Search FQXi


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.

Contests Home

Current Essay Contest


Contest Partners: Fetzer Franklin Fund, and The Peter and Patricia Gruber Foundation

Previous Contests

Undecidability, Uncomputability, and Unpredictability Essay Contest
December 24, 2019 - April 24, 2020
Contest Partners: Fetzer Franklin Fund, and The Peter and Patricia Gruber Foundation
read/discusswinners

What Is “Fundamental”
October 28, 2017 to January 22, 2018
Sponsored by the Fetzer Franklin Fund and The Peter & Patricia Gruber Foundation
read/discusswinners

Wandering Towards a Goal
How can mindless mathematical laws give rise to aims and intention?
December 2, 2016 to March 3, 2017
Contest Partner: The Peter and Patricia Gruber Fund.
read/discusswinners

Trick or Truth: The Mysterious Connection Between Physics and Mathematics
Contest Partners: Nanotronics Imaging, The Peter and Patricia Gruber Foundation, and The John Templeton Foundation
Media Partner: Scientific American

read/discusswinners

How Should Humanity Steer the Future?
January 9, 2014 - August 31, 2014
Contest Partners: Jaan Tallinn, The Peter and Patricia Gruber Foundation, The John Templeton Foundation, and Scientific American
read/discusswinners

It From Bit or Bit From It
March 25 - June 28, 2013
Contest Partners: The Gruber Foundation, J. Templeton Foundation, and Scientific American
read/discusswinners

Questioning the Foundations
Which of Our Basic Physical Assumptions Are Wrong?
May 24 - August 31, 2012
Contest Partners: The Peter and Patricia Gruber Foundation, SubMeta, and Scientific American
read/discusswinners

Is Reality Digital or Analog?
November 2010 - February 2011
Contest Partners: The Peter and Patricia Gruber Foundation and Scientific American
read/discusswinners

What's Ultimately Possible in Physics?
May - October 2009
Contest Partners: Astrid and Bruce McWilliams
read/discusswinners

The Nature of Time
August - December 2008
read/discusswinners

Forum Home
Introduction
Terms of Use

Order posts by:
 chronological order
 most recent first

Posts by the author are highlighted in orange; posts by FQXi Members are highlighted in blue.

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

 RSS feed | RSS help
RECENT POSTS IN THIS TOPIC

Ding Jia: on 5/12/20 at 22:40pm UTC, wrote Dear David, Thanks for your interest and sorry for the delayed response. ...

David Jewson: on 5/6/20 at 7:43am UTC, wrote Dear Ding, It looks to me as if a lot of work has gone into some lovely...

Ding Jia: on 5/5/20 at 19:39pm UTC, wrote Hi Luca, Thanks for your interest! One opportunity for phenomenological...

Luca Valeri: on 5/4/20 at 7:42am UTC, wrote Hi Ding Jia, Thanks for letting us in having a peak on your research of...

Ding Jia: on 4/25/20 at 0:08am UTC, wrote Essay Abstract I argue for the presence of indefinite spacetime...


RECENT FORUM POSTS

Georgina Woodward: "That is about the 'anatomy"" of spacetime." in Anatomy of spacetime and...

Lorraine Ford: "So what exactly is WRONG with physics, apart from the fact that physics..." in The Present State of...

Georgina Woodward: "The perception generated of time difference relates to the potential..." in Anatomy of spacetime and...

Steve Dufourny: "Hello Jim, yes indeed in a sense we have these motions and we have invented..." in The Quantum Clock-Maker...

Jim Snowdon: "Hi Steve, Clearly we have motion in our Universe. It is not..." in The Quantum Clock-Maker...

Steve Dufourny: "You are welcome, thanks too for your words. I have never lost the faith..." in The Present State of...

Georgina Woodward: "Thank you. Good luck." in The Nature of Time

Lorraine Ford: "Rob, As you have not replied, I take it that you now concede that the..." in 16th Marcel Grossmann...


RECENT ARTICLES
click titles to read articles

The Quantum Clock-Maker Investigating COVID-19, Causality, and the Trouble with AI
Sally Shrapnel, a quantum physicist and medical practitioner, on her experiments into cause-and-effect that could help us understand time’s arrow—and build better healthcare algorithms.

Connect the Quantum Dots for a New Kind of Fuel
'Artificial atoms' allow physicists to manipulate individual electrons—and could help to reduce energy wastage in electronic devices.

Can Choices Curve Spacetime?
Two teams are developing ways to detect quantum-gravitational effects in the lab.

The Quantum Engine That Simultaneously Heats and Cools
Tiny device could help boost quantum electronics.

The Quantum Refrigerator
A tiny cooling device could help rewrite the thermodynamic rule book for quantum machines.


FQXi FORUM
September 17, 2021

CATEGORY: Undecidability, Uncomputability, and Unpredictability Essay Contest (2019-2020) [back]
TOPIC: Indefinite causal structure can enhance predictability by Ding Jia [refresh]
Bookmark and Share
Login or create account to post reply or comment.

Author Ding Jia wrote on Apr. 25, 2020 @ 00:08 GMT
Essay Abstract

I argue for the presence of indefinite spacetime causal structure in nature, and show how it removes predictability obstacles regarding 1) spacetime singularities, 2) ultra-high energy quantum field theory, and 3) quantum gravitational computations.

Author Bio

Ding Jia is a PhD student at Perimeter Institute for Theoretical Physics and University of Waterloo.

Download Essay PDF File

Bookmark and Share


Luca Valeri wrote on May. 4, 2020 @ 07:42 GMT
Hi Ding Jia,

Thanks for letting us in having a peak on your research of indefinite causal structure. I followed Lucien Hardy's work on operational approaches to physics a while and found it very interesting. But sadly I was never able to take the time to follow him in his roads to quantum gravity.

Can you make some qualitative phenomenological prediction that might follow from a indefinite causal structure? The causal structure seems to be somehow a priori in the sense that it is difficult (impossible?) to express scientific experience in a non definite causal structure. On the other hand it is surely good to critically question principles that might restrict the physical inquiry.

In my essay I argue that a causal description of events might be complementary to a realistic one (assignment of properties independently of a measurement).

During the work on my essay, where I tried study the conceptual structure of physics, I was speculating that gravity prevents the ability to define strictly separable free objects. And this might be the cause, why perturbative quantum field theoretical approaches might fail to renormalizable with a finite set of observable quantities.

Your essay surely deserves more attention a it seems to get.

Luca

Bookmark and Share
report post as inappropriate
Author Ding Jia replied on May. 5, 2020 @ 19:39 GMT
Hi Luca,

Thanks for your interest!

One opportunity for phenomenological prediction is the cosmological primordial spectrum. Maybe indefinite causal structure plays a role in generating the correlations in CMB fluctuations.

Doing physics in the absence of definite spacetime structure belongs to the greater effort of doing physics in the absence of a preferred spacetime background. I think the contributions of generations of physicists to this pursuit of "background independence" has made the task with indefinite causal structure much easier than it could otherwise be.

Your essay looks quite interesting. I will put a post there if I gather any thought or question worth sharing.

Related to your thoughts on renormalizability, I think quantum gravity prevents an assignment of definite spacetime distance to events/objects due to the superposition of spacetimes in a gravitational path integral. Regarding the failure of perturbative quantum gravity, my guess is that it is due to using propagators which depend on the spacetime distance with respect to some fixed the background spacetime, which obscures the superposition of spacetime distances.

Best,

Ding

Bookmark and Share


David Jewson wrote on May. 6, 2020 @ 07:43 GMT
Dear Ding,

It looks to me as if a lot of work has gone into some lovely original ideas. Well done.

I have taken a particular interest in Feynman’s path integral method. Although I would guess you would find it unbelievable, I think that both Special and General Relativity can be mathematically derived using Feynman's method. Therefore, I one hundred percent agree with you about indefiniteness actually being an essential part of those theories. I also agree with your principal of causal neutrality, but I think it works better where laws of physics are replaced a simple algorithm that can be used to predict Nature, and it is that algorithm that produces indefiniteness.

I’ve explained it in more detail in my essay. Old Seth clearly liked to look at things differently and it seems to me that that there is an alternative way Feynman’s maths can be used to interpret Nature completely differently. Interesting if you like being unconventional!

It must be great working at the Warterloo Institute! idea

All the best,

David

Bookmark and Share
report post as inappropriate
Author Ding Jia replied on May. 12, 2020 @ 22:40 GMT
Dear David,

Thanks for your interest and sorry for the delayed response.

The idea of using Feynman’s path integral to derive Relativity sounds quite intriguing! Could you offer more details or point to a reference with more details?

Best,

Ding

Bookmark and Share


Login or create account to post reply or comment.

Please enter your e-mail address:
Note: Joining the FQXi mailing list does not give you a login account or constitute membership in the organization.