## Some reflections

It is a lot of time that I am thinking about the scenario is emerging from our current understanding of reality through physics. There is a lot to be understood yet, mostly the very nature of space and time and a proof of the real number of dimensions our universe emerged from. Notwithstanding these noteworthy missing questions, we can make an idea of what is going on as the depth of our understanding is already quite sensible.

At the dawn of the last century, Albert Einstein put forward an important conclusion: mass and energy are the same thing. Indeed, what Einstein had in mind is a deeper understanding of the concept of mass that is for us an important concern. Where does mass come from? What is it made of? At the start of the last century these questions could not have a proper answer. But having reduced the mass to another concept, like energy, was of paramount importance.

On a similar ground it was relevant to understand the role of another, apparently not reducible, concept: Charge. Today we know that the number of charges, the couplings that make all change around us, will be at last reduced to a single number. Maybe. So far we only know for certain that, thanks to Steven Weinberg, Shelly Glashow and Abdus Salam, we have reduced the number of interacting fields. But strong coupling and gravitational constant are still there disconnected if we limit to our current experimental knowledge. Of course, theoretical physics has gone really far in this area and we hope that LHC will help us to give a way to cut out most of what was done here to get the real understanding of the way things work. Somebody will be happy others won’t but this how our World works.

Today, we have a better understanding of the concept of mass and, while waiting for LHC to confirm us our ideas, we can draw some conclusions about all these questions. The fact that mass is energy is an important clue of the idea that this concept is reducible to more fundamentals concepts and that a mechanism for its emergence must exist. Higgs mechanism goes in this direction as also our ideas emerging from QCD about the mass gap that confirm the idea that mass is not a fundamental concept by itself.

So, we can conclude that, so far, our ideas of the World reduce to two fundamental non-reducible ideas: Energy and charge. The former is just a safety lock with respect to the changes provoked by the latter. So, I leave you with a final question: If things stay in this way, does space-time entail a wider concept to embed them or we can reduce also this to them?

### 9 Responses to Some reflections

1. Anonymous says:

shouldn’t one realize that energy-momenta is the charge carried by local space-time translations, and that gravitation is the gauge theory of diffeomorphism invariance? This makes energy reducible to charge, an idea that is known for a while.

2. mfrasca says:

Dear Anon,

Not really. You are just renaming different things with the same names. Let me explain what I mean. Suppose you have a massless self-interacting field theory producing a dispersion relation

$p^2=\mu^2\sqrt{\frac{\lambda}{2}}$

being $\mu$ an integration constant having dimension of energy and $\lambda$ the coupling of self-interaction. You can see that mass is obtained through the coupling of the theory and you have got a real understanding of the way mass is obtained. So, mass is a derived concept.

In your case, there is currently no understanding of the way space-time could be reduced (here I forget about theoretical proposals around and limit myself to well-acquired knowledge) and so I do not know how the Newton constant could be related to it. Finally, so far we have yet to acquire a knowledge of the way all the couplings are related each other and this surely will entail a deep knowledge of the way our current view of space-time emerges.

Marco

3. […] seen that mass is a derived concept and not a fundamental one. I have given an explanation of this here. In a Yang-Mills theory, massive excitations appear due to the presence of a finite nonlinearity. […]

4. Ulla says:

there is currently no understanding of the way space-time could be reduced…

What about ’emergent’ spacetime then?
Could it just turn invisible to us?

• mfrasca says:

Dear Ulla,

It is also my conviction that space-time as we observe should be considered emergent. What seems rather striking in quantum gravity studies is that the background from which space-time emerges is just 2-dim. The strongest proposal so far displaying such a characteristic is just string theory. The main point to be answered is what makes space-time much in the same way people at the end of ‘800 asked what we are made of and solved the question trough the discovery of atoms and the understanding of their behavior in the following years. What helped them a lot was the large quantity of experimental data to explain that addressed people on the right track. Today we are in a situation where there are a lot of proposals, more or less credible, but very few or nothing experimental results to support them or to address us correctly.

My personal view is that I am waiting for LHC results. In the case supersymmetry will finally come out, and I am forced to be a supporter of supersymmetry, string theory will be finally boosted as the only proposal nearer to truth. Supersymmetry is a need for string theory and come out from it. This discover will be an epochal one.

Cheers,

Marco

5. Ulla says:

Supersymmetry cannot be the only one, it lies in its charachter. Infinite possibilities, but what determines the facts, the reality? We shall wait for LHC. The evidences so far is not in faviour of SuSy, as I can see.

Time and consciousness determines the criticality?
http://arxiv.org/pdf/1011.5861
Today’s analysis looked for a gluino, which is the gluon’s supersymmetric cousin. As if this weren’t exotic enough, this analysis looked for very long-lived gluinos, potentially existing for more than 15 minutes. In a field in which a lifetime of a millionth of a second is a long time, 15 minutes might as well be forever.

http://arxiv.org/abs/0901.4117

• mfrasca says:

Dear Ulla,

What I expect to see is a Higgs sector to display supersymmetry. This should be the starting point to understand the rest. Thank you for the link to the preprints.

About what forms reality, here the question can be turned into: What makes a wave-function collapse? While I have ideas about, and many of my readers could know them, I would not like to enter in such a critical matter at this moment. You can read some of my older posts if you like.

Cheers,

Marco

6. Ulla says:

Another good question is, the two forms of matter, living and ordinary, and how the collaps differ. It is like living matter has two forms of wavefunctions at the same time, both quantum and classical, and they can live together in the measurement, so there may be no collaps? Scrödinger cat is both dead and alive, because it has two ‘bodies’. There the time and consciousness enter the picture.

I have read some of your texts, thank you. What makes a wavefunction collapse, or the decoherence, is one big question forming reality, and it seems the scaling problem is essential. Also ways to keep the topology or entanglement, although a measurement happen.

From what is spacetime emergent? Which bricks are used?

• mfrasca says:

Dear Ulla,

I do not know what the bricks of space-time are. I would like to have an answer to this question but I have not. String theory says that these are small chords while loop quantum gravity uses spin networks but there are also other proposals. So far, we have no experiment to guide us toward such an understanding and we are back to my previous answer: I am waiting for LHC to help us in some direction.

Cheers,

Marco