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Physics, Astronomy & Cosmology / Why am I having trouble with Tolman's paradox?

« on: 22/06/2014 20:03:43 »

Reference material:

http://www.ejtp.com/articles/ejtpv6i21p1.pdf  (see diagram on page 5)

___

I still cannot see how a tachyon that merely moves faster than light necessarily reverses the order of events. I have been drawing Minkowski diagrams for several hours and I am still not seeing it.  All the diagrams that propose to demonstrate reverse causality merely draw in a tachyon moving backwards in time.  Thus as far as I am concerned they are inserting the conclusion into the premise.  The diagram from page five above is incorrect as far as I am concerned.  All signals traveling from B to A,  (be they tachyon, photon, or sound wave) must traverse from right-to-left going upwards.  Not downwards as tachyon2 was drawn in the PDF. 

Here is the original diagram followed by my correction:



Upon asking a non-expert, I was informed that I must have an accelerated frame whose future contains the past of a stationary observer.   So I did that exact thing.   I see no reverse causality again. Only that the tachyon will arrive prior to the light signal from A0.   The diagram below shows a stationary observer `"A"` and an observer `"B"` in an accelerated reference frame:



I still do not see how reversal of events can happen here. Only when we presume that tachyons "move backwards in time"  does this manifest. But I cannot see how that is asserted merely by a tachyon traversing a more shallow slope on the diagram than the light cone. 

More precisely:  Please explain why the tachyon from observer B to observer A must necessarily move backwards  in time in  ('downwards') the reference frame of A.

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Physics, Astronomy & Cosmology / Wheeler-Dewitt equation in plain english

« on: 27/01/2014 09:40:32 »

I have been studying canonical gravity theories lately and I have encountered the Wheeler-Dewitt equation.  I was wondering if anyone here knows physics well enough to answer some questions I have about that equation.   To the best of my knowledge, I will attempt to translate what the equation says into plain english. My translation is probably wrong.  I would welcome any corrections and the harshest criticism.

We are going to be looking at integrals taken over something called a phase space.  This is different from the so-called "path-integral formulation" of   QFT. Those are usually called  "flat space quantization".   The integral we are taking is the integral of the gravitational field over all possible (static) wave functions of all possible universes. This integral will have an associated functional that will associate the integral with a scalar. Call this scalar the "Hamiltonian Constraint."    The Wheeler-DeWitt equation in english goes:

H(x)|psi> = 0
"The functional over all possible universe phase states, given as a wave function, has a Hamiltonian Constraint equal to zero."

I don't disagree with the validity of that statement.  But I want to really understand what that means.  What sorts of realistic changes would see in a universe where the Hamiltonian Constraint was non-zero?

The only situation in which this equation had any application, that I know of, is in the Hartle-Hawking State. This might mean it is a toy model for cosmology, rather than a description of the universe as it exists now chock full  of galaxies. If I am wrong, correct away as you feel fit!

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Physics, Astronomy & Cosmology / Have you read Emmy Noether's Wonderful Theorem?

« on: 13/09/2013 21:55:24 »

This is a book which covers the relationship between conservation laws and symmetries in physical laws of nature. The book goes into depth about the meanings of Hamiltonian Mechanics and the Euler-Lagrange equation.  The Principle of Least Action is a central theme running through the chapters of the book.   

Has anyone read this or have a copy around?

http://www.amazon.com/Noethers-Wonderful-Theorem-Dwight-Neuenschwander/dp/0801896940

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Physics, Astronomy & Cosmology / Which one of these sentences best depicts the 'Principle of Least Action'?

« on: 13/09/2013 06:27:35 »

Which one of these sentences best depicts the Principle of Least Action? And are any of these completely false?

• A system that is under stress or strain will evolve in such a way as to relieve that stress.
• Physical systems attempt to convert potential energy into kinetic energy as fast as possible.
• The total energy of a system is conserved.
• Physical systems tend to maximize potential energy. (?)
• A physical system evolves in such a way as to keep the the kinetic energy nearly equal to the potential energy, if it can.

Before answering, I'm searching for an underlying philosophical principle, not more equations and more jargon. We all know what the equations say, and we can all go to wikipedia and find out how to define "action" as an integral and then demand the change in the path is a 'stationary point' in terms of calculus of variations. Yes and yes. We all know this already. We can bog each other down in jargon until we are blue in the face. But I'm trying to pin down what the equations MEAN in terms of the ontology and dynamics of the physical world.

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New Theories / description of my research

« on: 12/08/2013 19:18:58 »

In 2009 I completed a piece of software inspired by Ken Stauffer's Evolve4.0c.  These simulations are called "ecosystem simulations" because they are genetic algorithms performed in "real space" with organisms who must live out their lives in an environment.   We use simple grid worlds to perform this simulation, because evolution is gratuitously slow, and desktop computers are limited in power.   Superficially, this research is categorized as "Artificial Life" , or ALife.

There are two styles of  ALife to speak of. One is the 1990s-styled Alife, and the other is 21st century Alife. 

In the 1990s-styled Alife sim, the organisms are given high-level actions to perform in the environment such as "ATTACK" and "EAT", or most embarrassingly, "REPRODUCE".   These are actions normally associated with entities who live in video games.  Regardless of this roughshod approach, those simulations did actually exhibit Darwinian natural selection, and they would self-perpetuate for weeks on end.  1990s-styled ALife stands as proof-of-principle for natural selection actually working the way scientists say it does.

21st-century styled Alife will henceforth be called 21C-Alife for short.  In rudimentary form, the simulation will primarily be concerned with some sort of "machine" which builds a copy of itself.  In these simulations we do not take for granted behaviors as eating or even reproducing.  An "attack" command would not be allowed.   Instead we want eating to actually physically be performed by the simulation's kinematics. Reproducing does not happen instantly, instead the organisms within the simulation have the duty of actually constructing  a copy of themselves in realtime from parts.  Things like "eating" are then seen as very abstract actions.  "Eating" is the machine selecting and discarding portions of the environment that it takes into itself through a pore in its body ("mouth").  Abstractly, "eating" is a form of discrimination of the environmental material by the organism/machine. In most cases the concept of "body" is also abstract here.

Despite the name I have given, 21C,  initial work on this was done by John Von Neumann in the 1950s. He wanted a cellular automaton that could reproduce a copy of itself,  with the target of the research being the question "Can a machine build a copy of itself?".   Von Neumann showed the answer to that question is yes. 

For decades, this research floundered and went ignored.  Very recently it has been picked up again by Tim Hutton, Robert Freitas, Ralph Merkle, and myself.  There is a parallel research tract being done by biochemists to produce a nano-scale protocell using real DNA, PNA, or similar.  It is my opinion that both approaches should inform one another. 

A number of foundational questions lie at the center of this research.

• What is the qualitative difference between the self-replication seen in crystal growth, versus the replication of offspring from a stored string/data/genotype?   In the most abstract, mathematical descriptions of self-replication, we can assert that the various branches of a snowflake are "copies of themselves".  But that seems to be lacking something; some je ne sais quoi, which we understand only intuitively. Can we quantify this intuitive notion?    Progress on this question may involve deeper understanding of the relationship between form and function.
• What precisely is the difference between raw material to be eaten for the purposes of building up parts of a machine's body, versus the machine's body?  In other words, how random does the "soup of raw materials" need to be for the machine to be said to be "constructing" itself to begin with?    This question is asking for a quantitative answer to what the verb "to construct" actually means.
• The existence of self-replicators has two questions. Existence question 1.  Can replicators only exist in our universe at the molecular level?
• Existence question 2.  Molecular self-replicators exist. Look out your window to see a tree.  That was easy to confirm.  However, trees have no eyes, no central nervous system, and they do not copy themselves through the use of levers, arms, or grippers.  Pushing the proverbial pendulum to the far extreme, we can imagine factories wherein the human engineers have been replaced by powerful artificial intelligence Androids, complete with hand-eye coordination,  complex memories, and language.  So we have a spectrum with two trivial answers standing at the poles.  Molecular self-assembly, "Tree-like" replication on one end, and powerful androids working factories at the opposite end.  Existence question 2 asks, are there any plausible replicators between these two extremums?   

In regards to the existence question no.2,  it is the opinion of this author that Von Nuemann's constructor strongly suggests that there can exist such a replicator between the two trivial extremes. That machine would be an artifact operating at "macro" scales that is capable of building a high-fidelity copy of itself.  Its manifestation in reality may end up being smaller than can be seen with the human eye, (but still significantly larger than molecules) and some early versions may have to replicate underwater.

Starting from a discipline of computer simulation, an ALife simulation containing self-replicating constructors is desired. And this simulation raises questions about how large the "genotype/data/tape" would need to be relative to the size of the rest of the machine.  Orthodox approaches derived from Von Neumann usually have the tape's information in identical size to the rest of the machine's parts, but this requirement is not strict.  This is seen in the videos linked in citation.

In any case, this research is highly interdisciplinary, and so the citations are drawn from branches of science that are widely separated. 


Citations

http://en.wikipedia.org/wiki/Von_Neumann_universal_constructor

{book} Kinematic Self-Replicating Machines (Landes Bioscience, 2004) ISBN 1-57059-690-5

For comprehensive citations see, http://www.thenakedscientists.com/forum/index.php?topic=48610.0

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New Theories / interdisciplinary science forums

« on: 09/08/2013 21:06:00 »

I was wondering if anyone knew a place on the internet where people discuss science and technology topics that are interdisciplinary. I would like a place where people actually read the books that are brought up and are capable of genuinely discussing the material inside those books. I'm currently working on material that is included within the following publications. I want to apply the material in them to actual simulations or chemical lab experiments (if necessary). I cannot simply sit alone in a room and just read books. I need to "bounce ideas" of those who understand what I am asking and what I am working on.

The materials I am currently working with are listed here:

• Kinematic Self-Replicating Machines , (Freitas Jr. R.A., Merkle R.C. ), (Landes Bioscience 2004), ISBN-10: 1570596905, ISBN-13: 978-1570596902
•   Biology's First Law: The Tendency for Diversity and Complexity to Increase in Evolutionary Systems , ( McShea D.W. , Brandon R.N.), (University Of Chicago Press 2010), ISBN-10: 0226562263, ISBN-13: 978-0226562261
•   Principles of Life , (Ganti, T), ( Oxford University Press USA 2003), ISBN-10: 0198507267, ISBN-13: 978-0198507260
•   Protocells. Bridging Living and Non-living Matter , (Rasmussen S., Bedau M.A.), ( MIT Press, Nov.2008), ISBN: 9780262182683
•   Signs Of Life. How Complexity Pervades Biology , (Sole R., Goodwin B. ), (Basic Books, Jan.2002), ISBN-10: 0465019285, ISBN-13: 978-0465019281
•   Chemical Evolution and the Origin of Life , (Rauchfuss H.) , (Springer, Dec.2008) ISBN-10: 3540788220, ISBN-13: 978-3540788225
•   The Origin of Species , (Darwin, C.), (Barnes & Noble Classics, Dec.2003), ISBN-10: 1593080778, ISBN-13: 978-1593080778
  

Like to talk to someone who has read at least one of these and is ready to discuss. I would be tickled pink. Thanks.

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Just Chat! / Intelligence as an Illusion?

« on: 22/02/2008 00:29:07 »

Originally posted by Hadrian
This all shows us just how we and the planet are miss served by our illusion of human inelegance.

While I agree that humans can be very inelegant, I assume the word you wanted was intelligence.

Making this substitution, I would agree that much of our intelligence is illusory (this is part of the trouble in trying to define artificial intelligence, that we can never really get to grips with how illusory our own intelligence is).  The problem is that simply removing that illusion does not give us the intelligence we lack.

I'd love to talk more about this topic. 
Intelligence is an illusion? Are you taking a behaviorist stance here?  Something else?  Please expand!

_{MOD EDIT - See below}

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Just Chat! / IEEE pubs

« on: 17/02/2008 01:53:41 »

Can anyone here help me "obtain" this article??  (: hint::hint: )

http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/9982/32055/01490957.pdf?arnumber=1490957

 [8D]

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Physics, Astronomy & Cosmology / Dark Matter and string theory

« on: 15/02/2008 03:35:06 »

Brian Greene has suggested that the relative weakness of gravity can be attributed to the fact that gravity leaks into the other "branes" which can be considered parallel universes right next to our own.

It seems logical, then, that matter in the other universes also leaks into this one, causing gravitational effects that would appear to come from "nowhere".    What is the general consensus among string theorists with regards to dark matter?   Has anyone considered its gravity to be that of extra-braneal mass leaking their gravity into our 4D local brane?

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Just Chat! / Artificial Intelligence

« on: 15/02/2008 03:28:02 »

   I'd like to find a place on the internet to exchange ideas with people about AI, but I have studied it such an extensive level that it is difficult to find anyone. The only things that I can stand to spend my time reading are actual academic publications. But those are a one-way street where one posts and another reads. There is no EXCHANGE of ideas.

Does anyone have some good links to AI discussion forums? I have speant hours googling to no avail. I am not interested in the SingInst. And the comp.ai.* newsgroups have all been overrun by trolls and grad students "calling for all papers" for seminars on campuses that are hundreds of miles away from me.

Thanks for your help.