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Old 2008-04-19, 19:15   #1
xilman
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Default Quantum field theory

Around 1980, Nobel laureate Steven Weinberg went on the lecture circuit. I was just a lowly (chemistry) grad student when he reached Oxford. During his lecture he recounted the standard mechanical model to illustrate how particles may interact by exchanging virtual particles. He observed that the standard model was a purely repulsive force and offered to buy a drink for anyone who could produce an attractive force by particle exchange.

if you've not seen the standard model, it goes like this. Fit two tennis players with rollerskates and let them hit and return tennis balls to each other. When a player hits a ball, the momentum they impart to the ball means that they roll away from the net. As the game progresses, both players recede from the net and so from each other. An observer who can not see the tennis balls concludes that the players are subject to a repulsive force.

After the lecture, a small gaggle of audience members, including myself and Roger Penrose, went down to the front to expound their ideas. Roger went before me and his idea was rather cute. Consider a tennis match played in a tank of water. The players are wearing breating apparatus and are standing on the ceiling. As tennis balls are less dense than water, hitting one of them imparts negative net momentum...

Steven Weinberg then explained that what he really wanted was a game played between men and women whereby men attracted women, and vice versa, but same-sex couples repelled each other. Nobody then present had a solution.

After thinking about the problem off and on for almost 30 years, I recently came up with a solution. Steven Weinberg has now sent me an email acknowledging that he owes me a drink. I won't reveal my solution so that you have a chance of solving the problem.


Paul
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Old 2008-04-19, 19:32   #2
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To add unnecessary muddying of the water here, I recall
that the motion of the a viscosity-free fluid contributes the
mass of half the volume of fluid the ball displaces to these scenarios.

Last fiddled with by davieddy on 2008-04-19 at 20:22
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Old 2008-04-19, 20:16   #3
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Quote:
Originally Posted by xilman View Post
Steven Weinberg then explained that what he really wanted was a game played between men and women whereby men attracted women, and vice versa, but same-sex couples repelled each other.Paul
Can't resist:
I think there is at least one thread catering for this ATM
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Old 2008-04-20, 07:54   #4
xilman
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Quote:
Originally Posted by davieddy View Post
Can't resist:
I think there is at least one thread catering for this ATM
Indeed. I wondered whether to include a reference to it myself but thought it would distract from the statement of the problem.


Paul
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Old 2008-04-20, 15:18   #5
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There may be homosexual animals, but have you seen
a homosexual proton?

BTW I think I read a good answer to the problem in
a semi-popular book, but damned if I can remember it.
My first instinct says "negative mass" but photons
are massless. Hope your answer will be illuminating.

BTW2 I hate the description of the Higg's field as
some sort of treacle. Viscosity opposes velocity,
whereas mass opposes change in velocity.

David

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Old 2008-04-20, 15:37   #6
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Quote:
Originally Posted by xilman View Post
Steven Weinberg then explained that what he really wanted was a game played between men and women whereby men attracted women, and vice versa, but same-sex couples repelled each other.
The game of life, when played in a Muslim country, would seem to fit.
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Old 2008-04-20, 15:55   #7
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Quote:
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The game of life, when played in a Muslim country, would seem to fit.
You are heading for a Fatwah mate.

Init

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Old 2008-04-20, 21:24   #8
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http://www.writeidea.org/2008/04/gov...lement-on.html

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Old 2008-04-21, 13:55   #9
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Quote:
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You are heading for a Fatwah mate.
You mean that merely stating the truth can get me a fatwah? I want one, I've never been fatwahed before.
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Old 2008-04-21, 16:19   #10
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Wouldn't Richard Feynman's hypothetical spin-2 gravity-force-carrying graviton qualify as a mediator of such an attractive virtual particle exchange?
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Old 2008-04-21, 20:26   #11
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Quote:
Originally Posted by xilman View Post
If you've not seen the standard model, it goes like this. Fit two tennis players with rollerskates and let them hit and return tennis balls to each other. When a player hits a ball, the momentum they impart to the ball means that they roll away from the net. As the game progresses, both players recede from the net and so from each other. An observer who can not see the tennis balls concludes that the players are subject to a repulsive force.
Paul
An intriguing presentation of the problem. Very neat. So far, I'm stumped; do we get a full 30 years to ponder it, or is there an earlier deadline?

I'm wondering if it can be done with something akin to the wave-particle duality of light. Maybe the tennis ball has different propoperties when hit between different-sex players than when hit between same-sex players, in the same way that light appears to have the properties of a particle in certain experiments, but has properties of a wave in others.

Stumped, but pondering...

Norm
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