[nilak (OP)]

One possible time structure is the one in which the present is real but the past and the future do not exist anymore or yet. This case clearly does not allow time traveling, by definition.

The other option is that past, present and future all exist. This means everything is already recorded. If this is the case, you can't travel either, because it would require changes in the past or future which cannot take place since will contradict the definition of the past, present and future being already written. If it's changing means it wasn't written yet.

Usual discussion about time allow a combination of these options which, to me is nonsense.

A possibility of traveling faster than light aslo leads to question whether we can go back in time by doing so. However the speed of light c in the Lorentz transformation is by definition the fastest. In fact, this is the causality speed and motion is generated by it. Its like saying, " can the domino pieces wave travel faster than individual falling pieces?" No because each piece has to wait for the previous to fall. To travel faster you need a faster causality  speed. This is possible, but in that region light also travels faster because of the faster causality. Then, of course, accelerating at c require an infinite amount of energy by applying relativity.

[yor_on]

There are some ideas of what the past, the now, and the future, might be. Some people thinks we always are in the 'now. Others think that the future depends on fuzziness. becoming more fuzzy the longer you extrapolate, with the opposite reaction being that your 'past' becomes questionable. The past is 'questionable' but that doesn't depend on 'time' per se. that depends on those keeping records of it. We tend to mix what we are, 'humans' with what we think the world to be.

[yor_on]

What I mean is that even with observer dependencies ruling this universe, we expect there to be a logic. If that logic holds then your past should hold, even if you fail to define it perfectly. The logic becomes what we define as our 'common universe'. lose that, and then lose sight of a universe

[yor_on]

The point with a 'fuzzy' logic, where there only is a 'now' is that you really need to stop talking about 'physical laws'. whatever makes you think they exist. Statistics?