Electron-positron pair productions in gravitational - PowerPoint Presentation

Slide1

Electron-positron pair productions in gravitational collapses

In collaboration with Wen-Biao Han, & Remo Ruffini ICRANet & Physics Department, University of Rome

She-Sheng Xue

MG13, Stockholm, July 5

th

, 2012Slide2

Motivation

We attempt to study the possibility of electron-positron pair productions in variations of electrical field and energy in pulsation and collapsing of neutral compact star cores.We show a possible way that gravitational energy can be converted to electromagnetic energy in stellar core collapse and pulsation, possibly accounting for high-energy Gamma-Ray emissions. Slide3

t

Pair plasma oscillations

Already discussed

Pairs

and

photon

plasma

Hydrodynamic

expansion

Already

discussed

Already

discussed

R.

Ruffini

, J.D.

Salmonson

,

J.R.Wilson

,

S.-S.

Xue

A&A 350 (1999) 334; 359, (2000) 855 .

R.

Ruffini

, L.

Vitagliano

, S.-S.

Xue

,

PLB 573 (2003) 33; 559 (2003) 12.

Electron-positron pairs production and evolution in gravitational

collapses of charged cores and strong fields

R

Initial conditions of strong charged cores and

Fields are hardly justified !!!Slide4

Strong (overcritical) electric fields in surface layer of stellar cores

Quark stars (e.g. Usov, PRL 80, 230, 1997;…..); Neutron stars (e.g. M. Rotondo, Jorge A. Rueda, R. Ruffini and S.-S. Xue, Phys. Rev. C83, D84 (2011); Phys. Lett. B701 (2011), Nucl.Phys. A872 (2011).....) Modeling strong and weak interactions, we solve the Einstein-Maxwell-Thomas-Fermi equations, Blue: protonRed: electron

Overcritical field

Electron-positron pair productions are not

permitted by Pauli blocking.

+

_Slide5

Macroscopic and microscopic processes

(i) macroscopic processes: gravitational pulsation, and collapse, hydrodynamic… (slowly varying in large length scale) , described by equations of fields and rates.(ii) microscopic processes: strong and electroweak interactions, thermal collisions … (fast varying in short length scale), described by equations of fields and rates. Local and instantaneous approximationEquations of states (distribution functions) and particle number conservations.

This approximation is adopted in both analytical and numerical approaches. Indeed, it is a good approximation for fields and their variations are small.

On the other hand, it is difficult to solve these sets of equations of fields and

particles interacting at very different scales: meter and Compton length.

Slide6

Two space-time scales of the problem

There are two space-time scales in core collapses: One is the gravitational interaction scale: in meter and second ;Another is the electromagnetic interaction scale:in Compton length and Compton time.This means it is almost impossible to numerically simulate the two processes together! We treat them independently: the core collapse given by analytical collapse equation and the electron-fluid dynamics calculated numerically in Compton space-time scale.Slide7

Electromagnetic field and processes

In local and instantaneous approximation, electric field and processes are eliminated in a neutral system, due to electric charge conservation.Internal electric fields can be developed by a dynamics acting differently on positive and negative charges (see for example E. Olson and M. Bailyn, Phys. Rev. D 12, 3030 (1975), and D 13, 2204 (1976), and M. Rotondo, Jorge A. Rueda, R. Ruffini and S.-S. Xue, Phys. Rev. C 83, 045805 (2011); Phys. Lett. B 701, 667 (2011)). If electric fields are weak and slowly vary in space and time, the validity of local and instantaneous approximation can be justified.

However, electric fields are so strong (overcritical) and fast vary in space and time,

that very rapid electric processes, like electron- positron pair productions, can take

place. In this case, we are forced to give up the local and instantaneous approximation,

and integrate Maxwell equation of fields and rate-equations of particles, as well as

equations for energy-momentum conservations. We study this possibility.Slide8

Dynamical equationsSlide9

Baryon core and its gravitational collapse (pulsation)

to be determined by Einstein equation for gravitational collapse.Core collapsing velocitySlide10
Slide11

Initial and Equilibrium configurations

Blue: protonRed: electron

+_Slide12

Electric field and Electrons: Maxwell equation, continuous, energy-momentum conservations and equation of stateSlide13

Oscillations and RelaxationSlide14

Oscillation, relaxation and energy-conservation

The relaxation from one equilibrium configuration to another

Oscillating energySlide15

Electron-positron pair productions in oscillating electric fields

Occupied electron levelsH. Kleinert, R. Ruffini, S.-S. Xue, PRD 78 (2008) 025001.Slide16

Pair-production rateSlide17

Core gravitational collapse

C. Cherubini, R. Ruffini and L. Vitagliano, Phys.~Lett.~B545 (2002) 226.Slide18

Dyadosphere of electron and positron pairs

The energy-number densities and total energy-number of electron-positron pairs are the same order as that estimated in the model of dyadosphere.Slide19

Some remarks.Cores undergo either collapses or pulsations, depending on the balance between attractive gravitational energy and repulsive electric and internal energies. The pulsation frequency can be expressed as

The adiabatic approximation we adopted is self-consistently and quantitatively justified by process rates pair plasma oscillation and pair-photon plasma rates. Nevertheless, these results should be further verified by numerical algorithms integrating Einstein-Maxwell equations in gravitational collapses.The possible consequences of these electromagnetic processes discussed could be relevant and important for explaining energetic sources of Soft-Gamma-Ray Repeaters (SGRs) and progenitors of Gamma-Ray Bursts (GRBs).Slide20

The existence of a

separatrix is a general relativistic effect: the radius of the gravitational trap is

The fraction of energy available in the expanding plasma is

about 1/2.