摘要:

We explain how the string spectrum in flat space and pp‐waves arises from the largeNlimit, at fixedgYM2, of U(N)N= 4 super Yang Mills. We reproduce the spectrum by summing a subset of the planar Feynman diagrams. We give a heuristic argument for why we can neglect other diagrams. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1524550

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

The most recent results from the Boomerang, Maxima, DASI, CBI and VSA CMB experiments significantly increase the case for accelerated expansion in the early universe (the inflationary paradigm) and at the current epoch (dark energy dominance). This is especially so when combined with data on high redshift supernovae (SN1) and large scale structure (LSS), encoding information from local cluster abundances, galaxy clustering, and gravitational lensing. There are “7 pillars of Inflation” that can be shown with the CMB probe, and at least 5, and possibly 6, of these have already been demonstrated in the CMB data: (1) the effects of a large scale gravitational potential, demonstrated with COBE/DMR in 1992–96; (2) acoustic peaks/dips in the angular power spectrum of the radiation, which tell about the geometry of the Universe, with the large first peak convincingly shown with Boomerang and Maxima data in 2000, a multiple peak/dip pattern shown in data from Boomerang and DASI (2nd, 3rd peaks, first and 2nd dips in 2001) and from CBI (2nd, 3rd, 4th, 5th peaks, 3rd, 4th dips at 1‐sigma in 2002); (3) damping due to shear viscosity and the width of the region over which hydrogen recombination occurred when the universe was 400000 years old (CBI 2002); (4) the primary anisotropies should have a Gaussian distribution (be maximally random) in almost all inflationary models, the best data on this coming from Boomerang; (5) secondary anisotropies associated with nonlinear phenomena subsequent to 400000 years, which must be there and may have been detected by CBI and another experiment, BIMA. Showing the 5 “pillars” involves detailed confrontation of the experimental data with theory; e.g., (5) compares the CBI data with predictions from two of the largest cosmological hydrodynamics simulations ever done. DASI, Boomerang and CBI in 2002, AMiBA in 2003, and many other experiments have the sensitivity to demonstrate the next pillar, (6) polarization, which must be there at the ∼ 7&percent; level. A broad‐band DASI detection consistent with inflation models was just reported. A 7th pillar, anisotropies induced by gravity wave quantum noise, could be too small to detect. A minimal inflation parameter set, {&ohgr;b, &ohgr;cdm, &OHgr;tot, &OHgr;Q,wQ,ns, &tgr;C, &sgr;8}, is used to illustrate the power of the current data. After marginalizing over the other cosmic and experimental variables, we find the current CMB+LSS+SN1 data give &OHgr;tot=1.00−.03+.07, consistent with (non‐baroque) inflation theory. Restricting to &OHgr;tot= 1, we find a nearly scale invariant spectrum,ns=0.97−.05+.06. The CDM density, &ohgr;cdm= &OHgr;cdmh2=.12−.01+.01, and baryon density, &ohgr;b≡ &OHgr;bh2=.022−.002+.003, are in the expected range. (The Big Bang nucleosynthesis estimate is 0.019 ± 0.002.) Substantial dark (unclustered) energy is inferred, &OHgr;Q≈ 0.68 ± 0.05, and CMB+LSS &OHgr;Qvalues are compatible with the independent SN1 estimates. The dark energy equation of state, crudely parameterized by a quintessence‐field pressure‐to‐density ratiowQ, is not well determined by CMB+LSS (wQ< −0.4 at 95&percent; CL), but when combined with SN1 the resultingwQ< −0.7 limit is quite consistent with thewQ=−1 cosmological constant case. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1524551

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

In TeV‐scale gravity scenarios, the fundamental Planck scale could be as low as a TeV. If so, black hole production should be a prominent feature of scattering experiments at higher energies. Black hole events would have outstanding experimental signatures. The advent of black hole creation also appears to spell the end of our high‐energy exploration of short distance physics, but the beginning of the exploration of extra dimensions of space. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1524552

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

The Sudbury Neutrino Observatory (SNO) is a 1,000 tonne heavy water Cerenkov‐based neutrino detector situated 2,000 meters underground in INCO’s Creighton Mine near Sudbury, Ontario, Canada. For the neutrinos from8B decay in the Sun SNO observes the Charged Current neutrino reaction sensitive only to electron neutrinos and others (Neutral Current and Elastic Scattering) sensitive to all active neutrino types and thereby can search for direct evidence of neutrino flavor change. Using these reactions and assuming the standard8B shape, thevecomponent of the8B solar flux is &fgr;e=1.76−0.05+0.05(stat.)−0.09+0.09(syst.) × 106cm−2s−1for a kinetic energy threshold of 5 MeV. The non‐vecomponent is &fgr;&mgr;&tgr;=3.41−0.45+0.45(stat.)−0.45+0.48(syst.) × 106cm−2s−1, 5.3&sgr; greater than zero, providing strong evidence for solarveflavor transformation. The total flux measured with the NC reaction is &fgr;NC=5.09−0.43+0.44(stat.)−0.43+0.46(syst.) × 106cm−2s−1, consistent with solar models. For charged current events, assuming an undistorted8B spectrum, the night minus day rate is 14.0&percent; ±6.3&percent;−1.4+1.5&percent;of the average rate. If the total flux of active neutrinos is additionally constrained to have no asymmetry, theveasymmetry is found to be 7.0&percent; ±4.9&percent;−1.2+1.3&percent;. A global solar neutrino analysis in terms of matter‐enhanced oscillations of two active flavors strongly favors the Large Mixing Angle (LMA) solution. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1524553

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

The main results of loop quantum gravity, in the connection representation, are summarized, for the case &Lgr; > 0. These include the existence of a ground state, discoverd by Kodama, which both is an exact solution to the constraints of quantum gravity and has a semiclassical limit which is deSitter spacetime. The long wavelength excitations of this state are known to reproduce both gravitons and, when matter is included, quantum field theory on deSitter spacetime. Quantum gravity for &Lgr; > 0 also has an intrinsic thermality, due to the existence of a periodicity on the full configuration space, which generalizes and explains the thermal behavior of quantum fields on deSitter spacetime. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1524554

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

Based on the non‐abelian effective action for D1‐branes, a new action for matrix string theory in non‐trivial backgrounds is proposed. Once the background fields are included, new interactions bring the possibility of non‐commutative solutions i.e. The Myers effect for “string bits”. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1524555

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

A study of the relation between topology change, energy and Lie algebra representations for fuzzy geometry in connection to M‐theory is presented. We encounter two different types of topology change, related to the different features of the Lie algebra representation appearing in the matrix models of M‐theory. From these studies, we propose a new method of obtaining non‐commutative solutions for the non‐Abelian D‐brane action found by Myers. This mechanism excludes one of the two topology changing processes previously found in other non‐commutative solutions of many matrix‐based models in M‐theory i.e. in M(atrix) theory, Matrix string theory and non‐Abelian D‐brane physics. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1524556

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

We investigate a new type of non‐commutative field theory based on a constant skew‐symmetric three‐form parameter. In 3 + 1 dimensions such a three‐form parameter can be viewed as a short‐distance regulator which nevertheless preserves spatial‐rotation and at long range preserves Lorentz invariance approximately. For a scalar field theory with quartic self‐interaction we obtain drastically improved ultra‐violet behavior of the diagrams, due to the oscillatory dependence of the interaction vertex on the momenta. The radiative corrections to the coupling are rendered finite already at the one‐loop level. The key finding of this paper is that what appears as the reemergence of UV divergences as IR singularity inp→ 0 limit, must be interpreted simply as the logarithmic running of the coupling. Thus at low energies the theory is virtually indistinguishable from the standard theory. Conversely at high energies the diagram converges exponentially fast, the running of the coupling stops and the theory avoids developing the Landau pole. Bare coupling defined at high energy can be kept small, and in this sense the theory is similar to asymptotically free theories. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1524557

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

The canonical and symmetrical energy‐momentum tensors and their non‐zero traces in Maxwell’s theory on non‐commutative spaces have been found. Dirac’s quantization of the theory under consideration has been performed. I have found the extended Hamiltonian and equations of motion in the general gauge covariant form. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1524558

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

We consider a reformulation of QED in which covariant Green functions are used to solve for the electromagnetic field in terms of the fermion fields. A simple Fock‐space variational trial state is used to derive relativistic two‐fermion wave equations variationally. We require the trial state to be an eigenstate of the square of the total relativistic angular momentum operator, its projection and parity. It is shown that, in the case of different masses of the particle and the antiparticle, a mixing of single and triplet states takes place. For small coupling constants the fine structure is calculated analytically up to fourth order for all states and mass ratios. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1524559

出版商:AIP    

年代:1902

数据来源: AIP