On Mon, Oct 19, 2020 at 3:33 AM Jason Resch <[email protected]> wrote:
> On Fri, Oct 16, 2020 at 6:19 AM Bruce Kellett <[email protected]> > wrote: > >> On Fri, Oct 16, 2020 at 5:49 PM Jason Resch <[email protected]> wrote: >> >>> On Thu, Oct 15, 2020 at 6:07 PM Bruce Kellett <[email protected]> >>> wrote: >>> >>>> On Fri, Oct 16, 2020 at 9:51 AM Jason Resch <[email protected]> >>>> wrote: >>>> >>>>> I noticed that Victor Stenger's position on entropy, as described >>>>> here: https://arxiv.org/pdf/1202.4359.pdf on page 7, appears to be >>>>> the same as described by the cosmologist David Layzer in a 1975 issue of >>>>> Scientific American: >>>>> https://static.scientificamerican.com/sciam/assets/media/pdf/2008-05-21_1975-carroll-story.pdf >>>>> >>>>> The basic idea, which is described graphically here: >>>>> https://www.informationphilosopher.com/solutions/scientists/layzer/arrow_of_time.html >>>>> >>>>> It is a counter-argument to the commonly expressed idea that the >>>>> universe began in a low entropy state. Rather, it explains how the >>>>> expansion of the universe increases the state of maximum possible entropy. >>>>> If the universe expands more quickly than an equilibrium can be reached, >>>>> then there is room for complexity (information / negative entropy) to >>>>> increase. >>>>> >>>>> Why is it that the "low entropy" myth is so persistent, and this >>>>> alternate explanation is so little known? Some physicists, such as Penrose >>>>> are still looking for alternate explanations for the special low entropy >>>>> state. What fraction of physicists are aware of Stenger's/Layzer's view? >>>>> Does it appear in any physics textbooks? Has it been refuted? >>>>> >>>> >>>> It is refuted by the idea of unitary evolution in QM. Unitary evolution >>>> means that everything is reversible, If new microstates are created as the >>>> universe expands, then this expansion cannot be reversed: the creation of >>>> such microstates gives an absolute arrow of time. This is generally >>>> rejected, because physicists tend to believe in unitary dynamics. If >>>> dynamics are not unitary, then the universe is not governed by the >>>> Schrodinger equation, and arguments for the multiverse collapse. >>>> >>> >>> I understand unitarity for a fixed physical system with certain finite >>> boundaries. But how does that work for the case of an expanding universe? >>> If you define the wave function for the observable universe at time 1, what >>> is the wave function for time 2? Doesn't the number of possible states in >>> time 2 not increase beyond what it was in time 1, given new information has >>> entered the system from the cosmological horizon? >>> >> >> If there is a unitary operator that takes the wave function at time 1 to >> time 2, the the evolution is unitary and reversible. Horizons play no part >> in this. >> >>> Also, I think we can borrow a lesson from quantum computing to shed some >>> light on the problem of irreversibility and entropy. Quantum computers need >>> to use reversible logic gates to prevent premature decoherence. Reversible >>> circuits generate garbage (ancilla) bits as a result of the continued >>> operation of the computation. (see >>> https://en.wikipedia.org/wiki/Ancilla_bit and >>> https://quantumcomputing.stackexchange.com/questions/1185/why-is-it-important-to-eliminate-the-garbage-qubits >>> ). >>> >>> If we extend this analogy to the universe, can we envision the rise of >>> complexity/macroscopic order in a similar way to the locally growing order >>> of a reversible computation, which must generate waste heat >>> ("garbage/ancilla bits") leading to global rise in entropy? So long as >>> there are enough places to dump these ancilla bits (such as into the low >>> temperature, non-equalized environment), then there is space for growth of >>> local order through the process of reversible computations. >>> >> >> The quantum process of generating the ancilla bits is unitary, hence >> reversible. If these bits are treated as garbage and thrown away, then the >> result is irreversibility. No new space for bits is created. >> >> > But according to the Bekenstein bound, the maximum possible entropy of a > system is bound by its mass/enegy AND its volume. Two particles by > themselves can encode an infinite amount of information if given infinite > space to place them. > > Wouldn't expanding the available volume for a system increase the number > of bit-combinations you can work with? > The maximum entropy state for a given mass-energy occurs when the entire system forms a black hole. Increasing the volume of space around this BH does not affect the entropy -- it is already at its maximum. The only way to increase this maximum is to increase the amount of mass-energy available -- and simply expanding the universe (available volume) does not do this! Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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