The Reissner-Nordstrom metric

  • Context: Graduate 
  • Thread starter Thread starter Orion1
  • Start date Start date
  • Tags Tags
    Metric
Click For Summary

Discussion Overview

The discussion centers around the Reissner-Nordstrom metric in the context of General Relativity, specifically regarding its application to spinless charged neutron stars. Participants explore the implications of different equations for electric charge and their relation to metric components, as well as the contribution of charge to the mass of these stars.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants reference two different equations for electric system charge, questioning how they relate to the metric components \nu and \lambda.
  • There is a query regarding why one equation includes two metric components while the other only includes one.
  • Concerns are raised about the dimensional consistency of the equations, particularly the absence of r^2 dimensions in one of the equations.
  • Participants seek clarification on the International System of Units (S.I.) for the quantities j^0 and \rho_{ch}.
  • Another participant presents an equation for the total mass of a charged neutron star and asks how charge contributes to mass in this formulation.
  • One participant derives a formula for the relativistic electric field and discusses the implications of the metric components on this formula.
  • There is a suggestion that the relationship between j^0 and \rho_{ch} could be expressed as j^0 = \rho_{ch} r^2.

Areas of Agreement / Disagreement

Participants express multiple competing views on the equations and their implications, indicating that the discussion remains unresolved with no consensus reached on the interpretations or relationships between the various components and equations.

Contextual Notes

Participants note limitations in understanding the dimensional analysis of the equations and the assumptions underlying the definitions of the quantities involved.

Orion1
Messages
961
Reaction score
3

Two citations referenced by Wikipedia with respect to General Relativity models for spinless charged neutron stars, reference 2 - eq. 24, states that the Reissner-Nordstrom metric relativistic Einstein-Maxwell Gauss law for the electric system charge is:
[tex]Q(r) = \int_0^r 4 \pi j^0 e^{\frac{(\nu + \lambda)}{2}} dr[/tex]

However, according to reference 3 - eq. 5, the electric system charge is:
[tex]Q(r) = \frac{1}{r^2} \int_0^r 4 \pi r^2 \rho_{ch} e^{\frac{\lambda}{2}} dr[/tex]

What Einstein-Maxwell charge effects with respect to the metric components [tex]\nu[/tex] and [tex]\lambda[/tex] are these equations describing?

Why does the reference 2 equation have two metric components and the reference 3 equation has only one metric component?

Why is the reference 2 equation missing the [tex]r^2[/tex] dimensions?

And what are the International System of Units (S.I.) for [tex]j^0[/tex] and [tex]\rho_{ch}[/tex]?

Please post links to this thread for subject equations cross-reference.
[/Color]
Reference:
http://en.wikipedia.org/wiki/Reissner%E2%80%93Nordstr%C3%B6m_metric"
http://arxiv.org/PS_cache/arxiv/pdf/0705/0705.2708v2.pdf"
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-97332004000200038"
 
Last edited by a moderator:
Astronomy news on Phys.org
total mass of charged neutron star...


How was this equation generated?

Total mass of spinless charged neutron star at a radial distance r:
[tex]\frac{dm(r)}{dr} = \frac{4 \pi r^2 \epsilon(r)}{c^2} + \frac{Q(r)}{c^2 r} \frac{dQ(r)}{dr}[/tex]

How exactly does charge contribute to mass this way?
[/Color]
Reference:
http://arxiv.org/PS_cache/arxiv/pdf/0705/0705.2708v2.pdf"
 
Last edited by a moderator:

Please post links to this thread for subject equations cross-reference.
[/Color]
 
Last edited:
nu metric component...



Given that [tex]F^{\mu \kappa}[/tex] satifies the covariant Maxwell field equation:
[tex]\left[\sqrt{-g} F^{\kappa \mu} \right]_{, \mu} = 4 \pi J^{\kappa} \sqrt{-g}[/tex]

The quantity [tex]J^{\kappa}[/tex] denotes the four-current which represents the electromagnetic sources in the star. For a static spherically symmetric system, the only non-zero component of the four-current is [tex]J^1[/tex], which implies that the only non-vanishing component of [tex]F^{\kappa \mu}[/tex] is [tex]F^{01}[/tex]:

In this case I derived this formula for the relativistic electric field:
[tex]F^{01}(r) = E(r) = \frac{Q(r)}{r^2} e^{- \frac{ \left( \nu + \lambda \right)}{2}}[/tex]

The formula suggested by the remaining reference papers:
[tex]F^{01}(r) = E(r) = \frac{Q(r)}{r^2}[/tex]

Electric system charge:
[tex]Q(r) = \int_0^r 4 \pi j^0 e^{\frac{ \left( \nu + \lambda \right)}{2}} dr[/tex]

The formula suggested by the remaining reference papers:
[tex]Q(r) = \int_0^r 4 \pi r^2 \rho_{ch} e^{\frac{\lambda}{2}} dr[/tex]

Therefore:
[tex]\boxed{j^0 = \rho_{ch} r^2}[/tex]

Integration by substitution:
[tex]F^{01}(r) = E(r) = \frac{e^{- \frac{ \left( \nu + \lambda \right)}{2}}}{r^2} \int_0^r 4 \pi j^0 e^{\frac{ \left( \nu + \lambda \right)}{2}} dr[/tex]

Why does this solution have a [tex]\nu[/tex] metric component and two metric components relativistic electric_field modifier [tex]e^{- \frac{ \left( \nu + \lambda \right)}{2}}[/tex]?
[/Color]
Reference:
http://en.wikipedia.org/wiki/Reissner%E2%80%93Nordstr%C3%B6m_metric"
http://arxiv.org/PS_cache/arxiv/pdf/0705/0705.2708v2.pdf"
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-97332004000200038"
http://www.google.com/url?sa=t&sour...o.pdf&usg=AFQjCNG7gtMPDuwpTrqYwoZ2NuS1lk1nRw"
 
Last edited by a moderator:

Similar threads

  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 19 ·
Replies
19
Views
4K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 22 ·
Replies
22
Views
7K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 5 ·
Replies
5
Views
4K