The Pauli Exclusion Principle and SU(2) vs. SO(3) in Loop Quantum Gravity

Recent attempts to resolve the ambiguity in the loop quantum gravity description of the quantization of area has led to the idea that j=1 edges of spin-networks dominate in their contribution to black hole areas as opposed to j=1/2 which would naively be expected. This suggests that the true gauge group involved might be SO(3) rather than SU(2) with attendant difficulties. We argue that the assumption that a version of the Pauli principle is present in loop quantum gravity allows one to maintain SU(2) as the gauge group while still naturally achieving the desired suppression of spin-1/2 punctures. Areas come from j=1 punctures rather than j=1/2 punctures for much the same reason that photons lead to macroscopic classically observable fields while electrons do not.Comment: This paper received an "honorable mention" in the 2003 Essay Competition of the Gravity Research Foundation and should be appearing in a special issue of Int. J. Mod. Phys.

Letter from Benj[amin] I. Wheeler to John Muir, 1903 Mar 24.

UNIVERSITY OF CALIFORNIAOFFICE OF THE PRESIDENTBerkeley, March 24, 1903.My dear Mr. Muir:—The President has telegraphed asking for the detailed plan of his trip in the Yosemite. I have sent him an outline; I have not told him that you could not come, for I confidently believe it will be arranged all right; indeed, cannot be otherwise. The orderliness of nature will not allow so fit a plan to fail. My plan is that the President should leave his car at Raymond on the morning of Friday, May 15th, and proceed with his whole party to the Big Trees, reaching there at three or four in the afternoon. Without anyone\u27S knowing it or noticing it you two could then slip away into the woods and the rest of the party would go on by stage to Wawona, and the next day to the Sentinel Hotel. I have thought it might be well for you to take young Joe LeConte as cook and guide; possibly, however, we could have LeConte go with the rest of the party, and give you a man whom Mr. A. S. Mann, the Secretary of Washburn Brothers, has recommended to me as a man who is particularly well acquainted with that region and particularly well able to take care of the horses, food, etc. Evidently the President does not want a crowd along; he may not want anybody besides yourself.Very faithfully yours,[illegible]Mr. John Muir,Martinez,California.[03192

Letter from Benj[amin] I. Wheeler to John Muir, 1903 Mar 21.

UNIVERSITY OF CALIFORNIAOFFICE OF THE PRESIDENTBerkeley, March 21, 1903.My dear Mr. Muir:—What I telephoned you today I would like to repeat in written form. The opportunity of spending three or four days in the forests of the Yosemite with the President, who is the most enthusiastic lover of nature, I will warrant, you ever met, seems to me a thing which you surely ought not to let fail. I talked with the President some months ago about his outing in California, and he decided that he wanted to have a look at the California forests and uplands, and to have it as a total release from the worries and flurries of official life. (He has concluded that he would like to have you go with him alone.) You might, and probably would, take with you a man to \u27nip cook and take care of things. Joseph LeConte is ready to do this if you wish him to. As you know he is quiet and unobtrusive, and would really, while helping you very greatly, be less in the way than any other guide could be. I hope you will not let the trip-round-the-world people deprive you of the pleasure I know you would have, and rob the President of the United States of his cherished plan. I am sure that these people the moment they know they have to will change the arrangements easily. (The President will arrive at Raymond by special train Friday morning, May 15th, and leaves the following Monday night.) We have planned that he with the rest of his company should go on with us to the Big Trees, and at that point you and he should separate yourselves from the company and lose yourselves in the woods, rejoining us the following Monday.Very faithfully yours,[illegible]Mr. John Muir,Martinez, California.[03190

Accurate "superluminal" transmission via entanglement, superoscillations and quasi-Dirac distributions

We analyse a system in which, due to entanglement between the spin and spatial degrees of freedom, the reduced transmitted state has the shape of the freely propagating pulse translated in the complex co-ordinate plane. In the case an apparently "superluminal" advancement of the pulse the delay amplitude distribution is found to be a peculiar approximation to the Dirac delta-function, and the transmission coefficient exhibits a well-defined super-oscillatory window. Analogies with potential tunnelling and the Wheeler's delayed choice experiment are highlighted

Second bound state of PsH

The existence of a second bound state of PsH that is electronically stable and also stable against positron annihilation by the normal 2gamma and 3gamma processes is demonstrated by explicit calculation. The state can be found in the 2,4So symmetries with the two electrons in a spin triplet state. The binding energy against dissociation into the H(2p) + Ps(2p) channel was 6.06x10-4 Hartree. The dominant decay mode of the states will be radiative decay into a configuration that autoionizes or undergoes positron annihilation. The NaPs system of the same symmetry is also electronically stable with a binding energy of 1.553x10-3 Hartree with respect to the Na(3p) + Ps(2p) channel.Comment: 4 pages, 2 figures, RevTex styl

Three-Dimensional Gravity and String Ghosts

It is known that much of the structure of string theory can be derived from three-dimensional topological field theory and gravity. We show here that, at least for simple topologies, the string diffeomorphism ghosts can also be explained in terms of three-dimensional physics.Comment: 6 page

Infrared spectrum and stability of a π-type hydrogen-bonded complex between the OH and C2H2 reactants

A hydrogen-bonded complex between the hydroxyl radical and acetylene has been stabilized in the reactant channel well leading to the addition reaction and characterized by infrared action spectroscopy in the OH overtone region. Analysis of the rotational band structure associated with the a-type transition observed at 6885.53(1) cm−1 (origin) reveals a T-shaped structure with a 3.327(5) Å separation between the centers of mass of the monomer constituents. The OH (v = 1) product states populated following vibrational predissociation show that dissociation proceeds by two mechanisms: intramolecular vibrational to rotational energy transfer and intermolecular vibrational energy transfer. The highest observed OH product state establishes an upper limit of 956 cm−1 for the stability of the π-type hydrogen-bonded complex. The experimental results are in good accord with the intermolecular distance and well depth at the T-shaped minimum energy configuration obtained from complementary ab initio calculations, which were carried out at the restricted coupled cluster singles, doubles, noniterative triples level of theory with extrapolation to the complete basis set limit

The Mass Dependance of Satellite Quenching in Milky Way-like Halos

Using the Sloan Digital Sky Survey, we examine the quenching of satellite galaxies around isolated Milky Way-like hosts in the local Universe. We find that the efficiency of satellite quenching around isolated galaxies is low and roughly constant over two orders of magnitude in satellite stellar mass ($M_{*}$ = $10^{8.5}-10^{10.5} \, M_{\odot}$), with only $\sim~20\%$ of systems quenched as a result of environmental processes. While largely independent of satellite stellar mass, satellite quenching does exhibit clear dependence on the properties of the host. We show that satellites of passive hosts are substantially more likely to be quenched than those of star-forming hosts, and we present evidence that more massive halos quench their satellites more efficiently. These results extend trends seen previously in more massive host halos and for higher satellite masses. Taken together, it appears that galaxies with stellar masses larger than about $10^{8}~M_{\odot}$ are uniformly resistant to environmental quenching, with the relative harshness of the host environment likely serving as the primary driver of satellite quenching. At lower stellar masses ($< 10^{8}~M_{\odot}$), however, observations of the Local Group suggest that the vast majority of satellite galaxies are quenched, potentially pointing towards a characteristic satellite mass scale below which quenching efficiency increases dramatically.Comment: 14 pages, 8 figure