054 Bytes
• 8 Pages / 612 x 792 pts (letter) Page_size
• 85 Downloads / 203 Views

DOWNLOAD

REPORT

---

eutrino Radiation from Dense Matter¶ A. Sedrakian Institute for Theoretical Physics, Tübingen University, D-72076 Tübingen, Germany Abstract—This article provides a concise review of the problem of neutrino radiation from dense matter. The subjects addressed include quantum kinetic equations for neutrino transport, collision integrals describing neutrino radiation through charged and neutral current interactions, and radiation rates from pair-correlated baryonic and color superconducting quark matter. PACS numbers: 13.15.+g DOI: 10.1134/S1063779608070319

1. INTRODUCTION After an initial phase of rapid (of the order of weeks to years) cooling from temperatures T ~ 50 MeV down to 0.1 MeV, a neutron star’s core settles in a thermal quasi-equilibrium state which evolves slowly over the time scales 103–104 yr down to temperatures T ~ 0.01 MeV. The cooling rate of the star during this period is determined by the processes of neutrino emission from dense matter, whereby the neutrinos, once produced, leave the star without further interactions. Understanding the cooling processes that take place during this neutrino radiation era is crucial for the interpretation of the data on surface temperatures of neutron stars. While the long-term features of the thermal evolution of neutron stars are insensitive to the initial rapid cooling stage, the subsequent route in the temperature versus time diagram, which includes the late time (t ≥ 105 yr) photoemission era, strongly depends on the emissivity of matter during the neutrino cooling era. This lecture is a concise introduction to the physics of neutrino radiation from dense nucleonic and quark matter in compact stars. It starts with a classification of the reactions in Section 1.1, which is followed by a discussion of quantum kinetic equations for neutrinos and neutrino emissivities in Section 2. In Section 3 examples are given of polarization tensors of superfluid nucleonic matter and color superconducting quark matter. We close by suggesting two exercises for students. 1.1. Classification of the Reactions

text was submitted by the author in English.

f 2 + e + ν,

f1 f

f2 + e

f +ν+ν

f 1 + ν,

( forbidden ),

(1) (2)

where the first line is the charged current β-decay and its inverse, with f1 and f2 being neutron and proton quasiparticles in nucleonic matter or d and u flavor quarks in deconfined quark matter; f refers to a fermion. This process is known in astrophysics as the Urca processes [1]. The Urca reaction is kinematically allowed in nucleonic matter under β-equilibrium if the proton fraction is sufficiently large, Yp ≥ 11–14% [2]. In deconfined, chirally symmetric, and interacting quark matter at moderate densities, the Urca processes is kinematically allowed for any asymmetry between u and d quarks [3]. The second process, the neutral current neutrino pair bremsstrahlung, Eq. (2), is forbidden by the energy and momentum conservation, if one adopts the quasiparticle picture. If, however, we choose to work with excitations that are characterized by finite widths, re