Ah.. the speed of lite (light)

[paultrr]

The main issue why this is even being studied and debated is because we general measure distances out there based upon the value of C and some other factors. If C does change with time then our measurements might be off.

[Bo]

it should be noted that not all inflation models require a false vacuum. and also perhaps the term vacuum should be cleared here: what this is all about is a particle, which we call the inflaton, that, when certain conditions are met, causes the universe to expand. inflatons are equally spread across the entire universe. The inflaton has a certain energy, and this energy decides wether we have inflation or not.

 

But my point here is on the speed of light; First the more simple point; for the universe to be electricly neutral (which according to our best understanding is the case), the inflaton field also should be -on avarage at least- neutral. So a change in the inflaton vacuum wouldn't change the e/m properties of the vacuum and therefore don't change the speed of light. BTW this doesn't mean that other vacuum properties CAN change over time and CAN influence the speed of light; i just think that the inflaton isn't the right choice.

Second: the speed of light doesn't change as the scale factor of the universe changes, because the speed of light is defined with respect to that scale factor. In other words; if the notion of a meter schanges, the notion of speed (meter/second) also changes accordingly.

 

Our current vacuum state is considered generally as stable

Well, not quite, in string theory some billions of zillions of possible vacua are possible. Thus -unless it is correctly understood why we live in this vacuum, it is tempting to think that are vacuum is only meta-stable (like a marble on a hilltop)

 

 

Sorry for all the annoying questions. = )

Asking questions is the beginning of all good research, so don't apologize!

 

Bo

[paultrr]

Yes, some of the String theory based speculation on the end state of the cosmos in conjunction with the observed accelerated expansion centers upon it being possible for our vacuum to decay eventually. All of this is basically, theory at the present including the possibility that C has slowed down. Its also true the ZPF is from what we can tell electrically neutral. Using PV the actual reason it might alter is different from that incountered with normal inflation theory. Charge there does not cause a change at all. Generally, its a lot of different aspects involved in the stress energy tensor that are changing under such modeling.

 

Here is one aspect in relation to dark matter and exotic energy in the cosmos. By observation whatever both are they seem to be strongest outside of regions with a lot of matter/energy present. Under some versions of PV the exotic energy is simply a region with higher vacuum pressure than regions with more matter/energy present have. The slowdown there would be a vacuum pressure difference. An intertesting aspect out of the more common version of PV most put forward is that in theory C should be speeding up, not slowing down. I have a friend of mine who takes that common position and we have argued a bit over this. However, he admits he has studied the cosmological observations very little and his model could be turned around to account for a slow down also. Personally, as I told him also the evidence out there at present could be interpreted to either support C stays constant or it slows down.

[paultrr]

A lot of us tend to suspect its energy density and not charge itself that alters the vacuum. I agree charge has absolutely no effect on cosmic scales in general. However, as far as the cosmos goes this does ot imply that its energy is actually increasing. Its simply that as the universe formed regional differences became built into its structure. Those differences allow vacuum energy to be different from region to region. The accelerated expansion simply becomes a by-product of an inflation process driven by higher vacuum pressure in regions where matter was less dence to begin with.

[Bo]

A lot of us tend to suspect its energy density and not charge itself that alters the vacuum. I agree charge has absolutely no effect on cosmic scales in general. /QUOTE]

 

ah great; then we agree B)

 

Bo