View Full Version : Layman's question: ekpyrotic big bang scenario
alistair
May16-04, 09:16 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>In the ekpyrotic big bang scenario two branes collide\nand their kinetic energy creates matter and radiation.\nA homogeneous universe ( uniform cosmic microwave background radiation\ndistribution)only arises if the branes are parallel.Branes that are\nnot parallel can collide repeatedly to produce homogeneity..Will a\nfuture brane collision cause our universe to become more inhomogeneous\nand if so\nwill the inhomogeneity get reduced again as the branes continue to\ncycle between moving together and moving apart?\nAlso, if there were a large number of branes, each with its own\ninitial mass distribution, colliding at all possible angles, could\nthese branes collide just once to produce a homogeneous universe?\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>In the ekpyrotic big bang scenario two branes collide
and their kinetic energy creates matter and radiation.
A homogeneous universe ( uniform cosmic microwave background radiation
distribution)only arises if the branes are parallel.Branes that are
not parallel can collide repeatedly to produce homogeneity..Will a
future brane collision cause our universe to become more inhomogeneous
and if so
will the inhomogeneity get reduced again as the branes continue to
cycle between moving together and moving apart?
Also, if there were a large number of branes, each with its own
initial mass distribution, colliding at all possible angles, could
these branes collide just once to produce a homogeneous universe?
alistair
May16-04, 04:08 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Can the branes in the ekpyrotic scenario move together\nand apart forever like a perpetual motion machine?\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Can the branes in the ekpyrotic scenario move together
and apart forever like a perpetual motion machine?
alistair
Jun9-04, 11:57 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>If one of a colliding pair of D branes was made of antimatter would\nthis mean that there could only be one collision of the branes - Would\nthe branes be destroyed or just the rest mass on them?\n\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>If one of a colliding pair of D branes was made of antimatter would
this mean that there could only be one collision of the branes - Would
the branes be destroyed or just the rest mass on them?
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>sol2 <sol2@physicsforums.com> wrote in message news:<sol2.17k9lh-100000@physicsforums.com>...\n\n> ...Now Steinhardt and Turok say that - according to \'M-theory\' - the\n> universe need not pass through a singularity between a big crunch and a\n> big bang.\n\nThis is Steinhardt\'s claim, but it\'s a tiny minority of cosmologists\nwho follow it because in cyclical cosmology, it\'s still passing\nthrough a singularity, even if you try to call it something else. The\nbrane collision is a singularity by another name. Also, the ekpyrotic\nmodel is different than cyclical cosmology. In the ekpyrotic model,\nthe universe went through an infinite contraction, passed through a\nBig Crunch/Big Bang, and then will expand for eternity. In cyclical\ncosmology, the universe expands, collapses, goes through a Big\nCrunch/Big Bang, expands, collapses, goes through a Big Crunch/Big\nBang, and repeats this an infinite number of times. It would actually\npass through an infinire number of singularities. Yeah, it would also\nbe a perpetual motion machine, which is another argument against it.\nOnce at a physics conference. Steinhardt was defending his cyclical\nmodel, and suddenly Susskind stood up and shouted, "That\'s a perpetual\nmotion machine of the second kind!".\n\nDavid\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>sol2 <sol2@physicsforums.com> wrote in message news:<sol2.17k9lh-100000@physicsforums.com>...
> ...Now Steinhardt and Turok say that - according to 'M-theory' - the
> universe need not pass through a singularity between a big crunch and a
> big bang.
This is Steinhardt's claim, but it's a tiny minority of cosmologists
who follow it because in cyclical cosmology, it's still passing
through a singularity, even if you try to call it something else. The
brane collision is a singularity by another name. Also, the ekpyrotic
model is different than cyclical cosmology. In the ekpyrotic model,
the universe went through an infinite contraction, passed through a
Big Crunch/Big Bang, and then will expand for eternity. In cyclical
cosmology, the universe expands, collapses, goes through a Big
Crunch/Big Bang, expands, collapses, goes through a Big Crunch/Big
Bang, and repeats this an infinite number of times. It would actually
pass through an infinire number of singularities. Yeah, it would also
be a perpetual motion machine, which is another argument against it.
Once at a physics conference. Steinhardt was defending his cyclical
model, and suddenly Susskind stood up and shouted, "That's a perpetual
motion machine of the second kind!".
David
alistair
Jun17-04, 06:55 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>ULMO said:\n\nOnce at a physics conference. Steinhardt was defending his cyclical\nmodel, and suddenly Susskind stood up and shouted, "That\'s a perpetual\nmotion machine of the second kind!".\n\nALISTAIR writes:\n\nIf two branes collide repeatedly, provided they don\'t convert all\ntheir kinetic energy into mass and radiation,as the number of\ncollisions increases, they will not be perpetual motion machines of\nthe second kind.The branes would be in disagreement with the second\nlaw of thermodynamics if they collided and stuck together forever.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>ULMO said:
Once at a physics conference. Steinhardt was defending his cyclical
model, and suddenly Susskind stood up and shouted, "That's a perpetual
motion machine of the second kind!".
ALISTAIR writes:
If two branes collide repeatedly, provided they don't convert all
their kinetic energy into mass and radiation,as the number of
collisions increases, they will not be perpetual motion machines of
the second kind.The branes would be in disagreement with the second
law of thermodynamics if they collided and stuck together forever.
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>alistair <alistair@goforit64.fsnet.co.uk> wrote in message news:<861c1b21.0406171453.1a154eb-100000@posting.google.com>...\n> ULMO said:\n>\n> Once at a physics conference. Steinhardt was defending his cyclical\n> model, and suddenly Susskind stood up and shouted, "That\'s a perpetual\n> motion machine of the second kind!".\n>\n> ALISTAIR writes:\n>\n> If two branes collide repeatedly, provided they don\'t convert all\n> their kinetic energy into mass and radiation,as the number of\n> collisions increases, they will not be perpetual motion machines of\n> the second kind.The branes would be in disagreement with the second\n> law of thermodynamics if they collided and stuck together forever.\n\nCould they do this indefinitely, an infinite number of times?\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>alistair <alistair@goforit64.fsnet.co.uk> wrote in message news:<861c1b21.0406171453.1a154eb-100000@posting.google.com>...
> ULMO said:
>
> Once at a physics conference. Steinhardt was defending his cyclical
> model, and suddenly Susskind stood up and shouted, "That's a perpetual
> motion machine of the second kind!".
>
> ALISTAIR writes:
>
> If two branes collide repeatedly, provided they don't convert all
> their kinetic energy into mass and radiation,as the number of
> collisions increases, they will not be perpetual motion machines of
> the second kind.The branes would be in disagreement with the second
> law of thermodynamics if they collided and stuck together forever.
Could they do this indefinitely, an infinite number of times?
alistair
Jun18-04, 06:49 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>alistair <alistair@goforit64.fsnet.co.uk> wrote in message news:<861c1b21.0406171453.1a154eb-1....google.com>...\n\n> If two branes collide repeatedly, provided they don\'t convert all\n> their kinetic energy into mass and radiation,as the number of\n> collisions increases, they will not be perpetual motion machines of\n> the second kind.The branes would be in disagreement with the second\n> law of thermodynamics if they collided and stuck together forever.\n\nULMO said:\n\n>Could they do this indefinitely, an infinite number of times?\n\nAlistair writes:\n\nThey could if the branes could be shown to be equivalent to a pair of\noscillating particles but the trouble with this idea is that the\nbranes change their rest mass after a collision and the particles of\nan oscillator don\'t collide and don\'t change their rest mass.What\nmakes the branes come together and move apart anyway?\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>alistair <alistair@goforit64.fsnet.co.uk> wrote in message news:<861c1b21.0406171453.1a154eb-1....google.com>...
> If two branes collide repeatedly, provided they don't convert all
> their kinetic energy into mass and radiation,as the number of
> collisions increases, they will not be perpetual motion machines of
> the second kind.The branes would be in disagreement with the second
> law of thermodynamics if they collided and stuck together forever.
ULMO said:
>Could they do this indefinitely, an infinite number of times?
Alistair writes:
They could if the branes could be shown to be equivalent to a pair of
oscillating particles but the trouble with this idea is that the
branes change their rest mass after a collision and the particles of
an oscillator don't collide and don't change their rest mass.What
makes the branes come together and move apart anyway?
alistair
Jun19-04, 12:17 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Alistair wrote:\nWhat makes the branes come together and move apart anyway?\n\nALISTAIR replies:\n\nThe Casimir force between branes could make the branes move apart.\nBut a force which gets stronger with increasing distance would have to\nbring the branes together again.A long distance version of the colour\nforce perhaps!\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Alistair wrote:
What makes the branes come together and move apart anyway?
ALISTAIR replies:
The Casimir force between branes could make the branes move apart.
But a force which gets stronger with increasing distance would have to
bring the branes together again.A long distance version of the colour
force perhaps!
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