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arXivPlanckScale Physics and Solutions to the Strong CP Problem without Axion Z. G. Berezhiani, R. N. Mohapatra, G. Senjanovic... more(3) 19921231 We analyse the impact of quantum gravity on the possible solutions to the strong CP problem which utilize the spontaneously broken discrete symmetries, such as parity and time reversal invariance. We find that the stability of the solution under Planck scale effects provides an upper limit on the scale $\Lambda$ of relevant symmetry breaking. This result is model dependent and the bound is most restrictive for the seesaw type models of fermion masses, with $\Lambda < 10^6$ GeV.
Subject Source arXiv URL https://arxiv.org/abs/hepph/9212318view Article Title PlanckScale Physics and Solutions to the Strong CP Problem without AxionAuthors Z. G. Berezhiani; R. N. Mohapatra; G. SenjanovicAbstract We analyse the impact of quantum gravity on the possible solutions to the strong CP problem which utilize the spontaneously broken discrete symmetries, such as parity and time reversal invariance. We find that the stability of the solution under Planck scale effects provides an upper limit on the scale $\Lambda$ of relevant symmetry breaking. This result is model dependent and the bound is most restrictive for the seesaw type models of fermion masses, with $\Lambda < 10^6$ GeV.Is Part Of Phys.Rev.D47:55655570,1993 19921231 Identifier ISSN: DOI 10.1103/PhysRevD.47.5565Category hepphLicense 
arXivTwo Populations and Models of Gamma Ray Bursts J. I. Katz 19921231 Gammaray burst statistics are best explained by a source population at cosmological distances, while spectroscopy and intensity histories of some individual bursts imply an origin on Galactic neutron stars. To resolve this inconsistency I suggest the presence of two populations, one at cosmological distances and the other Galactic. I build on ideas of Shemi and Piran (1990) and of M\'esz\'aros and Rees (1993) involving the interaction of fireball debris with surrounding clouds to explain the observed intensity histories in bursts at cosmological distances. The distances to the Galactic population are undetermined because they are too few to affect the statistics of intensity and direction; I explain them as resulting from magnetic reconnection in neutron star magnetospheres.
Subject Source arXiv URL https://arxiv.org/abs/astroph/9212006view Article Title Two Populations and Models of Gamma Ray BurstsAuthors J. I. KatzAbstract Gammaray burst statistics are best explained by a source population at cosmological distances, while spectroscopy and intensity histories of some individual bursts imply an origin on Galactic neutron stars. To resolve this inconsistency I suggest the presence of two populations, one at cosmological distances and the other Galactic. I build on ideas of Shemi and Piran (1990) and of M\'esz\'aros and Rees (1993) involving the interaction of fireball debris with surrounding clouds to explain the observed intensity histories in bursts at cosmological distances. The distances to the Galactic population are undetermined because they are too few to affect the statistics of intensity and direction; I explain them as resulting from magnetic reconnection in neutron star magnetospheres.Is Part Of Astrophys.J. 422 (1994) 248 19921231 Identifier ISSN: DOI 10.1086/173723Category astrophLicense 
arXivHomogeneous functions on light cones: the infinitesimal structure of some degenerate principal series representations Roger E. Howe 19921231 In this paper we study the reducibility, composition series and unitarity of the components of some degenerate principal series representations of $\RMO(p,q)$, $\RMU(p,q)$ and $\SP(p,q)$. This is done by realizing these representations in paces of homogeneous functions on light cones and writing down the explicit actions of the universal enveloping algebra of the group concerned.
Subject 수학 Source arXiv URL https://arxiv.org/abs/math/9301214view Article Title Homogeneous functions on light cones: the infinitesimal structure of some degenerate principal series representationsAuthors Roger E. HoweAbstract In this paper we study the reducibility, composition series and unitarity of the components of some degenerate principal series representations of $\RMO(p,q)$, $\RMU(p,q)$ and $\SP(p,q)$. This is done by realizing these representations in paces of homogeneous functions on light cones and writing down the explicit actions of the universal enveloping algebra of the group concerned.Is Part Of Bull. Amer. Math. Soc. (N.S.) 28 (1993) 174 19921231 Identifier ISSN: Category math.RTLicense 
arXivSingularities of the Radon transform Alexander G. Ramm, Alexander I. Zaslavsky 19921231 Singularities of the Radon transform of a piecewise smooth function $f(x)$, $x\in R^n$, $n\geq 2$, are calculated. If the singularities of the Radon transform are known, then the equations of the surfaces of discontinuity of $f(x)$ are calculated by applying the Legendre transform to the functions, which appear in the equations of the discontinuity surfaces of the Radon transform of $f(x)$; examples are given. Numerical aspects of the problem of finding discontinuities of $f(x)$, given the discontinuities of its Radon transform, are discussed.
Subject 수학 Source arXiv URL https://arxiv.org/abs/math/9301215view Article Title Singularities of the Radon transformAuthors Alexander G. Ramm; Alexander I. ZaslavskyAbstract Singularities of the Radon transform of a piecewise smooth function $f(x)$, $x\in R^n$, $n\geq 2$, are calculated. If the singularities of the Radon transform are known, then the equations of the surfaces of discontinuity of $f(x)$ are calculated by applying the Legendre transform to the functions, which appear in the equations of the discontinuity surfaces of the Radon transform of $f(x)$; examples are given. Numerical aspects of the problem of finding discontinuities of $f(x)$, given the discontinuities of its Radon transform, are discussed.Is Part Of Bull. Amer. Math. Soc. (N.S.) 28 (1993) 109115 19921231 Identifier ISSN: Category math.CALicense 
arXivParagrassmann Extensions of the Virasoro Algebra A. T. Filippov, A. P. Isaev, A. B. Kurdikov... more(3) 19921231 The paragrassmann calculus proposed earlier is applied to constructing paraconformal transformations and paragrassmann generalizations of the VirasoroNeveuSchwarzRamond algebras.
Subject Source arXiv URL https://arxiv.org/abs/hepth/9212157view Article Title Paragrassmann Extensions of the Virasoro AlgebraAuthors A. T. Filippov; A. P. Isaev; A. B. KurdikovAbstract The paragrassmann calculus proposed earlier is applied to constructing paraconformal transformations and paragrassmann generalizations of the VirasoroNeveuSchwarzRamond algebras.Is Part Of Int. J. Mod. Phys. A8 (1993) 49735004 19921231 Identifier ISSN: DOI 10.1142/S0217751X93001958Category hepthLicense 
arXivA new result for the porous medium equation derived from the Ricci flow LangFang Wu 19921231 Given $\Bbb R^2, $ with a ``good'' complete metric, we show that the unique solution of the Ricci flow approaches a soliton at time infinity. Solitons are solutions of the Ricci flow, which move only by diffeomorphism. The Ricci flow on $\Bbb R^2$ is the limiting case of the porous medium equation when $m$ is zero. The results in the Ricci flow may therefore be interpreted as sufficient conditions on the initial data, which guarantee that the corresponding unique solution for the porous medium equation on the entire plane asymptotically behaves like a ``solitonsolution''.
Subject 수학 Source arXiv URL https://arxiv.org/abs/math/9301218view Article Title A new result for the porous medium equation derived from the Ricci flowAuthors LangFang WuAbstract Given $\Bbb R^2, $ with a ``good'' complete metric, we show that the unique solution of the Ricci flow approaches a soliton at time infinity. Solitons are solutions of the Ricci flow, which move only by diffeomorphism. The Ricci flow on $\Bbb R^2$ is the limiting case of the porous medium equation when $m$ is zero. The results in the Ricci flow may therefore be interpreted as sufficient conditions on the initial data, which guarantee that the corresponding unique solution for the porous medium equation on the entire plane asymptotically behaves like a ``solitonsolution''.Is Part Of Bull. Amer. Math. Soc. (N.S.) 28 (1993) 9094 19921231 Identifier ISSN: Category math.APLicense 
arXivA Fredholm Operator Approach To Morita Equivalence Ruy Exel 19921231 Given C*algebras A and B and an imprimitivity ABbimodule X, we construct an explicit isomorphism X_* : K_i(A) > K_i(B) where K_i denote the complex Ktheory functors for i=0, 1. Our techniques do not require separability nor existence of countable approximate identities. We thus extend, to general C*algebras, the result of Brown, Green and Rieffel according to which strongly Morita equivalent C*algebras have isomorphic Kgroups. The method employed includes a study of Fredholm operators on Hilbert modules.
Subject 수학 Source arXiv URL https://arxiv.org/abs/functan/9212005view Article Title A Fredholm Operator Approach To Morita EquivalenceAuthors Ruy ExelAbstract Given C*algebras A and B and an imprimitivity ABbimodule X, we construct an explicit isomorphism X_* : K_i(A) > K_i(B) where K_i denote the complex Ktheory functors for i=0, 1. Our techniques do not require separability nor existence of countable approximate identities. We thus extend, to general C*algebras, the result of Brown, Green and Rieffel according to which strongly Morita equivalent C*algebras have isomorphic Kgroups. The method employed includes a study of Fredholm operators on Hilbert modules.Is Part Of 19921231 Identifier ISSN: Category functan math.OALicense 
arXivBest uniform rational approximation of $x^\alpha$ on $[0,1]$ Herbert Stahl 19921231 A strong error estimate for the uniform rational approximation of $x^\alpha$ on $[0,1]$ is given, and its proof is sketched. Let $E_{nn}(x^\alpha,[0,1])$ denote the minimal approximation error in the uniform norm. Then it is shown that $$\lim_{n\to\infty}e^{2\pi\sqrt{\alpha n}}E_{nn}(x^\alpha,[0,1]) = 4^{1+\alpha}\sin\pi\alpha$$ holds true for each $\alpha>0$.
Subject 수학 Source arXiv URL https://arxiv.org/abs/math/9301217view Article Title Best uniform rational approximation of $x^\alpha$ on $[0,1]$Authors Herbert StahlAbstract A strong error estimate for the uniform rational approximation of $x^\alpha$ on $[0,1]$ is given, and its proof is sketched. Let $E_{nn}(x^\alpha,[0,1])$ denote the minimal approximation error in the uniform norm. Then it is shown that $$\lim_{n\to\infty}e^{2\pi\sqrt{\alpha n}}E_{nn}(x^\alpha,[0,1]) = 4^{1+\alpha}\sin\pi\alpha$$ holds true for each $\alpha>0$.Is Part Of Bull. Amer. Math. Soc. (N.S.) 28 (1993) 116122 19921231 Identifier ISSN: Category math.CALicense 
arXivLinkless embeddings of graphs in $3$space Neil Robertson, Paul Seymour, Robin Thomas... more(3) 19921231 We announce results about flat (linkless) embeddings of graphs in 3space. A piecewiselinear embedding of a graph in 3space is called {\it flat} if every circuit of the graph bounds a disk disjoint from the rest of the graph. We have shown: (i) An embedding is flat if and only if the fundamental group of the complement in 3space of the embedding of every subgraph is free. (ii) If two flat embeddings of the same graph are not ambient isotopic, then they differ on a subdivision of $K_5$ or $K_{3,3}$. (iii) Any flat embedding of a graph can be transformed to any other flat embedding of the same graph by ``3switches'', an analog of 2switches from the theory of planar embeddings. In particular, any two flat embeddings of a 4connected graph are either ambient isotopic, or one is ambient isotopic to a mirror image of the other. (iv) A graph has a flat embedding if and only if it has no minor isomorphic to one of seven specified graphs. These are the graphs that can be obtained from $K_6$ by means of $Y\Delta$ and $\Delta Y$exchanges.
Subject 수학 Source arXiv URL https://arxiv.org/abs/math/9301216view Article Title Linkless embeddings of graphs in $3$spaceAuthors Neil Robertson; Paul Seymour; Robin ThomasAbstract We announce results about flat (linkless) embeddings of graphs in 3space. A piecewiselinear embedding of a graph in 3space is called {\it flat} if every circuit of the graph bounds a disk disjoint from the rest of the graph. We have shown: (i) An embedding is flat if and only if the fundamental group of the complement in 3space of the embedding of every subgraph is free. (ii) If two flat embeddings of the same graph are not ambient isotopic, then they differ on a subdivision of $K_5$ or $K_{3,3}$. (iii) Any flat embedding of a graph can be transformed to any other flat embedding of the same graph by ``3switches'', an analog of 2switches from the theory of planar embeddings. In particular, any two flat embeddings of a 4connected graph are either ambient isotopic, or one is ambient isotopic to a mirror image of the other. (iv) A graph has a flat embedding if and only if it has no minor isomorphic to one of seven specified graphs. These are the graphs that can be obtained from $K_6$ by means of $Y\Delta$ and $\Delta Y$exchanges.Is Part Of Bull. Amer. Math. Soc. (N.S.) 28 (1993) 8489 19921231 Identifier ISSN: Category math.CO math.GTLicense 
arXivDifficulties in Inducing a Gauge Theory at Large N B. S. Balakrishna 19921231 It is argued that the recently proposed KazakovMigdal model of induced gauge theory, at large $N$, involves only the zero area Wilson loops that are effectively trees in the gauge action induced by the scalars. This retains only a constant part of the gauge action excluding plaquettes or anything like them and the gauge variables drop out.
Subject Source arXiv URL https://arxiv.org/abs/hepth/9212158view Article Title Difficulties in Inducing a Gauge Theory at Large NAuthors B. S. BalakrishnaAbstract It is argued that the recently proposed KazakovMigdal model of induced gauge theory, at large $N$, involves only the zero area Wilson loops that are effectively trees in the gauge action induced by the scalars. This retains only a constant part of the gauge action excluding plaquettes or anything like them and the gauge variables drop out.Is Part Of Phys.Rev. D49 (1994) 2427 19921231 Identifier ISSN: DOI 10.1103/PhysRevD.49.R24Category hepth heplatLicense