tag:blogger.com,1999:blog-4212234230338648875.post7842743309282096625..comments2024-03-18T19:27:16.659-07:00Comments on The Eternal Universe: Symmetry for the "I don't want a PhD in Physics to understand that" PeopleJoseph Smidthttp://www.blogger.com/profile/02583891162785742138noreply@blogger.comBlogger12125tag:blogger.com,1999:blog-4212234230338648875.post-75491757187861558002011-09-25T15:58:21.098-07:002011-09-25T15:58:21.098-07:00What if what we call recorded history has had a se...What if what we call recorded history has had a series of forward flows in time followed by backward flows in time? Also postulate that each individual flow of time at the beginning of the Big Bang almost equally cancelled one another out. With the staggering number of cycles of forward and backward flow since the Big Bang, would not the minute difference in these flows accumulate to give the net forward flow of time we observe on the macrosopic level today. Is there any mathematical model in support of this hypothesis?Ea649502noreply@blogger.comtag:blogger.com,1999:blog-4212234230338648875.post-19912209367765503182010-06-16T01:46:24.040-07:002010-06-16T01:46:24.040-07:00I think that time reversal symmetry is a key eleme...I think that time reversal symmetry is a key element in the creation of the universe. If nothing exists before the start of the Universe, there is no time. We imagine this state to be a quantum supposition of all states with time reversal symmetry. These are considered to be the "no time" states since time flowing one way is balanced by time flowing the other way. The supposition state spontaneously decays - no cause - and one of the supposition states becomes real. We have a real Universe in which time reversal symmetry holds. If the time reversal symmetry is spontaneously broken - these things happen - we get a universe with one way time. There is no way of knowing which Universe will be the final result - it is a random selection - except by observing the current Universe.plafferty@mail.comnoreply@blogger.comtag:blogger.com,1999:blog-4212234230338648875.post-79439269441871074512010-06-07T01:46:45.564-07:002010-06-07T01:46:45.564-07:00Has anyone else seen the colour of air or sat atop...Has anyone else seen the colour of air or sat atop of and looked down into the enlightened gravity of the "UnBeheld"? {otherwise known as the "Akashic Records","The Universal Pool Of Conciousness"}and be almost pulled into its sence of belonging that we all want and need.(its easy to ignore what we truly need when were blinded by lobbyists and complacency lol)Universal Rebelhttps://www.blogger.com/profile/17343689645952682986noreply@blogger.comtag:blogger.com,1999:blog-4212234230338648875.post-59085107933030267772010-03-05T08:35:00.215-08:002010-03-05T08:35:00.215-08:00Bryan, interesting food for thought. I have somet...Bryan, interesting food for thought. I have something new to dwell on today.Joseph Smidthttps://www.blogger.com/profile/02583891162785742138noreply@blogger.comtag:blogger.com,1999:blog-4212234230338648875.post-36071762822401626332010-03-05T08:12:54.523-08:002010-03-05T08:12:54.523-08:00To put the point in terms of your picture: It'...To put the point in terms of your picture: It's an empirical fact whether or not something in the world can be described by the tree-shape on the left. And it's a mathematical fact that the tree-shape on the left is invariant under a certain reversal transformation defined <em>on the tree-shape</em>. What is missing is a well-motivated account of what that reversal transformation means <em>in the world</em>.Bryanhttps://www.blogger.com/profile/07379669532781325751noreply@blogger.comtag:blogger.com,1999:blog-4212234230338648875.post-56390277344674974992010-03-05T07:39:36.133-08:002010-03-05T07:39:36.133-08:00Thanks -- I'm willing to grant that physical t...Thanks -- I'm willing to grant that physical theories are more than instrumental models. They describe the world. And it's an empirical fact whether or not the world can be modeled by a given Lagrangian. Moreover, it's just a mathematical fact whether or not a Lagrangian exhibits CPT invariance -- given a particular conventional definition of C, P and T. But why choose any particular definition of C, P or T? Answering your question of whether or not the universe "really has these symmetries" requires us to come up with a well-motivated (not just conventional) definition of what these symmetries mean "in the world." The difficulty is that there's no real operation that corresponds to "implementing T" or "implementing P" -- so it seems we must seek some other justification for their definition. Only then can we be justified in saying the *world* is CPT-invariant, and not just our physical theories.Bryanhttps://www.blogger.com/profile/07379669532781325751noreply@blogger.comtag:blogger.com,1999:blog-4212234230338648875.post-19370739331492058092010-03-05T07:22:02.170-08:002010-03-05T07:22:02.170-08:00Hi Bryan,
"More generally, how can we possib...Hi Bryan,<br /><br />"More generally, how can we possibly motivate any of our definitions of T, C and P? We could start by just assuming that the world is reversible."<br /><br />Good question.<br /><br />I may not be able to answer your concern, but saying the world has CPT invariance translates to only allowing terms in your Lagrangian with CPT invariance. Then, we calculate the equations of motion, cross sections, decays rates, etc... from this Lagrangian and compare with experiment.<br /><br />If what we observe doesn't match, we need to have either more or less terms. If we need more, this means the restriction of only allowing CPT terms is too harsh. This translates to CPT being violated. This would let us "know" the world is not CPT invariant.<br /><br />However, a CPT invariant Lagrangian does match observation so now we need to ask: Is this because the universe really has these symmetries or is it <br /><a href="http://theeternaluniverse.blogspot.com/2010/03/are-physical-theories-just-models.html" rel="nofollow">just coincidence</a>.?Joseph Smidthttps://www.blogger.com/profile/02583891162785742138noreply@blogger.comtag:blogger.com,1999:blog-4212234230338648875.post-68940933737308623552010-03-05T07:07:15.563-08:002010-03-05T07:07:15.563-08:00But how can one define precisely what it means to ...But how can one define precisely what it means to "reverse the flow of time"? More generally, how can we possibly motivate any of our definitions of T, C and P? We could start by just assuming that the world is reversible. If fundamental physics is both deterministic and time-translation invariant, then there is always *some* involution under which the equations are time-reversal invariant as well. In the standard model, that involution is CPT symmetry. But that would just beg the question -- we want to *know* if the world is reversible, without just assuming it from the start!Bryanhttps://www.blogger.com/profile/07379669532781325751noreply@blogger.comtag:blogger.com,1999:blog-4212234230338648875.post-77422784176193728322010-03-01T12:36:19.731-08:002010-03-01T12:36:19.731-08:00As for linking CPT to the arrow of time, I don'...As for linking CPT to the arrow of time, I don't have anything intelligent to say.<br /><br />However, a complete breaking of CPT is related to a violation of Lorentz invariance.Joseph Smidthttps://www.blogger.com/profile/02583891162785742138noreply@blogger.comtag:blogger.com,1999:blog-4212234230338648875.post-1851247883804234422010-03-01T12:10:06.570-08:002010-03-01T12:10:06.570-08:00I'm not aware of any proposed mechanism linkin...I'm not aware of any proposed mechanism linking particle physics CPT-violations (e.g. Kaon decay) with the thermodynamic arrow of time (related to entropy). Thoughts?Ben Pratthttp://www.millennialstar.orgnoreply@blogger.comtag:blogger.com,1999:blog-4212234230338648875.post-45276025577540408692010-03-01T09:35:33.097-08:002010-03-01T09:35:33.097-08:00Nice piece. Have been thinking about the nature of...Nice piece. Have been thinking about the nature of charge while writing about the structure of atoms. Nicely summed up!James Haytonhttp://10minus9.wordpress.comnoreply@blogger.comtag:blogger.com,1999:blog-4212234230338648875.post-78220320121957868832010-02-27T18:36:53.598-08:002010-02-27T18:36:53.598-08:00Wow, pretty extensive article on CPT. Well done. ...Wow, pretty extensive article on CPT. Well done. I like the picture as it is very helpful.<br /><br />For those who don't know, there are more symmetries than C, P and T but these three are very important. <br /><br />Great post Quantumleap42!Joseph Smidthttps://www.blogger.com/profile/02583891162785742138noreply@blogger.com