How do scientists make sophisticated calculations in general relativity?

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Discussion Overview

The discussion centers on how scientists perform sophisticated calculations in general relativity, particularly regarding the use of algorithms and computational tools to solve complex equations. Participants explore the challenges of solving nonlinear equations and the role of computer assistance in these calculations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions the methods used by scientists for complex calculations in general relativity and inquires about special algorithms.
  • Another participant notes that many equations in physics, including those in general relativity, are nonintegrable analytically and often require computer assistance for solutions.
  • Some participants mention that while certain solutions, like the Schwarzschild solution, can be derived analytically, most calculations necessitate computational tools.
  • There is a suggestion that symbolic tensorial and spinorial calculations may be done by hand, but for more complex systems, specialized software or algorithms are necessary.
  • Participants discuss various tools, such as GRTensor, for symbolic verification and evaluation of tensor components, and recommend resources for further exploration of numerical relativity.
  • One participant emphasizes the need for strong software or a small supercomputer to effectively solve the equations beyond symbolic calculations.

Areas of Agreement / Disagreement

Participants generally agree on the necessity of computational tools for solving complex equations in general relativity, but there is no consensus on the specific methods or algorithms that should be used.

Contextual Notes

The discussion highlights the limitations of current methods, including the dependence on computational resources and the challenges posed by nonlinear partial differential equations. There is also an acknowledgment of the potential for symbolic calculations but with an emphasis on the need for more robust solutions.

Starship
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How do professional scientists make sophisticated calculations, e.g the http://arxiv.org/PS_cache/math-ph/pdf/0412/0412064.pdf in general relativity? Are there any special algorithms for this?

I'd really like to solve these equations but it's almost impossible without computer help.
 
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Using calculators...?The equations in physics are usually nonintegrable analytically,many of them are quasi/nonlinear (starting with Newton's gravity law,for example) and therefore the dynamics is found either intuitively or using a computer...

There are fortunate exceptions...The Schwarzschild solution is one of them.

Daniel.
 
dextercioby said:
Using calculators...?The equations in physics are usually nonintegrable analytically,many of them are quasi/nonlinear (starting with Newton's gravity law,for example) and therefore the dynamics is found either intuitively or using a computer...

There are fortunate exceptions...The Schwarzschild solution is one of them.

Daniel.

Thanks dexter. Do i need to develop my own algorithms?

The Einstein equations are nonlinear, therefore are very difficult to solve without a computer.
 
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Starship said:
How do professional scientists make sophisticated calculations, e.g the http://arxiv.org/PS_cache/math-ph/pdf/0412/0412064.pdf in general relativity? Are there any special algorithms for this?

I'd really like to solve these equations but it's almost impossible without computer help.

The symbolic tensorial and spinorial calculations in the paper above are probably done by hand.
One can use tools like GRTensor and others to symbolically verify some calculations or evaluate tensor components [given component functions of the metric, for example].

To go beyond symbolic calculations, you'll need to find or write specialized software to solve systems of nonlinear PDEs. For these, you might start here
http://jean-luc.aei.mpg.de/
http://numrel.aei.mpg.de/
http://bh0.physics.ubc.ca/People/matt/555/
and the Numerical Relativity articles at
http://relativity.livingreviews.org/Articles/subject.html
 
Last edited by a moderator:
robphy said:
The symbolic tensorial and spinorial calculations in the paper above are probably done by hand.
One can use tools like GRTensor and others to symbolically verify some calculations or evaluate tensor components [given component functions of the metric, for example].

To go beyond symbolic calculations, you'll need to find or write specialized software to solve systems of nonlinear PDEs. For these, you might start here
http://jean-luc.aei.mpg.de/
http://numrel.aei.mpg.de/
http://bh0.physics.ubc.ca/People/matt/555/
and the Numerical Relativity articles at
http://relativity.livingreviews.org/Articles/subject.html

Thanks robphy. This was a great help.

Most of these calculations are indeed symbolic but in order to really solve it, one either needs a strong software or a small supercomputer with a quite simple algorithm.
 
Last edited by a moderator:

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