If you are aware of an interesting new academic paper (that has been published in a peer-reviewed journal or has appeared on the arXiv), a conference talk (at an official professional scientific meeting), an external blog post (by a professional scientist) or a news item (in the mainstream news media), which you think might make an interesting topic for an FQXi blog post, then please contact us at forums@fqxi.org with a link to the original source and a sentence about why you think that the work is worthy of discussion. Please note that we receive many such suggestions and while we endeavour to respond to them, we may not be able to reply to all suggestions.

Please also note that we do not accept unsolicited posts and we cannot review, or open new threads for, unsolicited articles or papers. Requests to review or post such materials will not be answered. If you have your own novel physics theory or model, which you would like to post for further discussion among then FQXi community, then please add them directly to the "Alternative Models of Reality" thread, or to the "Alternative Models of Cosmology" thread. Thank you.

Please also note that we do not accept unsolicited posts and we cannot review, or open new threads for, unsolicited articles or papers. Requests to review or post such materials will not be answered. If you have your own novel physics theory or model, which you would like to post for further discussion among then FQXi community, then please add them directly to the "Alternative Models of Reality" thread, or to the "Alternative Models of Cosmology" thread. Thank you.

Forum Home

Introduction

Terms of Use

By using the FQXi Forum, you acknowledge reading and agree to abide
by the Terms of Use

RSS feed | RSS help

Introduction

Terms of Use

*Order posts by:*

*Display:*

RSS feed | RSS help

RECENT POSTS IN THIS TOPIC

**smith machinist**: *on* 4/13/19 at 8:05am UTC, wrote norton.com/setup -- Activating The Norton Antivirus If You Already Have...

**GAURAV KUMAR**: *on* 2/2/19 at 9:36am UTC, wrote mcafee activate | mcafee.com/activate | mcafee/activate McAfee providing...

**Sandra Rose**: *on* 1/24/19 at 10:40am UTC, wrote wexred

**spin offevent**: *on* 1/24/19 at 6:46am UTC, wrote The spinoff is the most trending Corporate event agency in Gurgaon in 2019....

**Mercy James**: *on* 10/10/18 at 11:58am UTC, wrote Give a chance to express views thanks for it. vmware coupons have been a...

**ariana pham**: *on* 8/11/18 at 1:55am UTC, wrote Nice to read the information here. The content of this post is very useful...

**john adward**: *on* 7/24/18 at 6:49am UTC, wrote McAfee protects all your devices from online threats like virus attacks,...

**john adward**: *on* 7/24/18 at 6:47am UTC, wrote McAfee protects all your devices from online threats like virus attacks,...

FQXi FORUM

April 20, 2019

Natalie Wolchover has a fascinating interview with string theorist Ed Witten, in Quanta on dualities and what is real and fundamental. Thank you to Steve Agnew for suggesting that this would be a could discussion topic.

report post as inappropriate

report post as inappropriate

Edward Witten: "I tend to assume that space-time and everything in it are in some sense emergent. By the way, you'll certainly find that that's what Wheeler expected in his essay. As you'll read, he thought the continuum was wrong in both physics and math. He did not think one's microscopic description of space-time should use a continuum of any kind - neither a continuum of space nor a continuum of time, nor even a continuum of real numbers. On the space and time, I'm sympathetic to that."

One of my comments in Quanta:

"Emergent space-time" is a category mistake. Specetime has already emerged - it is a deductive consequence of Einstein's constant-speed-of-light postulate:

"Special relativity is based on the observation that the speed of light is always the same, independently of who measures it, or how fast the source of the light is moving with respect to the observer. Einstein demonstrated that as an immediate consequence, space and time can no longer be independent, but should rather be considered a new joint entity called "spacetime."

Anything deduced from different premises would fall in a different category and would have nothing to do with Einstein's spacetime - combining the two concepts would be absurd. For instance, bringing granularity to spacetime is equivalent to painting spacetime in yellow. If the original concept of spacetime is unacceptable and should be replaced, then the underlying premise, Einstein's constant-speed-of-light postulate, is false and should be abandoned. The step is unavoidable if logic is obeyed.

Pentcho Valev

report post as inappropriate

report post as inappropriate

One of my comments in Quanta:

"Emergent space-time" is a category mistake. Specetime has already emerged - it is a deductive consequence of Einstein's constant-speed-of-light postulate:

"Special relativity is based on the observation that the speed of light is always the same, independently of who measures it, or how fast the source of the light is moving with respect to the observer. Einstein demonstrated that as an immediate consequence, space and time can no longer be independent, but should rather be considered a new joint entity called "spacetime."

Anything deduced from different premises would fall in a different category and would have nothing to do with Einstein's spacetime - combining the two concepts would be absurd. For instance, bringing granularity to spacetime is equivalent to painting spacetime in yellow. If the original concept of spacetime is unacceptable and should be replaced, then the underlying premise, Einstein's constant-speed-of-light postulate, is false and should be abandoned. The step is unavoidable if logic is obeyed.

Pentcho Valev

report post as inappropriate

Nima Arkani-Hamed (06:09): "Almost all of us believe that space-time doesn't really exist, space-time is doomed and has to be replaced by some more primitive building blocks."

Any substitute for spacetime that emerges from "some more primitive building blocks", that is, is deduced from premises different from the principle of relativity and the constancy of the speed of light, has nothing to do with Einstein's spacetime. The two fall in different categories. The new "spacetime" could replace the old one, but then the rejection of Einstein's spacetime would entail that at least one of Einstein's 1905 postulates is false.

Marcelo Gleiser: "The challenge is to somehow bring the notion of granularity to spacetime, bring the discrete to the continuous. This is the problem that has baffled theoretical physicists for at least half a century."

This is insane. Spacetime is not an ab initio model that one can modify, e.g. by introducing granularity. It is a DEDUCTIVE CONSEQUENCE of Einstein's constant-speed-of-light postulate, and if the consequence is unacceptable, the postulate is false (logic forbids the combination "true postulate, unacceptable consequence"). In other words, you cannot "retire" Einstein's spacetime without declaring the postulate false:

What scientific idea is ready for retirement? Steve Giddings: "Spacetime. Physics has always been regarded as playing out on an underlying stage of space and time. Special relativity joined these into spacetime... [...] The apparent need to retire classical spacetime as a fundamental concept is profound..."

Pentcho Valev

report post as inappropriate

Any substitute for spacetime that emerges from "some more primitive building blocks", that is, is deduced from premises different from the principle of relativity and the constancy of the speed of light, has nothing to do with Einstein's spacetime. The two fall in different categories. The new "spacetime" could replace the old one, but then the rejection of Einstein's spacetime would entail that at least one of Einstein's 1905 postulates is false.

Marcelo Gleiser: "The challenge is to somehow bring the notion of granularity to spacetime, bring the discrete to the continuous. This is the problem that has baffled theoretical physicists for at least half a century."

This is insane. Spacetime is not an ab initio model that one can modify, e.g. by introducing granularity. It is a DEDUCTIVE CONSEQUENCE of Einstein's constant-speed-of-light postulate, and if the consequence is unacceptable, the postulate is false (logic forbids the combination "true postulate, unacceptable consequence"). In other words, you cannot "retire" Einstein's spacetime without declaring the postulate false:

What scientific idea is ready for retirement? Steve Giddings: "Spacetime. Physics has always been regarded as playing out on an underlying stage of space and time. Special relativity joined these into spacetime... [...] The apparent need to retire classical spacetime as a fundamental concept is profound..."

Pentcho Valev

report post as inappropriate

All due respects for Ed Witten, but quantum communications are looking very realistic today. And it's the Chineese whom are taking the lead, at least publicly, with the first of a planned 20 satellites. It takes no great leap of understanding to recognize that an instantaneous correlation of paired events making communications undetectable in the first place, let alone decipherable, would render...

view entire post

view entire post

report post as inappropriate

John,

Your comment about "making communications undetectable in the first place, let alone decipherable" is not quite correct. The communications are potentially both detectable and decipherable. But they are non-compromisable, since, for example, it is possible to determine that someone has attempted to intercept a distributed key. In effect, an adversary can jam the system by constantly attempting to intercept such a system. Thus, while one might know when the system is in a secure state, that state can be denied by a suitable denial-of-service attack. Denying an adversary their secure form of communications, in order to force them to use an insecure one, whenever it is essential for them to communicate, is a common strategy in communications warfare.

Rob McEachern

report post as inappropriate

Your comment about "making communications undetectable in the first place, let alone decipherable" is not quite correct. The communications are potentially both detectable and decipherable. But they are non-compromisable, since, for example, it is possible to determine that someone has attempted to intercept a distributed key. In effect, an adversary can jam the system by constantly attempting to intercept such a system. Thus, while one might know when the system is in a secure state, that state can be denied by a suitable denial-of-service attack. Denying an adversary their secure form of communications, in order to force them to use an insecure one, whenever it is essential for them to communicate, is a common strategy in communications warfare.

Rob McEachern

report post as inappropriate

It is all a question of numbers after all...if a continuum is composed of 1e39 bits per angstrom, why is that different from a continuum?

Einstein's spacetime is a continuum approximation of a very large number of discrete quanta. So spacetime works very well and quantum works very well and all we need is a connection that also works very well...

report post as inappropriate

Einstein's spacetime is a continuum approximation of a very large number of discrete quanta. So spacetime works very well and quantum works very well and all we need is a connection that also works very well...

report post as inappropriate

The space-time continuum has issues. What is seen in a reference frame has to be a sensory product or product of a device, post receipt and processing of EM signals. Vision requires that causal order of EM signal receipt preceding product seen. The process from detection of signal to product generation gives a resolution to the product so that it is not a continuum. Whether because of the limited number of cells of the visual cortex or pixels display-able on a screen.

report post as inappropriate

report post as inappropriate

Quote: "I tend to assume that space-time and everything in it are in some sense emergent." Edward Witten. Yes, it has to be because Einstein was referring to what is *seen*. Being a physicist and not a biologist the process of seeing was not built into the work.

report post as inappropriate

report post as inappropriate

As discreet sensors of some kind or another have to collect the em signals prior to their processing, discreetness is input to the production of seen space-time products. Even though some aggregation and averaging of the information generated from the signals occurs it isn't amalgamated into a fully continuous whole. The information is carried by discreet neurons or circuits. The information that ends up as the product is confined to the discreet components of the host surface.

report post as inappropriate

report post as inappropriate

Hello everyone,

Needed some help please with a question.

Suppose we have an equation f(t) which is a function showing the displacement of a particle at a different point in time.

How do I try to model this equation into a quantum oscillator, like Schrodinger?

Thanks!

Ajay Pokharel

report post as inappropriate

Needed some help please with a question.

Suppose we have an equation f(t) which is a function showing the displacement of a particle at a different point in time.

How do I try to model this equation into a quantum oscillator, like Schrodinger?

Thanks!

Ajay Pokharel

report post as inappropriate

Ajay,

I was just looking in and gave your equation a quick eyeball. I see the general form and you might have something there, if you think of the particle 'skipping over the ocean like a stone'. Or at least one displacement to a different point in time. It would be the same thing as a particle shedding its relativistic mass more rapidly than it can shed its velocity, and the two continuous functions converging to a point of different time of the space. jrc

report post as inappropriate

I was just looking in and gave your equation a quick eyeball. I see the general form and you might have something there, if you think of the particle 'skipping over the ocean like a stone'. Or at least one displacement to a different point in time. It would be the same thing as a particle shedding its relativistic mass more rapidly than it can shed its velocity, and the two continuous functions converging to a point of different time of the space. jrc

report post as inappropriate

Sorry for elementary question. Trying to understand quantum theory. Basic stuff. When detecting individual photons in double slit experiment, does each photon detected have the same intensity/energy or does intensity vary across interference pattern. Ie, is interference pattern caused by more and fewer photons or by photons with lower intensity? I assume all wavelengths are the same.

Same question when detecting interference pattern of electrons.

Realize this may be wrong place to ask this question. Proper link to do so would be appreciated. Thanks.

report post as inappropriate

Same question when detecting interference pattern of electrons.

Realize this may be wrong place to ask this question. Proper link to do so would be appreciated. Thanks.

report post as inappropriate

Dear FQXi.org Members,

Reality am fundamental. Reality am not theoretical.

My research has concluded that the earth had a real visible surface for millions of years before Newton, Einstein and Hawking and Ed Witten appeared on that surface and began publishing their senseless guesswork about an unnatural invisible void and unnatural invisible gravity, and unnatural invisible quantum particles that could be in multiple unnatural invisible places at the same time, and unnatural invisible finite black holes, and unnatural invisible finite strings.

Logically, Nature must have devised the only visible structure of the real Universe allowable. There am only one visible unified infinite surface occurring eternally in one infinite dimension that am always illuminated mostly by finite non-surface light.

Joe Fisher, Realist

report post as inappropriate

Reality am fundamental. Reality am not theoretical.

My research has concluded that the earth had a real visible surface for millions of years before Newton, Einstein and Hawking and Ed Witten appeared on that surface and began publishing their senseless guesswork about an unnatural invisible void and unnatural invisible gravity, and unnatural invisible quantum particles that could be in multiple unnatural invisible places at the same time, and unnatural invisible finite black holes, and unnatural invisible finite strings.

Logically, Nature must have devised the only visible structure of the real Universe allowable. There am only one visible unified infinite surface occurring eternally in one infinite dimension that am always illuminated mostly by finite non-surface light.

Joe Fisher, Realist

report post as inappropriate

Login or create account to post reply or comment.