Does time exist in quantum gravity? by Claus Kiefer

Is this a competition or a wedding-party?

Dear Klaus,

I can not see how is clock time related to the directional derivative you define in Eq- 4 and 5. Indeed, you can not forget that time is defined by means of macroscopic clocks, and clocks are not able to define any space derivative.

I believe it is your charge to demonstrate how clock (macroscopic) time is connected to (microscopic) directional derivative. Please clarify this point in order to restore the meaning of the paper.

John

Hi Claus,

You wrote: "Time emerges from the separation into two different subsystems: one subsystem (here: the gravitational part) defines the time with respect to which the other subsystem (here: the non-gravitational part) evolves."[footnote 2]

Footnote 2: "More precisely, some of the gravitational degrees of freedom can also remain quantum, while some of the non-gravitational variables can be macroscopic and enter the definition of time."

May I ask you to elaborate on the GR dictum -- 'matter tells spacetime how to curve and spacetime tells matter where to go' -- in the framework of your ideas, as clarified in footnote 2. Thank you very much in advance.

As to the "problem of time", check out a simple Gedankenexperiment in Wikipedia and its discussion here.

Regards,

Dimi

Dear Professor Kiefer,

While you very convincingly explained your problem with time, thank you, I am worried by your reference to Schroedinger. You gave Ann. Phys. VI 384, 489-527 (1926). Is this correct?

If I recall correctly, I found that Schroedinger wrote the famous equation in his 4th Mitteilung Quantisierung als Eigenwertproblem in Ann. Phys. (1926), not in vol. 384 but already in vol. 81 (4), 109-172.

In order to make sure we refer to the same text, I quote what he wrote below the equation I refer to: "... one may

consider the real part of psi the real wave function, if necessary."

Notice, according to 100 years of Planck's Quantum by Duck and Sudarshan, p. 176, Heisenberg wrote in Z. Phys. 33, 879 (1925): Re{A(n,n-alpha)exp(i omega(n,n-alpha)t}. The authors added a note: The erroneous 'Re' - real part - immediately vanished from Heisenberg's work.

Everybody knows, the also real squared magnitude psi psi* has been preferred instead of the real part. Can you tell me please who introduced this twist from real part to magnitude?

What about your effort to reestablish an arrow of time, do you consider it enough to have a directed time, and do you share Einstein's belief that there is no difference between past and future?

Sincerely,

Eckard Blumschein

Hi Claus,

I very much hope to hear from you. To explain my request posted on Dec. 3, 2008 @ 11:47 GMT, may I quote from your essay (p. 2): The Schrödinger equation (1) is, with respect to t, deterministic and time-reversal invariant. As was already emphasized by Wolfgang Pauli, the presence of both t and i are crucial for the probability interpretation of quantum mechanics, in particular for the conservation of probability in time."

But if we accept your belief that time emerges only as some "semiclassical time", and is (p. 6) "only an approximate concept", how would you address the Hilbert space problem? In your words: "What is the appropriate inner product that encodes the probability interpretation and that is conserved in time?" (C. Kiefer, arXiv:gr-qc/9906100v1, p. 15)

I wonder if you can solve the Hilbert space problem with some "semiclassical time", given your speculation that (Essay, p. 6): "... the Hilbert-space structure, too, is an approximate structure and that different mathematical structures are needed for full quantum gravity."

For if you can't solve the Hilbert space problem, your prerequisites from the Schrödinger equation (p. 2) may not be relevant at all, and you will have to start from scratch, by replacing the Hilbert-space structure with ... well, something else (perhaps "different mathematical structures", as you put it).

I believe Schrödinger provided a viable hint to this 'something else' in November 1950; check out 'Quantum Mechanics 101'.

Regards,

Dimi

Although I like your essay very much -- I think, particularly, that it is very clear and set at almost precisely the level requested -- I am reluctant to vote for it because I cannot see that it has any novelty. A novelty of clear presentation is perhaps worthwhile enough -- indeed sometimes more to be cherished than anything technical -- but is there something in your paper that has a technical novelty that you have not emphasized?

Like many established academics who have submitted essays, you have preferred not to reply to any comments. I would be grateful if you would reply briefly to this. I think your essay could have more fully described in what way it is novel. Academics who specialize in QG will of course know full well in what your essay is novel, but for someone who specializes in QFT it is not obvious.

Godfather or the Engineer's Physics French R. Descartes is 'forgetting Time' in Ballistic Science for at least two reasons:

-Force of a burden on a string is the same two days after than two days before;

-Because Descartes knows too that 'Speed idea' cannot be cutted from Metaphysics and he does not think it is a good idea to put Metaphysics in an essay about Statics.

Contrarily Einstein and Poincaré decided to put Time again (H. Bergson too in Biology fighting against Descartes' method more frankly than Einstein.)

Today fluctuations in Algebraic Geometry between 'block Time' or 'Flow Time' or 'Vector Time', between two dimensions or n-dimensions are coming from this.

Obviously Descartes' Empiricism is too 'dry' for Einstein, Poincaré and Bergson. Their illusion is to think that the trigonometric wave is more fresh than Descartes' arrow although it is just a concave arrow (or a boomerang).

'Block Time' is just an arrangement between the arrow and the flow.

Worm is in the apple from the beginning because Descartes does not understand what some Scientists before him knew (Euclid for instance), i.e. that Time is the Frame of the Algebraic Geometry. Either you forget the Time AND the algebraic Geometry but you cannot split them as he did (and Rovelli on this fq(x)i forum after him).

After Descartes his followers Helmholtz or Beltrami, Riemann are not even aware that there is a difference between Geometry and Algebraic Geometry and that the difference is that there is no Time in Geometry.

Most of Euclid's laws have nothing to do with measurement or geolocalization as Riemann is ignoring it.

And the fight of Bergson, Einstein and Poincaré against Descartes is useless because they share the same paradox, they are catched in the same reference.

The only collision that the LHC experience can involve is the collision between real Physics and algebraic language.

Response from the author

First of all, I would like to thank all persons who

have commented on my essay. In the following I shall briefly try

to respond on some of the questions and comments

in a collective way.

Since I have published in the past various papers on time in

quantum gravity, the question arose what is novel in my essay.

Firstly, the essay is intended to give a concise summary of my thinking

about time in quantum gravity to a broad audience. Secondly, I want

to advocate a novel perspective on the interpretation of the

Wheeler-DeWitt equation and its timeless nature: being very conservative

and imposing only two principles (universal validity of the

Schr"odinger equation and the semiclassical correctness of

Einstein's theory), I argue that there should be a quantum wave equation

behind Einstein's equations and that this wave equation is the

Wheeler-DeWitt equation with all its consequences such as the

absence of a time parameter. This is independent of possible modifications

of the theory at the Planck scale.

I agree that this equation has not been experimentally tested.

However, my claims result from a straightforward and rather mild

extrapolation of theories that *are* empirically established.

It has also been claimed that my essay is "simply a reharsh of the

same ideas as those of Carlo Rovelli ... , Julian Barbour and others ...".

I disagree. Firstly, I have published myself on time in gravity

since 1987. Secondly, there are differences in interpretation.

Whereas for Julian already the classical theory is timeless, for me the

essential feature of timelessness only occurs at the quantum level:

classically, we still have a spacetime at our disposal, which can be

parametrized by time functions in an admittedly non-unique way.

In the quantum theory, on the other hand, spacetime has disappeared

completely as a consequence of the uncertainty relations, and there are

not even the conceptual means available to introduce a classical

time function. Carlo's ideas may be more similar to mine, but

they exhibit a different perspective in formalism: whereas he puts

strong emphasis on operators and the Heisenberg picture, the central

physical quantity for me is the universal wave function.

There are various comments related to the semiclassical approximation.

One question was about the relationship of clock time with the

directional derivative introduced in my essay. The important point here

is that a Schr"odinger equation with its time derivative

(together with the imaginary unit) can be

recovered from the timeless Wheeler-DeWitt equation in an approximate

way. So the point is that standard quantum theory has emerged from

quantum gravity. The relation between clock time and the time parameter

in the Schr"odinger equation is, of course, non-trivial (I could say

more about it), but this is an old problem and not specific to the

main topic of my essay.

I agree with the first comment that the recovery of the imaginary unit

does not disappear in the context of the Dirac equation. Even for

fermionic fields, one has in quantum field theory a functional Schr"odinger

equation. If I say "classical limit", I do not mean a specific choice

of coordinates because, in fact, the (functional) Schr"odinger equation

as recovered from the Wheeler-DeWitt equation is invariant under

coordinate transformations with respect to the (approximate)

background on which it is defined.

As for the Hilbert-space structure, it is only necessary to demand it

to hold at the semiclassical level, that is, at the level where

the Schr"odinger equation holds as an approximate equation.

In my opinion, such a structure is mainly motivated by the presence

of time (so that the total probability is conserved *in* time),

and it is thus unclear whether it survives the disappearance of time.

Depending on the details of the semiclassical approximation,

some of the matter degrees of freedom can appear on the same

footing as gravity, whereas some gravitational degrees of freedom

(e.g. the gravitons) appear even at that level as fully quantum and

have thus to be included into the Hamiltonian of the effective

Schr"odinger equation.

Finally, as for the question about the correct citation of Schr"odinger's

Annalen paper, I want to say the following: one can cite papers

in Annalen der Physik alternatively by an ever-increasing volume number

starting from number 1 in 1799 or you can subdivide it into various

series, with the volume numbering starting from 1 in every new series.

When I quote volume 384, I mean the first choice of referencing.

With the second choice, it would be volume 79 (4th series).

However, I erroneously wrote in my references "Quantisierung als

Eigenwertproblem IV" instead of "II". Maybe it is appropriate to

conclude my response by quoting Schr"odinger himself because this

expresses very much the point of view I adopt in my essay towards

quantum gravity. On page 496 of the quoted paper he writes

(given here in English translation):

"{em We know today, in fact, that our classical mechanics fails for

very small dimensions of the path and for very great curvatures.}

Perhaps this failure is in strict analogy with the failure of

geometrical optics ... that becomes evident as soon as the

obstacles or apertures are no longer great compared with the real,

finite, wavelength. ... Then it becomes a question of searching

for an undulatory mechanics, and the most obvious way is by an

elaboration of the Hamiltonian analogy on the lines of undulatory optics."

Dear DR. Klaus

for time tu understand Einstein and Buddha are needed.

Time exists in quantum gravity when we measure it.

Until time is not measured, time do not exist.

yours amritAttachment #1: Time_Searching_of_Einstein_and_Buddha___Sorli__2009.doc

Dear Claus,

You wrote (Dec. 23, 2008 @ 17:05 GMT) that you "want to advocate a novel perspective on the interpretation of the Wheeler-DeWitt equation and its timeless nature: being very conservative and imposing only two principles (universal validity of the Schr"odinger equation and the semiclassical correctness of Einstein's theory)..."

The first principle you decided to employ, the alleged "universal validity of the Schr"odinger equation", may be wrong, as I tried to argue since I read Ch. 10, 'Quantum gravity and the interpretation of quantum theory', in the first edition of your monograph "Quantum Gravity" (May 2004).

Please check out my essay 'Quantum Mechanics 101'; the link was in my posting from Dec. 11, 2008 @ 14:01 GMT above.

You also wrote (Dec. 23, 2008 @ 17:05 GMT): "In the quantum theory, on the other hand, spacetime has disappeared completely as a consequence of the uncertainty relations, ..."

I believe it is safe to say that, while quantum theory has been empirically established, there could be many *artifacts* from the "filter" we impose on the quantum realm with the 'spacetime of facts' of STR: please check out the KS Theorem in the essay on QM mentioned above.

If you disagree, please explain your arguments.

If you agree, please notice that the Hilbert space problem (C. Kiefer, Quantum geometrodynamics: whence, whither?", arXiv:0812.0295v1 [gr-qc]) may be solved along with the 'problem of time' en bloc , as it should be done.

Looking forward to hearing from you,

Dimi

Time and Quantum of Light. / My opinion./

Can Time Exist Without Matter?

1.

According to Newton the answer is " Yes".

2.

According to SRT and GRT the answer is " No".

3.

Who is right? Who is wrong?

What is the resolution of this apparent paradox?

===========================..

There are two kinds of time:

a) the proper (individual) time and

b) the planetary time.

They are so familiar that we rarely give them thought.

Don't we know, that time for living being is limited

and the planetary time is absolute for them ? It is.

Maybe therefore Newton declared that time is absolute.

It " flows equably without relation to anything external"

he wrote in 1687. But Einstein had another opinion.

He wanted to know: " Where does the conception of time

come from?", " What is the essence of time?".

And to explain these questions he created two theories:

SRT and GRT and declared that time is relative, changeable.

1.

SRT explains behavior and the proper time of light

quanta /electron. Why do I think so?

a)

One law (postulate) of SRT says that speed of light quanta

is constant c=1. Second law ( postulate ) says no another particle

can reach this speed. So there are two incommensurable

quantities. Is it possible to bind them together? No. I was

taught at school from the first class that the incommensurable

quantities cannot be compared. The connection between these

incommensurable quantities is similar to the decision of a

problem: "What will be if the whale attacks the elephant?"

We can see whale in a ocean and elephant in a savanna,

but they never meet and fight in the same " frame of reference".

And the same is about light quanta and another particles.

We cannot see them together in SRT. We can meet only the

light quanta in SRT and no other particles in it.

b)

SRT was born from Maxwell's theory and it is a continuation

of the electrodynamics' development . The electron is a main

and single hero in the Maxwell's theory and SRT. There

isn't the Maxwell's theory / SRT without electron.

It is not correct to compare electron/ light quanta with another

particles (protons...etc) and bodies (billiard balls, satellites,

astronauts, "twins") because they cannot produce electromagnetic

fields. The electron and the another particles are also incommensurable

quantities. They are absolutely different objects.

c)

Every epoch has its own delusion. Maxwell and Boltzmann

tried to explain electromagnetic fields using balls, wheels,

cog-wheels, springs...etc. H. Hertz, who demonstrated the

existence of the electromagnetic waves, wrote that the

electromagnetic waves didn't have practice use. Etc....

Now we try to compare electron/photon

ability with astronaut's and "twins' " opportunities.

It is mistaken, but what to do? We do it because this is

our way of cognition:

" From vague wish to the bright thought".

2.

So, how SRT explains time from electron/ light quanta point of view.

a)

When light quanta is in state of a rest its time is frozen,

and its own clock shows zero.

b)

When photon moves with constant speed c=1

its time is also frozen, and its own clock still shows zero.

c)

Only when photon moves with speed c>1 its zero time

changes and limited time appears. In this situation we

know photon as an electron. Photon works as an electron

and SRT and Lorentz transformations explain this process.

d)

And when , for example, electron emits from an atom and

interacts with Vacuum all its parameters change. Its limited

time ends and its own clock shows zero again. Now it lives

in infinite/ eternal Vacuum until new incarnation, until its new

work, maybe, in an atom (molecule), or in a cell, maybe, in a blade

of grass or in a tree, maybe, in an animal or in a person.

In another words:" We are living beings until Light quanta/

Electron is present and works in our body."

Is it true? Yes, it is true. Why?

Because W. Pauli in 1924 wrote:" Each quantum state in the atom

is not limited of two electrons, but only one electron".

It means in the atom can be only one, single electron.

The electron manages the atom. If the atom contains more

than one electron (for example - two), this atom represents

" Siamese twins". Save us God of having such atoms and cells.

And the living being begins its life from one, singe cell.

What I am introducing here is what ' thinking photon/ electron' exist .

I applied the quantum of light/ photon/ electron with a consciousness.

And His own consciousness is not static but can develop.

The development of conscious scale goes

" from vague wishes up to a clear thought ".

This evolution proceeds during hundred millions (billion) years.

e)

Trying to understand " the electrodynamics of moving bodies"

Einstein wrote that it is the result of time and space changes.

It is not exactly correct , because these changes are secondary

in SRT. And the first point of SRT is that Quantum of light changes

its spin. The former Planck/ Einstein's spin (h) changes in Goudsmit /

Uhlenbeck's spin (h = h / 2pi), and as a result of this act all its parameters

change and the time and new space appear.

3.

GRT explains the conditions of gravitation and the secret of

planetary time. Why do I think so?

a)

When Einstein worked on GRT, he asked astronomers:

" What is the average mass of matter in the Universe?"

The result was lamentable. The quantity of mass was

insignificantly small. It was impossible to keep gravitation

law with such insignificantly little mass and so, the Universe

must be "open", endless. But what to do with the infinite

space, Einstein didn't know. Therefore he took (from the

heaven) " the cosmological constant" in order to "close"

the Universe. The taken mass was enough for creating the

condition of gravitation. Without " the cosmological constant"

the Universe is endless.

b)

In 1922 Friedman wrote, that we could not take " the

cosmological constant" in calculation. Instead of it, it is

enough to take "time" and the Universe will be "closed".

Friedman was correct, but why? Because "time", by its

nature, is a limited physical quantity and, be taken in

mathematical calculation, automatically gives "closed" result.

c)

So, the detected material mass of the

matter in the Universe is so small (the average density

of all substance in the Universe is approximately

p=10^-30 g/sm^3) that the gravitation law doesn't work.

Astronomers and astrophysicists know about this fact and

therefore (to save the gravitation law) invented new matter

a "dark matter", a new energy a "dark energy" and another

abstract objects. This " invention" is only a result of our

mentality , which says: " If in a theory you meet infinity it

means the theory is nonsense". It is very hard to take that

the Universe is infinite. It is no easy matter to give up

a lifetime of habit .

d)

On my opinion it is impossible to use GRT to Universe as

a whole. The Newton/ Einstein's gravitation laws are correct

only in the local parts of Vacuum. The Universe / Vacuum

as a whole is endless.

e)

So, how does GRT explain time?

According to GRT the time depends on the mass

and speed it means, of moving matter.

It means that different masses and speeds can create

different time. For example, our planet Earth has its

own time but for us it is absolute.

The other planets have another mass and speed and

therefore they have their own time. This time according

to GRT is relative. But their habitants will think that their

time is absolute. But if they know GRT they will

not make this mistake.

=============

According to SRT and GRT time is relative.

SRT says about proper/ individual time of an

electron/ light quanta.

GRT says about planetary time of a Planet..

The time cannot exist without matter and speed,

in another words, without moving matter. But

different reasons and different moving of a matter

create the proper and planetary time.

=================..

Is it possible to see the different manifestation of

time in a human being?

Here is an article " Even the time is pressed from fear"

by Dr. Vadim Chernobrov (collaborator of MAI -

- Moscow Aviation Institute).

He wrote, that we usually think time is a constant quality.

But Einstein's relative theory says time is relative.

Question. Is it possible to check it in our life?

Answer. Russian and foreign researches say it is

possible. The documents (secret in the past) testify

that "cataclysm of time", " phenomenon of time's

perversion "," the changes (its deceleration) of time"

often is observed by people whose profession connected

with risk: astronauts, pilots, drivers, soldiers.

1.

The test pilot Mark Gallay wrote in his book

"The test in the sky" when his airplane was caught

with fire " the time began to go in another scale. The time

almost stopped. Every second took ability of expansion,

and in this situation it was possible to do many things."

He confirms that tested such feeling many times.

2.

The test pilot Marina L. Popovich said the same,

in the dangerous, catastrophic situations " the time

is stretches".

3.

In June 1989 the soviet airplane MIG-29 crashed near

Paris, in Le Bourget airport , in the time of its air show.

The notes of "the black box" showed that during the

four (4)seconds the test pilot Anatoly Kvochur made as

many operations as in normal situation it would take some

minutes. The test pilot later said: " the time was stretched".

4.

The captain N.Z.(fought in Afghanistan) remembers:

"the fly of the bullet was so beautiful that I didn't guess

to evade from it, although I have enough time to do it".

5.

The sergeant V. Ch (fought in Afghanistan) told:

" The black barrel of gun seems very big, even enormous.

Time is stopped and full silence came. And I moved slowly

a step a side and the bullet passed close to me."

6.

Etc...

His conclusions.

The people in a critical situation, on the border of death,

suddenly for themselves begin to see everything as in the

slow down film and in this time their speed reaction and

power increase in tens and hundreds times. And this explains:

a) why a man who escaped from wolves, can quickly reach

up the top of the naked tree,

b) an old woman took out a big trunk from her burned house,

which later two strong firemen couldn't rise.

c) etc...

=============..

My experience.

The speed on the curve was so fast that to keep the balance of

the car I went on other road line and flew straight at the

"forehead' of a green mercedes. The driver of the mercedes

was in panic, in horror. He threw the wheel and closed his face

with his hands. Suddenly the time stopped and the sound disappeared

for me and I made many actions before my car kicked only the side

back door of the mercedes. It was long time ago, but writing this article

I understood better what happened.

Our computer-brain works on a dualistic basis (on two different neurons

systems): 1) usually under logic program,

2) sometimes on intuition (subconscious).

Brain of a man approximately consists of sixteen milliards neurons.

All of them form the system that manages human body.

That is why that with the work of all the sixteen milliards neurons

of brain, a man cannot catch a single impulse of his Electron, of his

Quantum of light, of his Soul:

(mass of electron is equal 10^-31 kg., charge of electron is equal 10^-19 k.)

But in that time ( critical time ) most neurons of my brain stopped

their electric pulse (time almost stopped) and my Light Quanta/Electron

in this new condition (superconductivity) had possibility to increase

my speed reaction and power on a short period of time . So, as SRT says,

the Light Quanta in different systems ( even in our brain) can show us

a different Time. The Light Quanta plays major role in the Nature,

in the Physics, in our Life.

==========.

Best wishes.

Israel Sadovnik. Socratus.Attachment #1: 450pxSocrates_Louvre.jpg

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