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Natural Science Forum / Physics / Research / December 2007A Stringy Nature Needs Just Two Constants
In PF, Marcus notes: "I see that the whole contents of EPL from July thru December 1986 is free to download until the end of the year. If you (or anyone else) sees any other paper that might be of special historical interest, please let us know" Really this is the situation of some journals, whose free window closes in December, or in July and December. So it is a good month to notice it and point our relevant papers not in the ArXiV. The paper I was intrigued about is http://www.iop.org/EJ/abstract/0295-5075/2/3/006 ================================== A Stringy Nature Needs Just Two Constants G. Veneziano CERN - Geneva, Switzerland Abstract. Dual string theories of everything, being purely geometrical, contain only two fundamental constants: c, for relativistic invariance, and a length l, for quantization. Planck's and Newton's constants appear only through Planck's length, a "calculable" fraction of l. Only the existence of a light sector breaks a "reciprocity" principle and unification at l, which is also the theory's cut-off. ================================== The paper somehow rejects Planck constant, telling that measured quantities can be related to Compton lengths instead. So he only needs Planck lenght and c. Or Planck length and Planck time, as the quotient produces c. Pretty strange paper. On Dec 4, 3:08 pm, "ariv...@unizar.es" <Al.Riv...@gmail.com> wrote: > In PF, Marcus notes: > "I see that the whole contents of EPL from July thru December 1986 is [quoted text clipped - 31 lines] > > Pretty strange paper. i think it is part of this conversation: http://xxx.lanl.gov/abs/physics/0110060 "Trialogue on the number of fundamental constants" between the author (GV) and Michael Duff and Lev Okun. in some manner Duff might say i belong to the "4-constant" party (because i think that electric charge is a unique dimension of physical stuff alongside time, length, and mass), but actually i agree with Duff pretty much completely. there are maybe about 26 "fundamental constants" (John Baez has enumerated them here: http://math.ucr.edu/home/baez/constants.html ) and they are all dimensionless. i don't see "c" or "G" or "hbar" or "epsilon0" as being fundamental constants, but are just a reflection of the units of length, time, mass, and charge that we humans have decided to use. i do think that the Planck time, Planck length, Planck mass, and Planck charge *do* represent units of scale that are fundamental and preferred by Nature (or, at least, the same with a factor of sqrt(4*pi) tossed in, because i think it's better to normalize 4*pi*G rather than just G and it's better to normalize epsilon0 rather than 4*pi*epsilon0 so that "flux density" and "field strength" are the same thing in vacuo and Gauss's Law is the most simplified). and i don't know diddley about string theory, but i would think that any physical theory can be scaled in such a way that Planck units are the units which makes "c", "G", "hbar", and "4*pi*epsilon0" all equal to one. then they just go away in expressions of physical law, and any numbers that remain are truly fundamental constants. r b-j > i think it is part of this conversation: > > http://xxx.lanl.gov/abs/physics/0110060 > "Trialogue on the number of fundamental constants" > > between the author (GV) and Michael Duff and Lev Okun. Thanks for the link to this very interesting paper. I am finding the contribution by M. Duff most convincing. It is in the spirit of a paper by J.M Levy-Leblond, Riv. Nuovo Cimento, Vol.7, 188 (1977) which had much influence on me. Levy-Leblond sated that our progress in understanding the nature follows the direction of eliminating from theories various (inessential) numerical constants with the improper name "fundamental" constants. In fact those constants are merely the constants which result from our unnatural choice of units, the choice due to our incomplete understanding of the unified theory behind. > and i don't know diddley about string theory, but i would think that > any physical theory can be scaled in such a way that Planck units are > the units which makes "c", "G", "hbar", and "4*pi*epsilon0" all equal > to one. then they just go away in expressions of physical law, and > any numbers that remain are truly fundamental constants. It is precisely what I played with. So I calculated the conversion factors between the MKSA units and the units in which those four constants are equal to one. It is incredibly useful in actual calculations. So I am using those tables whenever I wish to do some numerical work with the quantities entering the equations, which may be written in the units in which c=G=1, or in the units in which c=G=hbar=1, etc. One can simply put all fundamental constants to one, perform calculations in the units in which c=G=hbar=4 pi epsilon =1, and then convert the result into MKSA units. Calling those units in which all four constants are equal to one units D, one has 1D = (\hbar c/G)^{1/2} = 2.1768269 \times 10^{-8}$ kg 1D = (\hbar G/c^5)^{1/2} = 5.3903605 \times 10^{-44} s 1D = (\hbar G/c^3)^{1/2} = 1.6159894 \times 10^{-35} m 1D = (4 \pi \epsilon_0 \hbar c)^{1/2} = \alpha^{-1/2} e = 1.8755619 \times 10^{-18} As 1D = c^3 (4 \pi \epsilon_0/G)^{1/2} = 3.4794723 \times 10^{25} A 1D = c^2 (4 \pi \epsilon_0 G)^{-1/2} = 1.0431195 \times 10^{27} V 1D = c^2 (\hbar c/G)^{1/2} = 1.9564344 \time 10^{9} J 1D = 1.41702 \times 10^{32} {}^0 K I first published this (together with some discussion of how various physical quantities transform under dilations) in Appendix of my book "The Landscape of Theoretical Physics: A Global View; From Point Particles to the Brane World and Beyond, in Search of a Unifying Principles" (Kluwer, May 2001) which is now available on arXiv: http://arxiv.org/abs/gr-qc/0610061 >On Dec 4, 3:08 pm, "ariv...@unizar.es" <Al.Riv...@gmail.com> wrote: >> In PF, Marcus notes: [quoted text clipped - 65 lines] > >r b-j Baez' article is quite useless. It has a list of the names of masses etc. without numbers or units. You say "John Baez has enumerated them (26) here: http://math.ucr.edu/home/baez/constants.html ) and they are all dimensionless". The fact that he left off all attributes excepting their title does not make them dimensionless. It makes them useless. Then Baez says: "But in the grand scheme of things, units are not very important". Au contraire, in PHYSICS, they are everything. In mathematics they are nothing. John Polasek > Baez' article is quite useless. that's pretty brave thing to say. > It has a list of the names of masses > etc. without numbers or units. i asked him once what they are expressed against: http://groups.google.com/group/sci.physics.research/browse_frm/thread/8951d35e69 e3a8bd/1adf7cd4d3297ae9#1adf7cd4d3297ae9 and he answered likely the Planck Mass. > You say "John Baez has enumerated them > (26) here:http://math.ucr.edu/home/baez/constants.html) and they are > all dimensionless". > The fact that he left off all attributes what attributes do you mean? the mass of a particle is a mass. when normalized against a natural unit of mass, you get a number. do you mean inertial mass vs. gravitational mass? > excepting their title does > not make them dimensionless. you don't understand. > It makes them useless. you don't understand. > Then Baez says: "But in the grand scheme of things, units are not very > important". Au contraire, in PHYSICS, they are everything. the objects and interactions in Nature do not give a rat's a.s what units we, or the Europeans, or the aliens on the planet Zog happen to use for units of measure. > In mathematics they are nothing. it's been said: "Mathematicians routinely ignore units but engineers do so at their peril." i tread pretty lightly in this newsgroup (less so at comp.dsp, it might be entertaining if you come over there and tell us what we're doing thats all wrong, it's not moderated) since i am not a physicist. i would not imagine that the confidence you have in your own understanding of the topic what is fundamental or not in nature is shared by others here (some reasonably heaviweight physicists), but i'll not speak for them. r b-j |
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