Tachyons

[Claudio Marchesan]

I everyone:

This thread starts from: https://forums.space.com/threads/implications-of-a-closed-universe.70399/post-615312 and the replies after this one. I agree with Gibsense: we can only hypothesize extra dimensions, not see them. But compact rolled-up dimensions are an idea that comes directly from String Theory.

Let me restart by saying that we can talk about tachyons because arXiv, the official scientific archive (with very strict rules), contains publications on the subject. But to formulate a conjecture, it would be necessary to delve into String Theory, with its compact dimensions, and master quantum mechanics. As far as I'm concerned, I don't have enough skill to deal with the topic. If interested, we could at least discuss our ideas.

Speaking of tachyons, I've come across two different formulations that deserve attention:

Tachyons and Relativity: Some studies explore the possibility of tachyons by extending the concept of causality without drastically altering special relativity, while others even assume a “Preferred Frame”.

Compact Dimensions and String Theory: In this context, the publications do not explicitly mention tachyons but focus on quantum non-locality with the aim of preserving the principle of causality.

We can summarize the situation in String Theory regarding tachyons and compact dimensions in this way:

Tachyons:

• Tachyons, hypothetical particles with imaginary mass and speeds exceeding that of light, were present in the early formulations of bosonic string theory.
• However, their existence created problems of causality and instability in the theory.
• In the more modern versions of string theory, such as superstring theories, the introduction of supersymmetry has allowed for the elimination of tachyons, resolving these problems.
• Therefore, tachyons are no longer considered an integral part of current string theory.

Compact dimensions:

• Compact dimensions, on the other hand, remain a fundamental element of string theory.
• The theory requires the existence of extra dimensions, beyond the four dimensions of spacetime that we know (three spatial and one temporal).

A question arises spontaneously: could these "shortcuts" be used by tachyons? Although modern Superstring Theory does not predict tachyons, the possibility that they could exploit compact dimensions to move between distant points in space-time remains a fascinating hypothesis.

At present, the only confirmed form of non-locality is the quantum one. In his book “The Undivided Universe, Bohm (whose Pilot Wave I greatly appreciate) proposed an interpretation of the Entanglement that preserves the principle of causality. As an engineer, when I think of "everything being interconnected," I can't help but associate it with the dynamics of a rigid body. Even within a body, stresses propagate at speeds lower than light, so the idea of a unified universe does not solve the problem for me.

There is only one way to think about causality: if complex dimensions exist, only tachyons (understood also as yet unknown forces like Bohm’s Pilot Wave) can traverse them. Thus, causality depends on the path connecting two events, and the ability of the tachyon to carry the information we need.

I am citing article: arXiv:quant-ph/0204002]: Parity Violation and a Preferred Frame for completeness. It discusses neutrinos, I read it (without adequate skill) because I was hoping to introduce the question: Can the Neutrino, with its very light mass, enter a compact dimension with the tunnel effect?

But the article is very far from addressing that. From what I gather, the author questions whether a change in the inertial reference frame could invalidate certain results in weak interaction research. The idea of the neutrino as a tachyon is speculative: here it attempts to address the helicity reversal under a Lorentz boost by hypothesizing the existence of a "Preferred Frame", which would call into question our measurement.