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排序方式: 共有130条查询结果,搜索用时 15 毫秒
121.
Edward Witten 《Nuclear Physics B》1982,195(3):481-492
It is argued that the ground state of the Kaluza-Klein unified theory is unstable against a process of semiclassical barrier penetration. This is related to the fact that the positive energy conjecture does not hold for the Kaluza-Klein theory; an explicit counter-example is given. The reasoning presented here assumes that in general relativity one should include manifolds of non-vacuum topology. It is argued that the existence of elementary fermions (not present in the original Kaluza-Klein theory) would stabilize the Kaluza-Klein vacuum. 相似文献
122.
Edward Witten 《Nuclear Physics B》1978,145(1):110-118
In the two-dimensional SU(N) Thirring model, the 1/N expansion seems to predict spontaneous breaking of the continuous chiral symmetry. This is impossible in two-dimensions. Reasoning along the lines of Berezinski, Kosterlitz and Thouless for the two-dimensional XY model, we argue that, in fact, rather than showing long-range order, vanishes in this model as |x|?1/N at large |x|. The 1/N expansion is, in fact, a rather good guide to the properties of this model. 相似文献
123.
124.
Edward Witten 《Communications in Mathematical Physics》1987,109(4):525-536
It is shown that in elliptic cohomology — as recently formulated in the mathematical literature — the supercharge of the supersymmetric nonlinear signa model plays a role similar to the role of the Dirac operator inK-theory. This leads to several insights concerning both elliptic cohomology and string theory. Some of the relevant calculations have been done previously by Schellekens and Warner in a different context.Supported in part by NSF grants PHY 80-19754 and PHY 86-16129 相似文献
125.
Edward Witten 《Nuclear Physics B》1990,330(2-3):285-346
It is known that the Jones polynomial of knot theory, and its generalizations, are closely related to the integrable “vertex models” of two-dimensional statistical mechanics, and to quantum groups. In this paper, an attempt is made to show on a priori grounds, starting only from general covariance of three-dimensional Chern-Simons gauge theory and two-dimensional “duality”, why this must be so. 相似文献
126.
Edward Witten 《Nuclear Physics B》1996,460(3):541-559
A long-standing puzzle about the heterotic string has been what happens when an instanton shrinks to zero size. It is argued here that the answer at the quantum level is that an extra SU(2) gauge symmetry appears that is supported in the core of the instanton. Thus in particular the quantum heterotic string has vacua with higher rank than is possible in conformal field theory. When k instantons collapse at the same point, the enhanced gauge symmetry is Sp(k). These results, which can be tested by comparison to Dirichlet five-branes of Type I superstrings and to the ADHM construction of instantons, give the first example for the heterotic string of a non-perturbative phenomenon that cannot be turned off by making the coupling smaller. They have applications to several interesting puzzles about string duality. 相似文献
127.
N.D. Gabitzsch G.S. Mutchler C.R. Fletcher E.V. Hungerford L. Coulson D. Mann T. Witten M. Furić G.C. Phillips B. Mayes L.Y. Lee J. Hudomalj J.C. Alfred C. Goodman 《Physics letters. [Part B]》1973,47(3):234-236
The π+ total nuclear cross sections for 9Be, 12C, 16O, and 27Al have been measured in the energy range 114 to 210 MeV, while π? data have been taken at 153 MeV. In the center-of-mass coordinate system the π-nucleus total cross sections reach their maximum value near the π-nucleon resonance (TπC.M.= 1.52 MeV) where they scale as . The measured total cross sections exhibit considerable broadening with respect to the π-nucleon resonance. 相似文献
128.
W. M. Reiff E. H. Witten J. Takacs J. H. Zhang C. C. Torardi 《Hyperfine Interactions》1990,56(1-4):1723-1728
The extremes of single ion slow paramagnetic relaxation and cooperative 3D-antiferromagnetic order are exemplified in a series
of structurally characterized complexes based on the anhydrous FeCl3-α-di-imine system. “Soft” Cl−Cl contacts, C−C (π-π) and hydrogen bonding interactions are found to lead to surprisingly strong
magnetic exchange among five and six coordinate high-spin iron III monomers. The latter form the building blocks of novel
“double chain” polymer magnets held together via the preceding “weak” interactions. 相似文献
129.
We show that QCD with a sufficient number of fermions of zero bare mass has physical massless particles. That result also follows from triangle anomalies, so only our method is novel. Our method involves proving special cases of recently conjectured paramagnetic inequalities for fermions. The proofs are simple applications of the Atiyah-Patodi-Singer theorem on spectral flow.Supported in part by the National Science Foundation Grant No. PHY80-19754Supported in part by DOE Grant No. DE-AC02-76ER02220 相似文献
130.
The apparently intractable shape of a fold in a compressed elastic film lying on a fluid substrate is found to have an exact solution. Such systems buckle at a nonzero wave vector set by the bending stiffness of the film and the weight of the substrate fluid. Our solution describes the entire progression from a weakly displaced sinusoidal buckling to a single large fold that contacts itself. The pressure decrease is exactly quadratic in the lateral displacement. We identify a complex wave vector whose magnitude remains invariant with compression. 相似文献