by alter-ego » Sun Sep 11, 2011 5:19 am
ErnieM wrote:
How is dark matter converted into dark energy?
DM and DE are not necessarily correlated, at least in the sense the one is, or can be, converted to another. Keep in mind that DM and DE are apparent entities that are not understood, but manifest themselves in comological observations and supported by GR (Lambda-CDM) model. Also, the concept of an expanding Universe was a direct consequence of GR, whence the origin of Lambda (
Λ) the cosmological constant. It is interesting that DE and GR have an apparently intrinsic connection, but DM is not born from GR. Thus it seems reasonable, today, that DM and DE are viewed as distinct, uncorrelated, entities despite not knowing what they really are.
Does dark matter follows Einstein's E = mc2?
I think it's fair to say that since DM can be effectively mapped / modeled by gravitational lensing and stellar velocity distributions (e.g. within a galaxy), and the observed gravitational effects on its surroundings are not distinguishable from that due to baryonic (normal) matter, the idea of DM and energy equivalence is valid. However, applying Einstein's energy equivalence to DE does not make sense. DE / Vacuum Energy imply a repulsuve gravitational field.
[quote="
Wiki"]The vacuum energy also has important consequences for physical cosmology. Special relativity predicts that energy is equivalent to mass, and therefore, if the vacuum energy is "really there", it should exert a gravitational force. Essentially, a non-zero vacuum energy is expected to contribute to the cosmological constant, which affects the
expansion of the universe. In the special case of vacuum energy, general relativity stipulates that the gravitational field is proportional to ρ-3p (where ρ is the mass-energy density, and p is the pressure). Quantum theory of the vacuum further stipulates that the pressure of the zero-state vacuum energy is always negative and equal to ρ. Thus, the total of ρ-3p becomes -2ρ: A negative value.
This calculation implies a repulsive gravitational field, giving rise to expansion, if indeed the vacuum ground state has non-zero energy. However, the vacuum energy is mathematically infinite without renormalization, which is based on the assumption that we can only measure energy in a relative sense, which is not true if we can observe it indirectly via the cosmological constant.[/quote]
All this does not preclude exotic theories that may propose a different interpretation of DE and DM. Whose to say that someday the essence of these things might understood, but much work is needed to bring those theories to be accepted and successful as GR is now.
[quote="ErnieM"]
How is dark matter converted into dark energy? [/quote]
DM and DE are not necessarily correlated, at least in the sense the one is, or can be, converted to another. Keep in mind that DM and DE are apparent entities that are not understood, but manifest themselves in comological observations and supported by GR (Lambda-CDM) model. Also, the concept of an expanding Universe was a direct consequence of GR, whence the origin of Lambda ([url=http://en.wikipedia.org/wiki/Cosmological_constant]Λ[/url]) the cosmological constant. It is interesting that DE and GR have an apparently intrinsic connection, but DM is not born from GR. Thus it seems reasonable, today, that DM and DE are viewed as distinct, uncorrelated, entities despite not knowing what they really are.
[quote]Does dark matter follows Einstein's E = mc[sup]2[/sup]?[/quote]
I think it's fair to say that since DM can be effectively mapped / modeled by gravitational lensing and stellar velocity distributions (e.g. within a galaxy), and the observed gravitational effects on its surroundings are not distinguishable from that due to baryonic (normal) matter, the idea of DM and energy equivalence is valid. However, applying Einstein's energy equivalence to DE does not make sense. DE / Vacuum Energy imply a repulsuve gravitational field.
[quote="[url=http://en.wikipedia.org/wiki/Vacuum_energy:gyv0t0nw":313eeha8]Wiki[/url]"]The vacuum energy also has important consequences for physical cosmology. Special relativity predicts that energy is equivalent to mass, and therefore, if the vacuum energy is "really there", it should exert a gravitational force. Essentially, a non-zero vacuum energy is expected to contribute to the cosmological constant, which affects the [color=#0040FF]expansion of the universe[/color]. In the special case of vacuum energy, general relativity stipulates that the gravitational field is proportional to ρ-3p (where ρ is the mass-energy density, and p is the pressure). Quantum theory of the vacuum further stipulates that the pressure of the zero-state vacuum energy is always negative and equal to ρ. Thus, the total of ρ-3p becomes -2ρ: A negative value. [color=#0040BF]This calculation implies a repulsive gravitational field, giving rise to expansion[/color], if indeed the vacuum ground state has non-zero energy. However, the vacuum energy is mathematically infinite without renormalization, which is based on the assumption that we can only measure energy in a relative sense, which is not true if we can observe it indirectly via the cosmological constant.[/quote]
All this does not preclude exotic theories that may propose a different interpretation of DE and DM. Whose to say that someday the essence of these things might understood, but much work is needed to bring those theories to be accepted and successful as GR is now.