Showing 2901 - 2950 of 5831 Items
Date: 2003-01-01
Creator: T.W. Baumgarte, S.L. Shapiro
Access: Open access
Date: 2002-01-01
Creator: Kenneth A. Dennison, William K. Wootters
Access: Open access
- The entanglement sharing among quantum particles was discussed in a system consisting of n d-dimensional quantum particles. The entanglement between each pair was attempted to get optimized. A three particles system was also considered and results showed that the particles shared a greater fraction of their entanglement capacity as the dimension d increased.
Date: 2001-07-01
Creator: Jeffrey P. Severinghaus, Alexi Grachev, Mark Battle
Access: Open access
- Air withdrawn from the top 5-15 m of the polar snowpack (firn) shows anomalous enrichment of heavy gases during summer, including inert gases. Following earlier work, we ascribe this to thermal diffusion, the tendency of a gas mixture to separate in a temperature gradient, with heavier molecules migrating toward colder regions. Summer warmth creates a temperature gradient in the top few meters of the firn due to the thermal inertia of the underlying firn and causes gas fractionation by thermal diffusion. Here we explore and quantify this process further in order to (1) correct for bias caused by thermal diffusion in firn air and ice core air isotope records, (2) help calibrate a new technique for measuring temperature change in ice core gas records based on thermal diffusion [Severinghaus et al., 1998], and (3) address whether air in polar snow convects during winter and, if so, whether it creates a rectification of seasonality that could bias the ice core record. We sampled air at 2-m-depth intervals from the top 15 m of the firn at two Antarctic sites, Siple Dome and South Pole, including a winter sampling at the pole. We analyzed 15N/14N, 40Ar/36Ar, 40Ar/38Ar, 18O/16O of O2, O2/N2, 84Kr/36Ar, and 132Xe/36Ar. The results show the expected pattern of fractionation and match a gas diffusion model based on first principles to within 30%. Although absolute values of thermal diffusion sensitivities cannot be determined from the data with precision, relative values of different gas pairs may. At Siple Dome, δ40Ar/4 is 66 ± 2% as sensitive to thermal diffusion as δ15N, in agreement with laboratory calibration; δ18O/2 is 83 ± 3%, and δ84Kr/48 is 33 ± 3% as sensitive as δ15N. The corresponding figures for summer South Pole are 64 ± 2%, 81 ± 3%, and 34 ± 3%. Accounting for atmospheric change, the figure for δO2/N2/4 is 90 ± 3% at Siple Dome. Winter South Pole shows a strong depletion of heavy gases as expected. However, the data do not fit the model well in the deeper part of the profile and yield a systematic drift with depth in relative thermal diffusion sensitivities (except for Kr, constant at 34 ± 4%), suggesting the action of some other process that is not currently understood. No evidence for wintertime convection or a rectifier effect is seen.
Date: 2007-12-24
Creator: Stephen G. Naculich, Benjamin H. Ripman
Access: Open access
- We analyze the level-rank duality of untwisted and ε-twisted D-branes of the over(so, ̂) (N)K WZW model. Untwisted D-branes of over(so, ̂) (N)K are characterized by integrable tensor and spinor representations of over(so, ̂) (N)K. Level-rank duality maps untwisted over(so, ̂) (N)K D-branes corresponding to (equivalence classes of ) tensor representations onto those of over(so, ̂) (K)N. The ε-twisted D-branes of over(so, ̂) (2 n)2 k are characterized by (a subset of ) integrable tensor and spinor representations of over(so, ̂) (2 n - 1)2 k + 1. Level-rank duality maps spinor ε-twisted over(so, ̂) (2 n)2 k D-branes onto those of over(so, ̂) (2 k)2 n. For both untwisted and ε-twisted D-branes, we prove that the spectrum of an open string ending on these D-branes is isomorphic to the spectrum of an open string ending on the level-rank-dual D-branes. © 2007 Elsevier B.V. All rights reserved.
Date: 2013-04-19
Creator: Stephen G. Naculich, Horatiu Nastase, Howard J. Schnitzer
Access: Open access
- The infrared singularities of gravitational amplitudes are one-loop exact, in that higher-loop divergences are characterized by the exponential of the one-loop divergence. We show that the contributions to SU(N) gauge-theory amplitudes that are mostsubleading in the 1/N expansion are also one-loop exact, provided that the dipole conjecture holds. Possible corrections to the dipole conjecture, beginning at three loops, could violate one-loop-exactness, though would still maintain the absence of collinear divergences. We also demonstrate a relation between L-loop four-point N = 8 supergravity and mostsubleading-color N = 4 SYM amplitudes that holds for the two leading IR divergences, (Formula presented.) and (Formula presented.), but breaks down at (Formula presented.).
Date: 2010-01-01
Creator: S. A. Montzka, L. Kuijpers, M. O. Battle, M. Aydin, K. R., Verhulst, E. S. Saltzman, D. W. Fahey
Access: Open access
- Firn-air and ambient air measurements of CHF3 (HFC- 23) from three excursions to Antarctica between 2001 and 2009 are used to construct a consistent Southern Hemisphere (SH) atmospheric history. The results show atmospheric mixing ratios of HFC-23 continuing to increase through 2008. Mean global emissions derived from this data for 2006-2008 are 13.5 ± 2 Gg/yr (200 ± 30 × 1012gCO2- equivalent/yr, or MtCO2-eq./yr), ∼50% higher than the 8.7 ± 1 Gg/yr (130 ± 15 MtCO2-eq./yr) derived for the 1990s. HFC-23 emissions arise primarily from over-fluorination of chloroform during HCFC-22 production. The recent global emission increases are attributed to rapidly increasing HCFC-22 production in developing countries since reported HFC-23 emissions from developed countries decreased over this period. The emissions inferred here for developing countries during 2006-2008 averaged 11 ± 2 Gg/yr HFC-23 (160 ± 30 MtCO2-eq./yr) and are larger than the ∼6 Gg/yr of HFC-23 destroyed in United Nations Framework Convention on Climate Change Clean Development Mechanism projects during 2007 and 2008. © Copyright 2010 by the American Geophysical Union.
Date: 2003-12-08
Creator: Stephen G. Naculich, Howard J. Schnitzer, Niclas Wyllard
Access: Open access
- Using matrix-model methods we study three different N=2 models: U(N)×U(N) with matter in the bifundamental representation, U(N) with matter in the symmetric representation, and U(N) with matter in the antisymmetric representation. We find that the (singular) cubic Seiberg-Witten curves (and associated Seiberg-Witten differentials) implied by the matrix models, although of a different form from the ones previously proposed using M-theory, can be transformed into the latter and are thus physically equivalent. We also calculate the one-instanton corrections to the gauge-coupling matrix using the perturbative expansion of the matrix model. For the U(N) theories with symmetric or antisymmetric matter we use the modified matrix-model prescription for the gauge-coupling matrix discussed in our paper: Cubic curves from matrix models and generalized Konishi anomalies (hep-th/0303268). Moreover, in the matrix model for the U(N) theory with antisymmetric matter, one is required to expand around a different vacuum than one would naively have anticipated. With these modifications of the matrix-model prescription, the results of this paper are in complete agreement with those of Seiberg-Witten theory obtained using M-theory methods. © 2003 Elsevier B.V. All rights reserved.
Date: 2007-03-13
Creator: Thomas W. Baumgarte, Stephen G. Naculich
Access: Open access
- The "moving-puncture" technique has led to dramatic advancements in the numerical simulations of binary black holes. Hannam et al. have recently demonstrated that, for suitable gauge conditions commonly employed in moving-puncture simulations, the evolution of a single black hole leads to a well-known, time-independent, maximal slicing of Schwarzschild spacetime. They construct the corresponding solution in isotropic coordinates numerically and demonstrate its usefulness, for example, for testing and calibrating numerical codes that employ moving-puncture techniques. In this brief report we point out that this solution can also be constructed analytically, making it even more useful as a test case for numerical codes. © 2007 The American Physical Society.
Date: 1994-01-01
Creator: R. Balest, K. Cho, M. Daoudi, W. T. Ford, D. R., Johnson, K. Lingel, M. Lohner, P. Rankin, J. G. Smith, J. P. Alexander, C. Bebek, K. Berkelman, K. Bloom, T. E. Browder, D. G. Cassel, H. A. Cho, D. M. Coffman, P. S. Drell, R. Ehrlich, P. Gaiderev, M. Garcia-Sciveres, B. Geiser, B. Gittelman, S. W. Gray, D. L. Hartill, B. K. Heltsley, C. D. Jones, S. L. Jones, J. Kandaswamy, N. Katayama, P. C. Kim
Access: Open access
- Using the CLEO II detector at the Cornell Electron Storage Ring we have measured the ratio of branching fractions, B(D+K-++)/(D0K-+)=2.350.160.16. Our recent measurement of scrB(D0K-+) then gives scrB(D+K-++)=(9.30.60.8)%. © 1994 The American Physical Society.
Date: 1993-12-01
Creator: D. S. Akerib, B. Barish, M. Chadha, D. F. Cowen, G., Eigen, J. S. Miller, J. Urheim, A. J. Weinstein, D. Acosta, G. Masek, B. Ong, H. Paar, M. Sivertz, A. Bean, J. Gronberg, R. Kutschke, S. Menary, R. J. Morrison, H. N. Nelson, J. D. Richman, H. Tajima, D. Schmidt, D. Sperka, M. S. Witherell, M. Procario, S. Yang, M. Daoudi, W. T. Ford, D. R. Johnson, K. Lingel, M. Lohner
Access: Open access
Date: 2005-07-01
Creator: Marta Gómez-Reino, Stephen G. Naculich, Howard J. Schnitzer
Access: Open access
- We extend the methods of Spradlin and Volovich to compute the partition function for a conformally-invariant gauge theory on ℝ × S 3 in which the dilatation operator is represented by a spin-chain hamiltonian acting on pairs of states, not necessarily nearest neighbors. A specific application of this is the two-loop dilatation operator of the planar SU(2) subsector of the N ≤ 4 SU(N) super Yang-Mills theory in the large-N limit. We compute the partition function and Hagedorn temperature for this sector to second order in the gauge coupling. The Hagedorn temperature is to be interpreted as giving the exponentially-rising portion of the density of states of the SU(2) sector, which may be a signal of stringy behavior in the dual theory. © SISSA 2005.
Date: 1995-01-01
Creator: R. Balest, K. Cho, W. T. Ford, D. R. Johnson, K., Lingel, M. Lohner, P. Rankin, J. G. Smith, J. P. Alexander, C. Bebek, K. Berkelman, K. Bloom, T. E. Browder, D. G. Cassel, H. A. Cho, D. M. Coffman, D. S. Crowcroft, P. S. Drell, D. J. Dumas, R. Ehrlich, P. Gaidarev, M. Garcia-Sciveres, B. Geiser, B. Gittelman, S. W. Gray, D. L. Hartill, B. K. Heltsley, S. Henderson, C. D. Jones, S. L. Jones, J. Kandaswamy
Access: Open access
- We have used the CLEO-II detector at the Cornell Electron Storage Ringe (CESR) to study the inclusive production of charmonium mesons in a sample of 2.15 million BB events. We find inclusive branching fractions of (1.120.040.06)% for BJ/X, (0.340.040.03)% for BX, and (0.400.060.04)% for Bc1X. We also find some evidence for the inclusive production of c2, and set an upper limit for the branching fraction of the inclusive decay BcX of 0.9% at 90% confidence level. Momentum spectra for inclusive J/, and c1 production are presented. These measurements are compared to theoretical calculations. © 1995 The American Physical Society.
Date: 1995-01-01
Creator: B. Barish, M. Chadha, S. Chan, D. F. Cowen, G., Eigen, J. S. Miller, C. O'Grady, J. Urheim, A. J. Weinstein, D. Acosta, M. Athanas, G. Masek, H. P. Paar, J. Gronberg, R. Kutschke, S. Menary, R. J. Morrison, S. Nakanishi, H. N. Nelson, T. K. Nelson, C. Qiao, J. D. Richman, A. Ryd, H. Tajima, D. Sperka, M. S. Witherell, M. Procario, R. Balest, K. Cho, M. Daoudi, W. T. Ford
Access: Open access
- We study the exclusive semileptonic B meson decays B-→D*0l-ν̄ and B̄0→D*+l-ν̄ using data collected with the CLEO II detector at the Cornell Electron-positron Storage Ring (CESR). We present measurements of the branching fractions scrB(B̄0→D*+l-ν̄)= (0.5/f00)[4.49±0.32(stat.)±0.39 (syst.)]% and scrB(B-→D*0l-(ν̄)= (0.5/f+-)[5.13±0.54 (stat) ±0.64 (syst)]%, where f00 and f+- are the neutral and charged B meson production fractions at the Υ(4S) resonance, respectively. Assuming isospin invariance and taking the ratio of charged to neutral B meson lifetimes measured at higher energy machines, we determine the ratio f+-/f00=1.04±0.13 (stat) ±0.12 (syst) ±0.10 (lifetime); further assuming f+-+f00=1 we also determine the partial width Γ(B̄→D*lν̄)=[29.9±1.9 (stat) ±2.7 (syst.) ±2.0 (lifetime)] ns-1 (independent of f+-/f00). From this partial width we calculate B̄→D*lν̄ branching fractions that do not depend on f+-/f00 or the individual B lifetimes, but only on the charged to neutral B lifetime ratio. The product of the CKM matrix element -Vcb- times the normalization of the decay form factor at the point of no recoil of the D* meson, scrF(y=1), is determined from a linear fit to the combined differential decay rate of the exclusive B̄→D*lν̄ decays: -Vcb-scrF(1)=0.0351±0.0019 (stat) ±0.0018 (syst) ±0.0008 (lifetime). The value for -Vcb- is extracted using theoretical calculations of the form factor normalization. © 1995 The American Physical Society.
Date: 1994-12-01
Creator: D. Cinabro, T. Liu, M. Saulnier, R. Wilson, H., Yamamoto, T. Bergfeld, B. I. Eisenstein, G. Gollin, B. Ong, M. Palmer, M. Selen, J. J. Thaler, K. W. Edwards, M. Ogg, A. Bellerive, D. I. Britton, E. R.F. Hyatt, D. B. MacFarlane, P. M. Patel, B. Spaan, A. J. Sadoff, R. Ammar, P. Baringer, A. Bean, D. Besson, D. Coppage, N. Copty, R. Davis, N. Hancock, M. Kelly, S. Kotov
Access: Open access
- We have studied the leptonic decay of the γ (1S) resonance into tau pairs using the CLEO II detector. A clean sample of tau pair events is identified via events containing two charged particles where exactly one of the particles is an identified electron. We find B(γ(1S) → τ+τ-) = (2.61±0.12-0.13+0.09)%. The result is consistent with expectations from lepton universality. © 1994.
Date: 2014-09-16
Creator: M. O. Battle, J. P. Severinghaus, E. D. Sofen, D. Plotkin, A. J., Orsi, M. Aydin, S. A. Montzka, T. Sowers, P. P. Tans
Access: Open access