Did Antimatter Annihilate Matter During the Big Bang?

[Quds Akbar]

The law of conservation of matter and energy does not apply to the creation of the Universe. What you are doing by assuming that there was time before the Big Bang is like saying that there is a more south point than the most South point on a circle without flipping or turning its orientation. It doesn't work that way, that's what makes the "what banged" in the Big Bang so challenging. You're idea however might work if there was a Multiverse and matter could exist between Universes. However, it is a good way to go beyond that like you did, that is what I do not like about the Big Bang.

 

[timmdeeg]

Honestly I think that this view fails before it even gets started for the simple reason that we know of common particles that are their own anti-particles: photons. The only way to fit photons into this pictures is to make it so that they do not generate any gravitational field at all. And making it so that photons generate no gravitational field would rather drastically alter the expansion of our universe at very early times, almost certainly resulting in dramatically different BBN predictions.

Ok, this is a very convincing point, so my scenario seems purely fictional. Even so, I have a question.

Basically this means that anti-matter picks up a minus sign for its mass when it occurs in the gravitational force, but still has a positive value for the mass when considering acceleration.

Why "but still has a positive value for the mass when considering acceleration"? Isn't $F=-ma$ then?

This would mean that an anti-matter universe would behave, gravitationally, exactly like a matter universe. But if you had two clumps of mass, one made of anti-matter and the other made of matter, then they would gravitationally repel one another.

Understand, thanks. So, a universe filled with with anti-matter (minus sign for the matter) wouldn't imply that the matter density is negative, right?

 

[Quds Akbar]

Ok, this is a very convincing point, so my scenario seems purely fictional. Even so, I have a question.

Why "but still has a positive value for the mass when considering acceleration"? Isn't $F=-ma$ then?

Understand, thanks.

I did not understand the question properly, could you please paraphrase it. I also did think of it that way, until I saw that diagram in a book. However I do stress that this idea may be considered and would be considered since the fact that a multiverse exists could be a possibility, which is what your theory is based on. But that is a very good perspective to look at it.
Thanks

 

[Torbjorn_L]

The law of conservation of matter and energy does not apply to the creation of the Universe.

Similarly, 'creation' or emergence wouldn't apply in such a case. The universe would just be. (E.g. no-boundary topologies work.)

But that depends on what you mean by "the Universe". The Hot Big Bang, where matter emerged and baryogenesis happened, emerges out of inflation. If inflation is eternal and consists of a multiverse, does the term "universe" apply? And how does it work? And what would it say on matter/antimatter asymmetry?

The OP would be answered with the idea of baryogenesis and the observation that it isn't obviously wrong (and very nearly good enough as of lately).

 

[Chalnoth]

Why "but still has a positive value for the mass when considering acceleration"? Isn't $F=-ma$ then?

Well, what you'd do is have two masses for an object: m_i and m_g. For normal matter, m_i = m_g. For anti-matter, m_g = -m_i. The inertial mass, m_i is always positive. The term m_i appears in the acceleration equation, while m_g appears in the gravitational force.

Understand, thanks. So, a universe filled with with anti-matter (minus sign for the matter) wouldn't imply that the matter density is negative, right?

The gravitational matter density would be negative in that case, yes.

 

[timmdeeg]

The gravitational matter density would be negative in that case, yes.

And therefore would behave like a cosmological constant, gravitationally repelling(i). But that's confusing, because as you said, an anti-matter universe shouldn't be distinguishable from a matter universe. So, perhaps (i) is wrong or anti-matter doesn't mean negative mass, or something else?

 

[Chalnoth]

And therefore would behave like a cosmological constant, gravitationally repelling(i). But that's confusing, because as you said, an anti-matter universe shouldn't be distinguishable from a matter universe. So, perhaps (i) is wrong or anti-matter doesn't mean negative mass, or something else?

A cosmological constant acts very differently. In Newtonian terms, it's effectively like adding an extra term to the force equation:

F = G m_1 \left(-{m_2 \over r^2} + {\Lambda r \over 3}\right)

This is the force of mass 2 on mass 1 (so the cosmological constant adds a pure acceleration term of any two objects away from one another).

 

[timmdeeg]

A cosmological constant acts very differently. In Newtonian terms, it's effectively like adding an extra term to the force equation:

F = G m_1 \left(-{m_2 \over r^2} + {\Lambda r \over 3}\right)

This is the force of mass 2 on mass 1 (so the cosmological constant adds a pure acceleration term of any two objects away from one another).

Yes, I understand, but instead had the Friedmann term $(\rho c^2 + 3p)$ in my mind. As we agreed that the gravitational matter density $\rho$ is negative, it should act repelling, like negative pressure. On the other side a cloud consisting of particles with negative gravitational mass each, should gravitate attractive due to the acceleration law (because of $m^2$). So, there must be a severe misconception. I suspect, I can't interpret the Friedmann term in that way and it would be great, if you could help me out.

 

[Chalnoth]

Yes, I understand, but instead had the Friedmann term $(\rho c^2 + 3p)$ in my mind. As we agreed that the gravitational matter density $\rho$ is negative, it should act repelling, like negative pressure. On the other side a cloud consisting of particles with negative gravitational mass each, should gravitate attractive due to the acceleration law (because of $m^2$). So, there must be a severe misconception. I suspect, I can't interpret the Friedmann term in that way and it would be great, if you could help me out.

I think you'd have to re-derive that equation with the new mass concept. I'm not entirely sure how it would turn out. I think it could be done in a consistent manner, but I'm not sure.

 

[timmdeeg]

I think you'd have to re-derive that equation with the new mass concept. I'm not entirely sure how it would turn out. I think it could be done in a consistent manner, but I'm not sure.

Or, perhaps, there is a real contradiction, revealing that the conjecture to assign a negative gravitational mass for anti-matter is unphysical.

 

[Nuradh]

How is mass defined at the current moment?
Is it the result of attractive forces or the result of how we weigh it or perhaps of how the matter interacts with gravitation?

In case it is the result of attractive forces it will remain positive even if it is perhaps anti-matter.
In case it is the result of interactions with gravitation is will change depending on whether or not the antimatter falls towards Earth or remain still(moves away perhaps)
if it is the result of how we weigh it... Gravitation, for all the fun people out there.

Sorry if this is an unwanted reply

 

[Vanadium 50]

Can we stop talking about negative gravitational mass? It's been brought up at least twice that this is a non-starter because it disagrees with data.