World Science Scholars

3.4 Loop Quantum Gravity

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    • Does it make sense to you that a set of equations describing the structure of spacetime would not include a time variable?

    • It makes sense that the equations do not contain a time variable within the context of loop quantum gravity as Prof. Rovelli explains it. The granualarization of spacetime seems to negate the need for a time variable at the planck unit scale.

    • To replicate GR or even SR, it should be possible to derive from the equations that time is also quantised at the same level, thus although it is the area of foam cell boundaries that takes discrete values, those should be seen as equally products of Planck lengths or with Planck times. In GR there is no preferred frame so we cannot say whether any area boundary is spatial or temporal, they are not inherently distinct.

    • I think that time is not fundamental …. at least not a dimension equivalent to the 3 dimensions of space… it is relative to some cycle… either in Caesium or in the solar system… what is the definition of a second.. the time taken for some specified transitions in caesium… THOSE TRANSITIONS DEFINE A SECOND, THEY ARE NOT CAUSED WITHIN A SECOND…

      SORRY😅😅😅STILL AN UNDERGRADUATE…

    • Yes, I think that the time is a label that describes a cronological order of events, but this order is not fundamental. In the probabilistic view (second law of th.) the entropy grows as the time goes on, but this assertion is statistical only. In a fundamental way, we can not build a clock to stablish a temporal order in the cosmos. But this label is usueful when we split the behavior of systems in order to describe them. The dynamical systems are good examples of these.

    • It makes sense to me because for example, when we calculate distance using speed and time, we didn’t actually use a distance variable. There may also be other ways that we could calculate distance using distance variable.

    • I guess time is emergent, just like space, and both of them are probably just a way of describing the relationship between some “fundamental nodes” of reality. It could be that fundamentally the quantum fields (or whatever their ontology is) are “what’s real” and then if you describe their relationship (for example as a measure of entanglement) then you end up with what we classically call space and time.

    • Yes. I believe that ‘time’ is a local property (of the quanta) because when LQG quanta interact there is a before-interaction-after. This means that there is a causal relationship (in the interaction). To be shown is how ‘time’ as we know it emerges from local time.

    • I am not sure that time as it is popularly understood is very relevant.
      I get into a car at at home and wake up somewhere else – just two events that relate as a sequence – however the driver of the car experiences many more sequential events over the same journey. Time would be perceived very differently from each of these perspectives… But causality would still be maintained.

    • Stated before, time is emergent, not fundamental. It is not in gravitational equations.

      So the semantic of the word spacetime becomes only space.

      This does seem a divorce.

    • Time is not required for what the math is describing so no not necessary.

    • In the context of Loop Quantum Gravity (LQG), it does indeed make sense that the equations describing the structure of spacetime do not include a separate time variable in the same way that classical physics or general relativity do. This feature is a fundamental aspect of LQG and is known as the “problem of time.”
      In LQG, spacetime is discretized into discrete units, and the theory describes the quantum properties of these discrete structures. Unlike classical physics or general relativity, where time is treated as an independent and continuous parameter, LQG treats time differently. Time, in LQG, is typically treated as an emergent concept rather than a fundamental one.
      One of the key insights of LQG is that the equations of the theory are formulated in terms of certain operators that act on quantum states, such as the Hamiltonian constraint operator. These operators encode the dynamics of the theory and govern how the quantum states of the discrete spacetime evolve. However, these operators do not have an explicit time variable in the same way that classical Hamiltonians do in classical mechanics.
      Instead, LQG incorporates the concept of “evolving relational observables.” These observables represent the relative relationships between different parts of the quantum spacetime. They describe how one part of the quantum geometry is related to another part and how these relationships change over “time.” In this sense, time is defined through the relationships between these observables, and it emerges from the dynamics of quantum geometry.
      This approach to time in LQG is quite different from the classical notion of time as an absolute and independent parameter. It reflects the fact that in a quantum theory of gravity, the structure of spacetime itself is expected to undergo quantum fluctuations and changes at the smallest scales, which challenges the traditional notion of time as an external and unchanging background.
      So, in summary, it makes sense in the context of Loop Quantum Gravity that the equations describing the structure of spacetime do not include a separate time variable, as time is treated as an emergent concept arising from the relationships between quantum observables rather than a fundamental and independent parameter.

    • Perhaps gravity is most relevant on the larger scales, however, time may not be an essential component of emergent gravity.

    • Observing that at the quanta scale, spacetime is nonexistent and immaterial. This would make sense to not be included in calculations.

    • Great

    • Tal y como el espacio es un factor emergente no elemental a primera instancia, el tiempo tampoco lo es, y podría tener sólo importancia en fenómenos que puedan dar cuenta del carácter irreversible de su paso: el tiempo desde el punto de vista término y entrópico. Considero que sólo desde el punto de vista de la termodinámica el tiempo sería una variable indispensable en las ecuaciones fundamentales, y sólo si diera cuenta del claro paso de estados o de información disponible en el sistema.

    • Ladies and Gentlemen,

      From Arthur we have this :

      “The granualarization of spacetime seems to negate the need for a time variable at the planck unit scale.”

      From Anthony, we have this:

      “Observing that at the quanta scale, spacetime is nonexistent and immaterial. ”

      These are not topics that can be ignored, so from the tie- together Schmidt Paradox we have it that time’s arrow has the place in the large, relativity science.

      With the Quantum allowance for multidirectional time in the Schmidt Paradox, we can hear the SETI talk about how they do not know what time it is. They have minimized into their vessels into the Quantum area.

      The supporting statements above for a recognition of a time alteration allows that time occurs separately in the Quantum region.

      White Holes give us a remake science, or a more indepth science. We need to however question if the black hole science is accurate.

      SETI Huk can live inside areas we call black holes. They retrieve the smaller black holes into their supermassive dwelling areas. Mid- sized black holes at galaxy gravity centers are also dwellings. SETI Huk does not inhabit the individual small round appearance black holes.

      In consciously designing the approximate 10% green galaxies for organic life, SETI Huk is vastly missed in scientific discussions.

      In Canada, the aboriginal population bait and pull SETI Huk from the Sea of Dirac transits. And others under NASA lifeform protection.

      If we wish to have a better galaxy or Earth, the SETI baiting and eating by non- humans needs to end.

      Canada is a difficult place to stop that, as is Russia due to the cultural pretenses of SETI populations. Both have demographics similar for similar responses.

      White holes are a topic here and if i have wrongly posted to Prof. Rovelli’s place, i apologize. World politics do not need to scare friendly SETI from Earthers blame for killings.

      What type of rights are those?

      The latest WSF talk allows that there has been a black hole calculated for a near 🔱 Ŋeptuŋe location. SETI Huk will either clear that or be using it purposefully.

      Our sciences need updating, and Trump budgetary requirements may allow new topics, instead of generational waiting for new science.

      http://www.monroeinstitute.org

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