by bellanto » Tue Nov 22, 2005 4:36 pm
APOD for 22 Nov 2005 shows a pair of interacting galaxies in some colliding galactic groups. There is a long thin string of stars between the two galaxies, over on the left hand side of the picture. Such structures are also thought to occur on a scale of 10^-15 meters, when hadrons (such as protons and neutrons) collide. Now the force between the parts of the hadrons have the property that the the force itself is subject to the force; this is not like gravity as we normally think of it. A planet might feel the effect of the sun's gravity, but what ever it is that goes from the sun to the planet is not itself subject to gravity, I think. Or an electric field might pull on a charged particle but is not itself charged. But the forces between quarks do have this property and the result is that the particles carrying the force are attracted to each other. So this nuclear force does not spread out in the usual way... the field lines are contained in strings. The energy density in the string is roughly constant, so the force between the particles is roughly constant rather than obeying a 1 over r-sqared law like gravity or in Coulomb's law.
My question is, if one allows for the energy density of the stars in the structure, is a constant-force, fixed energy density approximation a reasonable one for intergalactic attraction in collisions? The density of stars in the stringy structure in the left of today's photo looks roughly uniform and hence the energy density - that is the source term for the gravitational field - might be pretty uniform.
APOD for 22 Nov 2005 shows a pair of interacting galaxies in some colliding galactic groups. There is a long thin string of stars between the two galaxies, over on the left hand side of the picture. Such structures are also thought to occur on a scale of 10^-15 meters, when hadrons (such as protons and neutrons) collide. Now the force between the parts of the hadrons have the property that the the force itself is subject to the force; this is not like gravity as we normally think of it. A planet might feel the effect of the sun's gravity, but what ever it is that goes from the sun to the planet is not itself subject to gravity, I think. Or an electric field might pull on a charged particle but is not itself charged. But the forces between quarks do have this property and the result is that the particles carrying the force are attracted to each other. So this nuclear force does not spread out in the usual way... the field lines are contained in strings. The energy density in the string is roughly constant, so the force between the particles is roughly constant rather than obeying a 1 over r-sqared law like gravity or in Coulomb's law.
My question is, if one allows for the energy density of the stars in the structure, is a constant-force, fixed energy density approximation a reasonable one for intergalactic attraction in collisions? The density of stars in the stringy structure in the left of today's photo looks roughly uniform and hence the energy density - that is the source term for the gravitational field - might be pretty uniform.