From Marcin.Hajduk w astri.uni.torun.pl Mon Dec 2 14:36:15 2002 From: Marcin.Hajduk w astri.uni.torun.pl (Marcin Hajduk) Date: Mon, 2 Dec 2002 14:36:15 +0100 (CET) Subject: virtual particles In-Reply-To: <200211132359.35420.tomlacz@astri.uni.torun.pl> Message-ID: Hello! I've got (perhaps silly) a short question. Vacuum is fulfilled by virtual particles (especially photons - I suppose). According to Heisenberg uncertainty principle - dE*dt>h/4*Pi or something like that. So virtual particle with energy dE exist dt seconds (in case there's no other particles nor magnetic field which could give for the virtual photon enough of energy to make it real). But energy of virtual particles is real. So can it influence on evolution of Universe? Can virtual particles appear in all points of space simultaneously? ,-,-, ,-, ,- ,- , ,. , ' ' ' '-- ' '- ' ' " From Bartosz.Lew w astri.uni.torun.pl Mon Dec 2 15:31:52 2002 From: Bartosz.Lew w astri.uni.torun.pl (Bartosz Lew) Date: Mon, 2 Dec 2002 15:31:52 +0100 (CET) Subject: virtual particles In-Reply-To: Message-ID: hi I think that virtual parcicles were introduced so they could explain some mechanims and stuff and to have such a thing that doesn't interact with (unless some special conditions - strong grav. fields in black holes outskirts) with nothing and doesn't influence on anything since they live so short. So in such approach this energy (which would be positive) even if maeybe real we cannot use in any way nor even distinguish it's presence (which is why we call the energy virtual). afterall I think we have enough problems with DE, DM, labmda, that why to bother with another form of energy :) ps. if I know well virtual particles borrow some energy from spacetime so this new positive energy would be balanced with some negative-energy debt in space, I quess. In case of no fields, virtual particles which appear always with their anitparticle counterpart would anihilate (canceling their bills with space) before rest of the world would realised (noticed) that anything happened. pozdrawiam ******************************************************************************* Bartosz Lew e-mail: szajtan w astri.uni.torun.pl szajtan w phys.uni.torun.pl Centrum Astronomii UMK szajtan w poczta.onet.pl TORUN, POLAND www: http://www.phys.uni.torun.pl/~szajtan ******************************************************************************* On Mon, 2 Dec 2002, Marcin Hajduk wrote: > Hello! > > I've got (perhaps silly) a short question. Vacuum is fulfilled by virtual > particles (especially photons - I suppose). According to Heisenberg > uncertainty principle - dE*dt>h/4*Pi or something like that. So virtual > particle with energy dE exist dt seconds (in case there's no other particles > nor magnetic field which could give for the virtual photon enough of energy > to make it real). But energy of virtual particles is real. So can it > influence on evolution of Universe? Can virtual particles appear in all > points of space simultaneously? > > ,-,-, ,-, ,- ,- , ,. , > ' ' ' '-- ' '- ' ' " > > From szajtan w poczta.onet.pl Fri Dec 6 14:00:18 2002 From: szajtan w poczta.onet.pl (szajtan odwieczny) Date: Fri, 6 Dec 2002 14:00:18 +0100 Subject: fishing net Message-ID: <000a01c29d27$79b84500$24b11d3e@szajtan> hello everybody. Got an idea to share. Once upon a time I thought about such a thing. What was observed are the great voids (of size about 100 Mly in diameter or even bigger) separated by some cosmic great scale structures so it altogether looks like a soap foam. Assuming that the voids are empty, than the curvature of out local part of the Universe would look like - example in 2d: as we were pumping the balloon but confined by a fishing net which doesn't allow the surface of the balloon for free expansion, and in the end the balloon is quizzed by the strings of the net but it out stands in the holes of the net between the strings. In 3d this would be little more complicated to imagine but what do you thing about this ? with best holiday greetings Bartek --------------r-e-k-l-a-m-a----------------- Masz dość płacenia prowizji bankowi ? mBank - załóż konto http://epieniadze.onet.pl/mbank -------------- następna część --------- Załącznik HTML został usunięty... URL: From michalf w ncac.torun.pl Fri Dec 6 14:00:31 2002 From: michalf w ncac.torun.pl (Michal Frackowiak) Date: Fri, 06 Dec 2002 14:00:31 +0100 Subject: fishing net References: <000a01c29d27$79b84500$24b11d3e@szajtan> Message-ID: <3DF09F6F.40707@ncac.torun.pl> szajtan odwieczny wrote: > hello everybody. Got an idea to share. > Once upon a time I thought about such a thing. > > What was observed are the great voids (of size about 100 Mly in > diameter or even bigger) separated by some cosmic great scale > structures so it altogether looks like a soap foam. Assuming that the > voids are empty, than the curvature of out local part of the > Universe would look like - example in 2d: as we were pumping the > balloon but confined by a fishing net which doesn't allow the surface > of the balloon for free expansion, and in the end the balloon is > quizzed by the strings of the net but it out stands in the holes of > the net between the strings. In 3d this would be little more > complicated to imagine but what do you thing about this ? > that is correct. curvature is constant only in homogeneous universe. in the perturbed one it is not. but deviations are really small. good luck michal From boud w astro.uni.torun.pl Wed Dec 11 12:49:23 2002 From: boud w astro.uni.torun.pl (Boud Roukema) Date: Wed, 11 Dec 2002 12:49:23 +0100 (MET) Subject: andrzej: wyklad jest 12:40-14:40 poniedz. Message-ID: Cze�� Andzrej, This semester it's a bit late anyway, but you can see the correct time of the wyk�ad monographiczny here: http://www.astro.uni.torun.pl/sympa/shape-univ/ Sorry about the misunderstanding. pozdrawiam boud From boud w astro.uni.torun.pl Fri Dec 13 13:11:19 2002 From: boud w astro.uni.torun.pl (Boud Roukema) Date: Fri, 13 Dec 2002 13:11:19 +0100 (MET) Subject: fishing net In-Reply-To: <3DF09F6F.40707@ncac.torun.pl> Message-ID: Cze�� wszystkim, It's a nice analogy :). Of course, just like nearly any analogy, this one is not perfect. As Micha� said, it's true that the deviations from homogeneity are small on scales anything much bigger than the Schwarzschild horizon of a SMBH http://adjani.astro.uni.torun.pl:9673/zwicky/SuperMBH Another problem is that in the 2D balloon, the positive fluctuations (the net) are connected in a continuous network, while the negative fluctuations (lowest density) are unconnected, separated from one another. In the standard (3D) model, at early times the + and - fluctuations are typically of the same typical sizes (e.g. from the hypothesis of "gaussian fluctuations"), and the 2D topology of contours of constant density ("genus analysis") is connected both for + and - fluctns. If you consider all matter more dense than some value, - a low density value gives a "gruyere (ser) topology" - a critical density values gives a "sponge topology" - a high density gives a "meatball topology" This is impossible to do with a balloon, which is 2D, since the topology of constant density "1-surfaces" is 1D. But I still like the analogy, because it gives a feeling of the constraint caused by positive matter density. na razie boud On Fri, 6 Dec 2002, Michal Frackowiak wrote: > szajtan odwieczny wrote: > > > hello everybody. Got an idea to share. > > Once upon a time I thought about such a thing. > > > > What was observed are the great voids (of size about 100 Mly in > > diameter or even bigger) separated by some cosmic great scale > > structures so it altogether looks like a soap foam. Assuming that the > > voids are empty, than the curvature of out local part of the > > Universe would look like - example in 2d: as we were pumping the > > balloon but confined by a fishing net which doesn't allow the surface > > of the balloon for free expansion, and in the end the balloon is > > quizzed by the strings of the net but it out stands in the holes of > > the net between the strings. In 3d this would be little more > > complicated to imagine but what do you thing about this ? > > > > that is correct. curvature is constant only in homogeneous universe. in > the perturbed one it is not. but deviations are really small. > good luck > michal > > From szajtan w poczta.onet.pl Fri Dec 13 17:53:03 2002 From: szajtan w poczta.onet.pl (szajtan odwieczny) Date: Fri, 13 Dec 2002 17:53:03 +0100 Subject: military masking net References: Message-ID: <002601c2a2c8$2042c1c0$14ae1d3e@szajtan> > As Michaウ said, it's true that the deviations from homogeneity are > small on scales anything much bigger than the Schwarzschild horizon of > a SMBH http://adjani.astro.uni.torun.pl:9673/zwicky/SuperMBH > > Another problem is that in the 2D balloon, the positive fluctuations > (the net) are connected in a continuous network, while the negative > fluctuations (lowest density) are unconnected, separated from one > another. Why do you consider that as a problem. That's just what we observe, isn't it. Those great cosmic scale filaments extending for hundredths of Mpcs. > > In the standard (3D) model, at early times the + and - fluctuations > are typically of the same typical sizes (e.g. from the hypothesis of > "gaussian fluctuations"), and the 2D topology of contours of constant > density ("genus analysis") is connected both for + and - fluctns. agreed but in time the curvature evolves, like everything else in this Universe. In time, because of gravity, matter tends to gather in a strings or clumps of higher density, and thus the curvature changes. > > If you consider all matter more dense than some value, > - a low density value gives a "gruyere (ser) topology" > - a critical density values gives a "sponge topology" what is the difference between these two ? is it only about the thickness of strings ? > - a high density gives a "meatball topology" > > This is impossible to do with a balloon, which is 2D, since the > topology of constant density "1-surfaces" is 1D. Let's consider a cross section of a large part of the universe with a plain. Then we take a pencil and draw all the contours of a constant matter density (= constant curvature) on that plane. We make a little step back to see the picture. We will see some distinctive pattern similar to the one observed for clusters of galaxies. This is the analogy to that net on the balloon. But strings of the net are not 1D but 2D (they have width) and in reality 3D, so for the fishing net we should sometimes even fill up some gaps not allowing the balloon the out stand. This I should call now a military masking net. The constraint of 2D balloon is as you mentioned that - fluctuations are separated. That's right but this is only because that on 2d surface a circle splits it into two regions. So in general this is not a good model. In 3D we can easily jump from one loop into another, unless there are walls (also those from that masking net :) but in 3D) - like The Great Wall. na razie bartek. --------------r-e-k-l-a-m-a----------------- Masz dosc placenia prowizji bankowi ? mBank - zaloz konto http://epieniadze.onet.pl/mbank From boud w astro.uni.torun.pl Mon Dec 16 16:57:53 2002 From: boud w astro.uni.torun.pl (boud roukema) Date: Mon, 16 Dec 2002 16:57:53 +0100 (MET) Subject: military masking net In-Reply-To: <002601c2a2c8$2042c1c0$14ae1d3e@szajtan> Message-ID: Cze��, On Fri, 13 Dec 2002, szajtan odwieczny wrote: > > As Micha$B%&(B said, it's true that the deviations from homogeneity > are > > small on scales anything much bigger than the Schwarzschild horizon of > > a SMBH http://adjani.astro.uni.torun.pl:9673/zwicky/SuperMBH > > > > > > Another problem is that in the 2D balloon, the positive fluctuations > > (the net) are connected in a continuous network, while the negative > > fluctuations (lowest density) are unconnected, separated from one > > another. > > Why do you consider that as a problem. That's just what we observe, isn't > it. > Those great cosmic scale filaments extending for hundredths of Mpcs. I probably didn't write this carefully! There is no problem with the + fluctuations being connected! The problem is that the voids are unconnected in the analogy. In reality, the voids are connected. The very low density parts of space also form a filamentary network, connecting the lowest density points to each other. If we start with a nice N-body simulation film, and substitute densities rho -> 2 - rho and then put in the same colour pattern for the new densities, it should look on average similar to before, at least at low density thresholds and early times. (There is a difference on very high densities, at late times - "non-linear scales" - once there are densities greater than 2, it is clear that there cannot be perfect symmetry between + and - fluctuations.) > > In the standard (3D) model, at early times the + and - fluctuations > > are typically of the same typical sizes (e.g. from the hypothesis of > > "gaussian fluctuations"), and the 2D topology of contours of constant > > density ("genus analysis") is connected both for + and - fluctns. > > agreed > but in time the curvature evolves, like everything else in this Universe. > In time, because of gravity, matter tends to gather in a strings or clumps > of > higher density, and thus the curvature changes. OK, fine. > > If you consider all matter more dense than some value, > > - a low density value gives a "gruyere (ser) topology" > > - a critical density values gives a "sponge topology" > > what is the difference between these two ? between all three: gruyere: high density regions connected; low density UNconnected sponge: high density regions connected; low density connected meatball: high density regions UNconnected; low density connected > is it only about the thickness of strings ? > > > - a high density gives a "meatball topology" > > > > This is impossible to do with a balloon, which is 2D, since the > > topology of constant density "1-surfaces" is 1D. > > Let's consider a cross section of a large part of the universe with a plain. "plane" > Then we take a pencil and draw all the contours > of a constant matter density (= constant curvature) on that plane. We make a > little step back to see the picture. We will see some distinctive pattern > similar to the one observed for clusters of galaxies. This is the analogy to > that net on the balloon. But strings of the net are not 1D but 2D (they have > width) and in reality 3D, so for the fishing net we should sometimes even > fill up some gaps not allowing the balloon the out stand. This I should call > now a military masking net. The constraint of 2D balloon is as you mentioned > that > - fluctuations are separated. That's right but this is only because that on > 2d surface a circle splits it into two regions. So in general this is not a Agreed. > good model. In 3D we can easily jump from one loop into another, unless > there are walls (also those from that masking net :) but in 3D) - like The > Great Wall. OK. BTW, sometimes people get confused between this sort of topology (topology of 2D surfaces of constant density) and 3D topology of comoving space. Including some cosmologists like Richard Gott III who have published on both subjects ;). na razie boud