What is the basis for the existence of anti-matter other than the negative energy solutions of?

Question

the Dirac and Klein-Gordon equations.

Dirac in the 1930s advanced the hypothesis that not just the electron, but all particles known at the time have antiparticles. But his reasoning was incorrect, as I understand it, and he later acknowledged that he was influenced by "peer pressure" (although he was no longer a teenager at the time), which consisted of a negative atmosphere for the introduction of more particles. He therefore hypothesized that all particles were representations of the same unitary group. Hence the existence of antimatter.

That argument no longer being viable, what is the modern argument?

Answer 1

So what are you asking exactly?  For experimental evidence that an antiparticle is itself a particle rather than a hole in the Dirac sea of filled negative energy states?

The only evidence I can think of would be gravitational in nature--the Dirac sea would have implications for a cosmological constant.  But you can hand-wave that away in various ways (the modern interpretation requires similar hand-waving).  The worst thing about the Dirac sea is just that it's god-awful ugly.  I can only imagine trying to do QFT and trying to keep track of all those sea particles.

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Gravity is weak, but in principle, it matters.  The Dirac sea would have implications for the vacuum energy (EM energy if I must say so at the risk of bringing trolls into the discussion), which would give you a cosmological constant.  But any approach has infinite energy issues, and you can resolve them.  So you can't answer your question that way.

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I don't understand how you say the Dirac sea interpretation or the anti-particle interpretation don't work for neutrinos or mesons?  Which one do you think won't work?  The dirac equation applies to all spin-1/2 particles.  That includes neutrinos.  A neutrino and an anti-neutrino can, in fact, annhilate one another.  This can only happen through the weak interaction, however.  So you need to have the neutrino and the anti-neutrino with enough energy between them to annhilate into a Z (or a virtual Z that decays into a pair of leptons).  They aren't charged so they don't couple to photons.  That also means they don't attract each other enough to form a bound state like positronium as e+ e- do and do the little dance that can be the precursor to annhilation.  And the weak coupling is just ridiculously small anyway.  Anyway, while you shouldn't try to look for neutrino annhilation, it happens in theory.

As for scalar (spin 0) mesons, you got it correct--the KG equation applies.  For the vector mesons (spin 1), it's the Proca equation.  Some particles (photons and Z, for example) are their own anti-particles.

----I think the bottom line answer you're looking for is that Dirac's original interpretation isn't necessarily wrong.  It's just not as useful as others for doing problems.

Since you seem to be more of a solid state guy, let's talk about electrons and holes in semi-conductors.  It would be a god-awful mess to keep track of all the electrons.  It is a million times easier to treat the "holes" as particles in their own right.  Does it really matter whether or not those holes are real?  You treat them as particles and get the right answer.  Now in solid state, you could theoretically have the luxury of looking closer and seeing that the holes are, in fact, missing electrons and not real particles.  But in particle physics, we don't have that luxury.  These are fundamental particles--you can't look any closer.  So philosophically, the question of which interpretation is "correct" is moot.  We use the one that is most convenient that lets us calculate easiest the things we observe in experiments.

Answer 2

What do you mean "modern argument?" Antimatter is an observed fact.

Answer 3

Once speculated researchers looked for them in high energy accelerators..  Particles with the masses of protons and electrons but with the opposite charges where found.  They annihilated the normally charged protons and electrons releasing the predicted energy bursts, so confirming there existence. The modern argument is "simple" experimental proof fitting hypothesis.

Answer 4

There is no 'basis' for the existence of anti matter, it is merely the way it happened. Today it is accepted that from the singularity a small excess of matter was created over that of anti matter, when the mutual annihilation of the opposite particle took place we were left with ordinary matter.