# 權力來源 1.4

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~ environmental default

— Me@2021-11-16 07:59:12 PM

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~ potential

~ 未來事件s對現在的影響

— Me@2023-03-12 09:14:50 AM

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potential energy

~ energy of potential motion

~ energy of future motion

— Me@2023-04-16 12:08:08 PM

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~ 勢力

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「權力」著重個人，例如：「甲擁有很大的權力。」「勢」則著重外在。甲身處環境的人事心理結構，形成了一個「勢」。如果當時的那個「勢」對甲有利，就簡稱為：「甲擁有很大的勢力。」

— Me@2023-04-17 12:56:11 AM

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# Debugging quantum concepts

Reality is a superposition of eigenstates. Even if we use the pilot-wave formalism, in which a particle has definite position or momentum, the pilot wave itself is in a superposition.

— Me@2012-04-16 2:27:20 PM

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Physics reality is NOT a superposition of eigenstates. If physics reality was a superposition of eigenstates, there would have never been any interference patterns.

For an experimental setup, what is in a superposition is the quantum state, which is a tool for deducing probabilities of different potential measurement results.

“A quantum state is a superposition of eigenstates” just means nothing more than that we need to use individual probabilities of the eigenstates to calculate the probabilities.

A quantum state, which is represented by a wave function, is logical, mathematical, conceptual, and linguistic in nature. A quantum state is NOT physical. A quantum state is NOT reality. A quantum state is NOT directly corresponding to a physical reality (aka observable events, measurement results, etc.)

A quantum state is NOT even corresponding to a probability directly. (If a quantum state was a probability, there would have never been the phenomenon of interference.) Instead, a quantum state is corresponding to a probability amplitude, which is used for calculating probabilities.

— Me@2023-03-16 09:57:07 AM

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# Intermediate states

What happens in the interval between the initial and final states of the interaction process?

What happens in between is everything and nothing. There is no privileged clearcut answer what happened that would be physically meaningful. It’s really the very basic point of quantum mechanics that only results of measurements are physically meaningful facts or observables; all other data are fictitious or uncertain. By the very definition of your problem, no measurement took place in the intermediate states which means that no sharp answers to any questions were generated, no answers or values became real or privileged or facts.

But unlike classical physics, quantum mechanics says that not only the probabilities of each history matter. All the relative phases matter, too.

— answered Jan 9, 2021 at 16:10

— Luboš Motl

— Physics StackExchange

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2023.03.02 Thursday ACHK

# Looper, 6

Causal diamonds in time travel, 3

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Time travel in the absolute sense is logically impossible.

If time travel was logically possible, it still could be logically consistent from the time traveller’s point of view, as long as he cannot see from the perspective of the meta time.

— Me@2016-06-01 07:10:51 AM

— Me@2023-02-23 12:13:20 PM

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# Causal diamonds in time travel, 2

Time travel in the absolute sense is logically impossible.

If time travel was logically possible, no observer would see any paradox if there is no meta-observer, who can compare results seen by different observers.

— Me@2016-06-12 12:12:40 PM

— Me@2023-02-13 12:53:31 AM

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# MSI RTX 3060 Ti VENTUS 2X 8G OCV1 LHR

Visualizing higher dimensions, 2.2 | Remove time from physics, 2

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Mathematics is local (left brain).

Physics is global (right brain).

— Me@2017-06-22 06:16:59 PM

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Mathematical processes, i.e. the calculations, are local.

Physical intuitions before a calculation and the interpretations after are global.

— Me@2023-01-13 07:45:24 PM

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However, in an opposite sense, physics is local and mathematics is global.

— Me@2023-01-14 08:13:17 PM

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Geometry is global.

Space is what we can see at once.

Dynamics is local.

Time is what we cannot see at once.

— Me@2017-02-07 10:11:34 PM

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… math is what you get when you remove time from physics.

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# Black hole mass can’t be

A singularity doesn’t have mass. Mass is a property of an object that exists in time. A (spacelike, e.g. Schwarzschild) singularity is not an object that exists in time. A singularity is a moment in time when time ends along with mass. Furthermore, a black hole does not have a center. The geometry of the Schwarzschild spacetime inside the horizon is an infinitely long 3-cylinder with a quickly shrinking circumference. Also, no black hole solution is valid inside the horizon, because all solutions assume a static metric, but it is not static inside the horizon.

— safesphere

— May 20, 2019 at 10:38

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And if you wanted to say that the whole mass $M$ is obtained from the singularity, you won’t be able to get a good calculation because the integral over the singularity would be singular. Moreover, the space and time are really interchanged inside the black hole (the signs of the components $grr$ and $gtt$ get inverted for $r < 2GM$) so the exercise is in no way equivalent to a simple 3D volume integral of $M \delta(x) \delta(y) \delta(z)$. The Schwarzschild singularity, to pick the "simplest" black hole, is a moment in time, not a place in space. It is the final moment of life for the infalling observers. In a locally (conformally) Minkowski patch near the singularity with some causally Minkowskian coordinates $t,x,y,z$ and $r = |(x,y,z)|$, the Schwarzschild singularity looks like a $t=t_f$ hypersurface, not as $r=0$.

— Black hole mass can't be visualized as a property of the black hole interior

— Lubos Motl

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2022.11.08 Tuesday ACHK

# Coherent light source

superkuh 17 hours ago [–]

Coherence isn’t what you think it is. It is not an “alignment in phase” of the sinusoid, like all the lay diagrams show. It isn’t even being the same frequency. In the early days of quantum physics the light sources were mercury arc lamps (muliple freqs) that achieved coherence by shining through tiny pinholes.

https://web.archive.org/web/20220820182938/http://amasci.com/miscon/coherenc.html

Coherence is being a point source. Stars, except for our sun since it is too close, are coherent light sources.

— Hacker News

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2022.10.27 Thursday ACHK

# Swampland

In physics, the term swampland refers to effective low-energy physical theories which are not compatible with string theory, in contrast to the so-called “string theory landscape” of compatible theories. In other words, the swampland is the set of consistent-looking theories with no consistent ultraviolet completion in string theory.

Developments in string theory suggest that the string theory landscape of false vacua is vast, so it is natural to ask if the landscape is as vast as allowed by consistent-looking effective field theories. Some authors, such as Cumrun Vafa, suggest that is not the case and that the swampland is in fact much larger than the string theory landscape.

— Wikipedia on Swampland (physics)

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Recall that Vafa’s Swampland is a giant parameter space of effective field theories that cannot be realized within a consistent theory of quantum gravity i.e. within string/M-theory. Only a tiny island inside this Swampland, namely the stringy Landscape, is compatible with quantum gravity. String/M-theory makes lots of very strong predictions – namely that we don’t live in the Swampland. We have to live in the special hospitable Landscape.

— Vafa, quintessence vs Gross, Silverstein

— The Reference Frame

— Luboš Motl

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2022.10.21 Friday ACHK

# For all, 10

No observer can observe and get all the information of the current state of the whole universe.

Since the definition of the “universe” is “everything”, any observer must be part of the universe. Also, in the universe, any observer has at least one thing it cannot observe directly—itself.

Therefore, no observer can observe the whole universe in all details.

— Me@2022.09.30 07:57:46 PM

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Can a part of a painting represent all the information of the whole?

No.

(Kn: Yes, if excluding itself.)

That is exactly my point.

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“Yes only if that part does not contain that part itself” is equivalent to “no”.

— Me@2016-08-20 03:30:26 PM

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# Photons in expanding space

If a photon (wave package) redshifts (stretches) travelling in our expanding universe, is its energy reduced?

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Since you say you’re talking about what happens locally (in a small volume), I’ll answer from that point of view. The usual formulation of energy conservation in such a volume is that energy is conserved in an inertial reference frame. In general relativity, there are no truly inertial frames, but in a sufficiently small volume, there are reference frames that are approximately inertial to any desired level of precision. If you restrict your attention to such a frame, there is no cosmological redshift. The photon’s energy when it enters one side of the frame is the same as the energy when it exits the other side. So there’s no problem with energy conservation.

The (apparent) failure of energy conservation arises only when you consider volumes that are too large to be encompassed by a single inertial reference frame.

To be slightly more precise, in some small volume $V=L^3$ of a generic expanding Universe, imagine constructing the best possible approximation to an inertial reference frame. In that frame, observers near one edge will be moving with respect to observers near the other edge, at a speed given by Hubble’s Law (to leading order in $L$). That is, in such a frame, the observed redshift is an ordinary Doppler shift, which causes no problems with energy conservation.

If you want more detail, David Hogg and I wrote about this at considerable (perhaps even excessive!) length in an AJP paper.

— Photons in expanding space: how is energy conserved?

— answered Aug 16, 2011 at 15:31

— Ted Bunn

— Physics Stack Exchange

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2022.09.11 Sunday ACHK

# Quantum as potential, 2

Only measurement results (aka physical phenomena) form the physical reality.

Quantum Mechanics is a theory of measurement results.

Quantum Mechanics is a theory of reality.

Quantum Mechanics is not a theory of unobservables (undefined-observables).

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Quantum mechanics is a story of reality, not a story of story.

— Me@2022-07-27 10:38:32 AM

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# Quantum as potential

Realist view is wrong.

Before measurement, there are quantum potentials only.

quantum ~ potential

Note that it is NOT the “quantum potential” in the Bohm interpretation.

— Me@2016-08-21 06:13:49 PM

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A wave function encodes the probabilities of different potential measurement results of a physical experiment. It is not a physical wave.

Quantum superposition is NOT a superposition of realities.

Physics should consider only measurement results and their probabilities. Only measurement results are realities.

No measurement result, aka physical phenomenon, is in a superposition.

For example, in the double-slit experiment, the measurement results are (the locations of) the dots on the final screen. Every dot location is not in a superposition.

— Me@2022-07-25 06:43:05 PM

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# Schrodinger’s cat, 3.5

This description is wrong.

Quantum superposition is exhibited in fact in many directly observable phenomena, such as interference peaks from an electron wave in a double-slit experiment.

— Wikipedia on Quantum superposition

Whatever you observe, it is not a superposition.

If no left-right detector is allowed, the moving-left/right variable is an unobservable. What you observe, instead, is the dot on the final screen.

In other words, the observable is the final position of a particle when it reaches the final screen. And the final screen itself acts as the detector for that observable.

Superposition is unobservable due to the lack of definition (of the distinction between different states) of the corresponding physical variable, due to the fact that no corresponding detector, such as the left-right detector, is allowed in the experimental design.

physical phenomena

~ observable events

Superposition

~ logically unobservable, since not yet defined

~ not yet defined, since logically undefinable

~ logically undefinable, since no corresponding detector is allowed

A superposition state is not an observable state. In other words, it is not a physical state. Then what is the point of considering it?

Although a superposition state is not a physical state, it is a mathematical state that can be used to calculate the probabilities of different possible physical-states/observable-events.

— Me@2022-07-06 06:00:55 PM

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# Schrodinger’s cat, 3.4

A macroscopic system (such as a cat) may evolve over time into a superposition of classically distinct quantum states (such as “alive” and “dead”).

— Wikipedia on Quantum superposition

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The components of a superposition must be indistinguishable states.

A superposition is neither an AND state nor an OR state.

AND or OR are only possible for more than one state.

AND or OR are only possible for at least 2 (distinguishable) states.

The cat is not in a superposition state of “alive” and “dead”.

A mixed state is an OR state (of at least 2 distinguishable states).

— Me@2022-07-03 11:02:24 AM

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# Schrodinger’s cat, 3.3

The modern view is that this mystery is explained by quantum decoherence.

Quantum decoherence is useful, but NOT necessary.

It is useful for the self-consistency checking of quantum mechanics.

Some microscopic states are expressed as (mathematical) superpositions of macroscopic-indistinguishable-if-no-measuring-device-is-allowed states.

Two states are called “macroscopic-distinguishable” only if they result in two different physical phenomena. In other words, the distinction must be observable.

an eigenstate

~ an observable (at least in principle) state

~ a physical state

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a superposition state

~ an unobservable (even in principle) state

~ a mathematical (but not physical) state

We define microscopic states and events in terms of macroscopic states and events. A consistent theory must be able to deduce (explain or predict) macroscopic states and events from those microscopic states and events.

— Me@2022-06-15 07:40:37 PM

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# Eigenstates 3

an eigenstate

~ an state identical to the overall average

In analogy, in the equation

$\displaystyle{\frac{12+13+14}{3}=13}$,

the number 13 appears both on the left (as one of the component numbers) and on the right (as the overall average).

In this sense, the number 13 is an “eigenstate”.

— Me@2016-08-25 01:36 AM

— Me@2022-06-28 08:19 PM

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An eigenstate has a macroscopic equivalence.

— Me@2016-08-29 06:10:21 PM

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An eigenstate is a microstate that has a corresponding macrostate.

An eigenstate is a mathematical state which is also a physical state.

An eigenstate is an observable state.

— Me@2022-06-28 07:36:40 PM

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# Schrodinger cat’s misunderstanding

Schrodinger’s cat, 3.2

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In 1935, Erwin Schrödinger devised a well-known thought experiment, now known as Schrödinger’s cat, which highlighted this dissonance between quantum mechanics and classical physics.

The main point of the Schrödinger’s cat thought experiment is NOT to prove that there should also be superposition for macroscopic objects. Instead, the main point of the thought experiment is exactly the opposite—to prove that regarding a superposition state as a physical state leads to logical contradiction.

— Me@2022-06-15 07:19:36 PM

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# Schrodinger’s cat, 3.1

It is natural to ask why ordinary everyday objects and events do not seem to display quantum mechanical features such as superposition. Indeed, this is sometimes regarded as “mysterious”, for instance by Richard Feynman. In 1935, Erwin Schrödinger devised a well-known thought experiment, now known as Schrödinger’s cat, which highlighted this dissonance between quantum mechanics and classical physics.

The modern view is that this mystery is explained by quantum decoherence. A macroscopic system (such as a cat) may evolve over time into a superposition of classically distinct quantum states (such as “alive” and “dead”). However, the state of the cat is entangled with the state of its environment (for instance, the molecules in the atmosphere surrounding it). If one averages over the quantum states of the environment—a physically reasonable procedure unless the quantum state of all the particles making up the environment can be controlled or measured precisely—the resulting mixed quantum state for the cat is very close to a classical probabilistic state where the cat has some definite probability to be dead or alive, just as a classical observer would expect in this situation.

Quantum superposition is exhibited in fact in many directly observable phenomena, such as interference peaks from an electron wave in a double-slit experiment. Superposition persists at all scales, provided that coherence is shielded from disruption by intermittent external factors. The Heisenberg uncertainty principle states that for any given instant of time, the position and velocity of an electron or other subatomic particle cannot both be exactly determined. A state where one of them has a definite value corresponds to a superposition of many states for the other.

— Wikipedia on Quantum superposition

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It is natural to ask why ordinary everyday objects and events do not seem to display quantum mechanical features such as superposition. Indeed, this is sometimes regarded as “mysterious”, for instance by Richard Feynman.

Superposition is not “mysterious”. It is “mysterious” only if you regard “a superposition state” as a physical state.

Only observable states are physical states. Any observable, microscopic or macroscopic, is NOT a superposition.

A superposition is NOT observable, even in principle; because the component states of a superposition are physically-indistinguishable mathematical states, aka macroscopically-indistinguishable microscopic states.

(Those component states, aka eigenstates, are observable and distinguishable once the corresponding measuring device is allowed.)

They are indistinguishable because the distinction is not defined in terms of the difference between different potential experimental or observational results.

Actually, the distinction is not even definable, because the corresponding measuring device is not allowed in the experimental design yet.

— Me@2022-06-15 11:51:22 AM

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