Negative Mass: Possibility of FTL Travel?

[pmb_phy]

But what is the pressure a function of?

I wish I knew. I'd be rich!

You're saying the physicists who wrote that article are wrong, and that it's not possible to have negative pressure with a positive energy density?

No. That is not what I'm saying. The active gravitational mass density = energy density + 3*pressure (c=1). For the the active gravitational mass to be negative you must have


energy density + 3*pressure < 0

So the energy density can be positive and if the pressure density is far enough into the negative then it will overwhelm the energy density and make the active gravitational mass density negative.

Pete

 

[JesseM]

No. That is not what I'm saying. The active gravitational mass density = energy density + 3*pressure (c=1). For the the active gravitational mass to be negative you must have


energy density + 3*pressure < 0

So the energy density can be positive and if the pressure density is far enough into the negative then it will overwhelm the energy density and make the active gravitational mass density negative.

Pete

Ah, thanks, I hadn't caught the distinction you were making between the energy density and the active gravitational mass. So in the case of dark energy, it's thought that the pressure is negative while the energy density is positive, which I guess would mean the active gravitational mass could be either negative or positive depending on the balance between them.

 

[pmb_phy]

Ah, thanks, I hadn't caught the distinction you were making between the energy density and the active gravitational mass. So in the case of dark energy, it's thought that the pressure is negative while the energy density is positive, which I guess would mean the active gravitational mass could be either negative or positive depending on the balance between them.

Yup. In a vacuum domain wall the active gravitational mass is negative. For an infinitely long straight cosmic string the active gravitational mass is zero!

Pete

 

[taylaron]

aside---
a negitive mass object would revolutionize weight limmited objects such as aircraft and many many other applications.
this would definitely be usefull. if we can produce a working model though,
until then... happpy theorizing...
you'll never fully know if it will work until you actually do it.

 

[pmb_phy]

aside---
a negitive mass object would revolutionize weight limmited objects such as aircraft and many many other applications.
this would definitely be usefull. if we can produce a working model though,
until then... happpy theorizing...
you'll never fully know if it will work until you actually do it.

That there is a negative active gravitational mass at work in the cosmos cannot be taken to imply that it can be applied to a finite body. No hovercrafts on this account.

Pete

 

[heskam]

imaginary fields

Why can't we dualize our "physical" world?
For example imaginary gravitational field would (in my thinking) produce attraction with equal signs and repelling with opposite signs.

Still there might be some "covariance" between real ("physical") and imaginary worlds: if a mass is imaginary then it would produce real positive effetcts by
-im * iField. That would connect dualities to real world and physics.

If we accept dualization principle we could accept negative or imaginary time also.

Or if there were negative masses why should they be here?

So Occams razor wouldn't work with consistent extensions?

If you have a singular point then you can:
a) Try to find a topological compactification.
b) Try to find an topological identification.
c) Try to remember that two finite dimensional spaces can intersect in a point, line, etc.
d) something else.

 

[heskam]

it is imaginary, meaning it has no physical meaning.

How can you say that a point has physical meaning?
I would put at least equal mass for i as for a point.

Wiki:
"Spontaneous symmetry breaking describes the case where the laws are invariant but it appears the system isn't because the background of the system, its vacuum, is noninvariant. Such a symmetry breaking is parametrized by an order parameter. A special case of this type of symmetry breaking is dynamical symmetry breaking.
"

Could we use that for a cosmological constant?
Then if you remove the point of singularity, there might be i times gravitational field lurking through that hole.

 

[henryco]

Hello,

I have another question related to negative energy rather than negative mass.
If my understanding of QFT is correct and as far as i can check in a reference QFT book as Weinberg's one, the negative energy quantum field (creating and annihilating negative energy quanta) should be an equally acceptable solution of all field equations as is the positive energy quantum solution. Only the latter is retained because of instability issues and because these remained undetected so far but isn't it illicit to reject half of the possible solutions by hand? Shouldn't this be considered as a serious remaining open issue in physics ?

Rem:
- antiparticles cannot be considered as the solution to the negative energy issue after second quantization.
- Although antiunitary time reversal avoids the time reversal regeneration of negative energy states, this is not sufficient to discard them if we have realized these are equally acceptable solutions of all field equations as the positive ones.


Fred

 

[SdogV]

Re: Heskam's 1/22/08 note (above) ( and http://www.negative-mass.com/ )
Given: ("KISS" © Physics)
(1) gravitational force law, F is proportional to product of masses divided by distance between squared
(2) Mass 1 plus mass 2 = 10
(3) Distance between is 1.
(Note "duality" about F = 0 )
M 1 M 2 Force
5 5 25
6 4 24
7 3 21
8 2 16
9 1 9
10 0 0
11 -1 -11
12 -2 -24
13 -3 -39
14 -4 -56
15 -5 -65

Do you see anything unusual about this data?
(Hint: I am seeing chemistry! ??)