N-body Simulations: Density vs Circular Profiles

[Ranku]

N-body simulations of rotating galaxies involve density profile and circular profile. Would it be accurate to say that the essential difference between density profile and circular profile is that the former involves gravitational mass while the latter involves inertial mass?

 

[jedishrfu]

I don’t think that’s the case since the equivalence principle holds that gravitational mass is equivalent to inertial mass.

https://en.m.wikipedia.org/wiki/Equivalence_principle

Do you have code examples that illustrate this? It could well be that different programmers used different names for the same thing.

 

[Ranku]

I don’t think that’s the case since the equivalence principle holds that gravitational mass is equivalent to inertial mass.

https://en.m.wikipedia.org/wiki/Equivalence_principle

Do you have code examples that illustrate this? It could well be that different programmers used different names for the same thing.

My question was triggered by a paper by Navarro, Frenk, and White, where they do density profile and circular velocity profile of rotation curve in disk galaxies. It is seen that the density profile seems to adhere more closely than circular velocity profile to rotation curve.

It is true that the principle of equivalence makes no distinction between gravitational mass and inertial mass, in linear and rotational freefall of an object. Galaxies, however, involve a distribution of masses, which are themselves in graviational interaction, and therefore the situation is more complicated. How complicated is something to be be analyzed and debated. What I am trying to clarify, however, is can we make a distinction between density profile and circular velocity profile in terms of gravitational mass and inertial mass. Circular velocity profile involves the orbital velocity formula, which is derived by equating gravitational force and centrifugal force, and therefore involves inertial mass. Density profile, as the name indicates, deals with the density of matter. Now does that therefore imply that essentially only the dynamics of gravitational mass is being considered in density profile?
If you are technically familiar with N-body simulations, perhaps you could clarify this matter.

 

[Chronos]

Despite the broad profiles offered by distant galaxies, the precise nature of galactic evolution remains a hotly debated topic.