191 research outputs found
Solar System Experiments and the Interpretation of Saa's Model of Gravity with Propagating Torsion as a Theory with Variable Plank "Constant"
It is shown that the recently proposed interpretation of the transposed
equi-affine theory of gravity as a theory with variable Plank "constant" is
inconsistent with basic solar system gravitational experiments.Comment: 6 pages, latex, no figures. Typos correcte
Global monopoles and scalar fields as the electrogravity dual of Schwarzschild spacetime
We prove that both global monopole and minimally coupled static zero mass
scalar field are electrogravity dual of the Schwarzschild solution or flat
space and they share the same equation of state, . This
property was however known for the global monopole spacetime while it is for
the first time being established for the scalar field. In particular, it turns
out that the Xanthopoulos - Zannias scalar field solution is dual to flat
space.Comment: 5 pages, RevTe
Conformal Black Hole Solutions of Axi-Dilaton Gravity in D-dimensions
Static, spherically symmetric solutions of axi-dilaton gravity in
dimensions is given in the Brans-Dicke frame for arbitrary values of the
Brans-Dicke constant and an axion-dilaton coupling parameter . The
mass and the dilaton and axion charges are determined and a BPS bound is
derived. There exists a one parameter family of black hole solutions in the
scale invariant limit.Comment: 6 PAGES, Rev-tex file, no figures, to appear in Phys-Rev
Matching of analytical and numerical solutions for neutron stars of arbitrary rotation
We demonstrate the results of an attempt to match the two-soliton analytical
solution with the numerically produced solutions of the Einstein field
equations, that describe the spacetime exterior of rotating neutron stars, for
arbitrary rotation. The matching procedure is performed by equating the first
four multipole moments of the analytical solution to the multipole moments of
the numerical one. We then argue that in order to check the effectiveness of
the matching of the analytical with the numerical solution we should compare
the metric components, the radius of the innermost stable circular orbit
(), the rotation frequency and the
epicyclic frequencies . Finally we present some
results of the comparison.Comment: Contribution at the 13th Conference on Recent Developments in Gravity
(NEB XIII), corrected typo in of eq. 5 of the published versio
Conformally dressed black hole in 2+1 dimensions
A three dimensional black hole solution of Einstein equations with negative
cosmological constant coupled to a conformal scalar field is given. The
solution is static, circularly symmetric, asymptotically anti-de Sitter and
nonperturbative in the conformal field. The curvature tensor is singular at the
origin while the scalar field is regular everywhere. The condition that the
Euclidean geometry be regular at the horizon fixes the temperature to be
. Using the Hamiltonian formulation including
boundary terms of the Euclidean action, the entropy is found to be
of the standard value (), and in agreement with
the first law of thermodynamics.Comment: LaTeX ,RevTeX, 13pages, no figure
Stellarator microinstabilities and turbulence at low magnetic shear
[EN] Gyrokinetic simulations of drift waves in low-magnetic-shear stellarators reveal that simulation domains comprised of multiple turns can be required to properly resolve critical mode structures important in saturation dynamics. Marginally stable eigenmodes important in saturation of ion temperature gradient modes and trapped electron modes in the Helically Symmetric Experiment (HSX) stellarator are observed to have two scales, with the envelope scale determined by the properties of the local magnetic shear and an inner scale determined by the interplay between the local shear and magnetic field-line curvature. Properly resolving these modes removes spurious growth rates that arise for extended modes in zero-magnetic-shear approximations, enabling use of a zero-magnetic-shear technique with smaller simulation domains and attendant cost savings. Analysis of subdominant modes in trapped electron mode (TEM)-driven turbulence reveals that the extended marginally stable modes play an important role in the nonlinear dynamics, and suggests that the properties induced by low magnetic shear may be exploited to provide another route for turbulence saturation.The authors would like to thank F. Jenko for insightful questions that motivated this research and J. Smoniewski and J. H. E. Proll for engaging discussions. This work was supported by US DoE grant nos. DE-FG02-99ER54546, DE-FG02-93ER54222 and DE-FG02-89ER53291. J.E.R. was supported by Agencia Estatal de Investigacion (AEI) under grant TIN2016-75985-P, which includes European Commission ERDF funds. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a US Department of Energy Office of Science User Facility operated under contract no. DE-AC02-05CH11231. This research was performed using the compute resources and assistance of the UW-Madison Center For High Throughput Computing (CHTC) in the Department of Computer Sciences. The CHTC is supported by UW-Madison, the Advanced Computing Initiative, the Wisconsin Alumni Research Foundation, the Wisconsin Institutes for Discovery and the National Science Foundation, and is an active member of the Open Science Grid, which is supported by the National Science Foundation and the US Department of Energy's Office of Science.Faber, BJ.; Pueschel, MJ.; Terry, PW.; Hegna, CC.; Roman, JE. (2018). Stellarator microinstabilities and turbulence at low magnetic shear. Journal of Plasma Physics. 84(5). https://doi.org/10.1017/S0022377818001022S845Connor, J. W., & Hastie, R. J. (2004). Microstability in tokamaks with low magnetic shear. Plasma Physics and Controlled Fusion, 46(10), 1501-1535. doi:10.1088/0741-3335/46/10/001Terry, P. W., Faber, B. J., Hegna, C. C., Mirnov, V. V., Pueschel, M. J., & Whelan, G. G. (2018). Saturation scalings of toroidal ion temperature gradient turbulence. Physics of Plasmas, 25(1), 012308. doi:10.1063/1.5007062Hernandez, V., Roman, J. E., & Vidal, V. (2005). SLEPc. ACM Transactions on Mathematical Software, 31(3), 351-362. doi:10.1145/1089014.1089019Friedman, B., Carter, T. A., Umansky, M. V., Schaffner, D., & Joseph, I. (2013). Nonlinear instability in simulations of Large Plasma Device turbulence. Physics of Plasmas, 20(5), 055704. doi:10.1063/1.4805084Eiermann, M., & Ernst, O. G. (2006). A Restarted Krylov Subspace Method for the Evaluation of Matrix Functions. SIAM Journal on Numerical Analysis, 44(6), 2481-2504. doi:10.1137/050633846Connor, J. W., Hastie, R. J., & Taylor, J. B. (1978). Shear, Periodicity, and Plasma Ballooning Modes. Physical Review Letters, 40(6), 396-399. doi:10.1103/physrevlett.40.396Xanthopoulos, P., & Jenko, F. (2007). Gyrokinetic analysis of linear microinstabilities for the stellarator Wendelstein 7-X. Physics of Plasmas, 14(4), 042501. doi:10.1063/1.2714328Hegna, C. C., & Hudson, S. R. (2001). Loss of Second-Ballooning Stability in Three-Dimensional Equilibria. Physical Review Letters, 87(3). doi:10.1103/physrevlett.87.035001Hatch, D. R., Terry, P. W., Jenko, F., Merz, F., Pueschel, M. J., Nevins, W. M., & Wang, E. (2011). Role of subdominant stable modes in plasma microturbulence. Physics of Plasmas, 18(5), 055706. doi:10.1063/1.3563536Faber, B. J., Pueschel, M. J., Proll, J. H. E., Xanthopoulos, P., Terry, P. W., Hegna, C. C., … Talmadge, J. N. (2015). Gyrokinetic studies of trapped electron mode turbulence in the Helically Symmetric eXperiment stellarator. Physics of Plasmas, 22(7), 072305. doi:10.1063/1.4926510Sugama, H., & Watanabe, T.-H. (2006). Collisionless damping of zonal flows in helical systems. Physics of Plasmas, 13(1), 012501. doi:10.1063/1.2149311Hegna, C. C., Terry, P. W., & Faber, B. J. (2018). Theory of ITG turbulent saturation in stellarators: Identifying mechanisms to reduce turbulent transport. Physics of Plasmas, 25(2), 022511. doi:10.1063/1.5018198Zocco, A., Xanthopoulos, P., Doerk, H., Connor, J. W., & Helander, P. (2018). Threshold for the destabilisation of the ion-temperature-gradient mode in magnetically confined toroidal plasmas. Journal of Plasma Physics, 84(1). doi:10.1017/s0022377817000988Merz, F. 2008 Gyrokinetic simulation of multimode plasma turbulence. PhD thesis.Dorland, W., Jenko, F., Kotschenreuther, M., & Rogers, B. N. (2000). Electron Temperature Gradient Turbulence. Physical Review Letters, 85(26), 5579-5582. doi:10.1103/physrevlett.85.5579Xanthopoulos, P., Cooper, W. A., Jenko, F., Turkin, Y., Runov, A., & Geiger, J. (2009). A geometry interface for gyrokinetic microturbulence investigations in toroidal configurations. Physics of Plasmas, 16(8), 082303. doi:10.1063/1.3187907Dinklage, A., Beidler, C. D., Helander, P., Fuchert, G., Maaßberg, H., … Zhang, D. (2018). Magnetic configuration effects on the Wendelstein 7-X stellarator. Nature Physics, 14(8), 855-860. doi:10.1038/s41567-018-0141-9Hatch, D. R., Kotschenreuther, M., Mahajan, S., Valanju, P., Jenko, F., Told, D., … Saarelma, S. (2016). Microtearing turbulence limiting the JET-ILW pedestal. Nuclear Fusion, 56(10), 104003. doi:10.1088/0029-5515/56/10/104003Hatch, D. R., Terry, P. W., Jenko, F., Merz, F., & Nevins, W. M. (2011). Saturation of Gyrokinetic Turbulence through Damped Eigenmodes. Physical Review Letters, 106(11). doi:10.1103/physrevlett.106.115003Proll, J. H. E., Xanthopoulos, P., & Helander, P. (2013). Collisionless microinstabilities in stellarators. II. Numerical simulations. Physics of Plasmas, 20(12), 122506. doi:10.1063/1.4846835Whelan, G. G., Pueschel, M. J., & Terry, P. W. (2018). Nonlinear Electromagnetic Stabilization of Plasma Microturbulence. Physical Review Letters, 120(17). doi:10.1103/physrevlett.120.175002Friedman, B., & Carter, T. A. (2014). Linear Technique to Understand Non-Normal Turbulence Applied to a Magnetized Plasma. Physical Review Letters, 113(2). doi:10.1103/physrevlett.113.025003High mode number stability of an axisymmetric toroidal plasma. (1979). Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences, 365(1720), 1-17. doi:10.1098/rspa.1979.0001Boozer, A. H. (1998). What is a stellarator? Physics of Plasmas, 5(5), 1647-1655. doi:10.1063/1.872833Boozer, A. H. (1981). Plasma equilibrium with rational magnetic surfaces. Physics of Fluids, 24(11), 1999. doi:10.1063/1.863297Dewar, R. L. (1983). Ballooning mode spectrum in general toroidal systems. Physics of Fluids, 26(10), 3038. doi:10.1063/1.864028Anderson, F. S. B., Almagri, A. F., Anderson, D. T., Matthews, P. G., Talmadge, J. N., & Shohet, J. L. (1995). The Helically Symmetric Experiment, (HSX) Goals, Design and Status. Fusion Technology, 27(3T), 273-277. doi:10.13182/fst95-a11947086Bhattacharjee, A. (1983). Drift waves in a straight stellarator. Physics of Fluids, 26(4), 880. doi:10.1063/1.864229Baumgaertel, J. A., Belli, E. A., Dorland, W., Guttenfelder, W., Hammett, G. W., Mikkelsen, D. R., … Xanthopoulos, P. (2011). Simulating gyrokinetic microinstabilities in stellarator geometry with GS2. Physics of Plasmas, 18(12), 122301. doi:10.1063/1.3662064Blackford, L. S., Choi, J., Cleary, A., D’Azevedo, E., Demmel, J., Dhillon, I., … Whaley, R. C. (1997). ScaLAPACK Users’ Guide. doi:10.1137/1.9780898719642Martin, M. F., Landreman, M., Xanthopoulos, P., Mandell, N. R., & Dorland, W. (2018). The parallel boundary condition for turbulence simulations in low magnetic shear devices. Plasma Physics and Controlled Fusion, 60(9), 095008. doi:10.1088/1361-6587/aad38aPlunk, G. G., Xanthopoulos, P., & Helander, P. (2017). Distinct Turbulence Saturation Regimes in Stellarators. Physical Review Letters, 118(10). doi:10.1103/physrevlett.118.105002Candy, J., Waltz, R. E., & Rosenbluth, M. N. (2004). Smoothness of turbulent transport across a minimum-q surface. Physics of Plasmas, 11(5), 1879-1890. doi:10.1063/1.1689967Nagaoka, K., Takahashi, H., Murakami, S., Nakano, H., Takeiri, Y., Tsuchiya, H., … Komori, A. (2015). Integrated discharge scenario for high-temperature helical plasma in LHD. Nuclear Fusion, 55(11), 113020. doi:10.1088/0029-5515/55/11/113020Canik, J. M., Anderson, D. T., Anderson, F. S. B., Likin, K. M., Talmadge, J. N., & Zhai, K. (2007). Experimental Demonstration of Improved Neoclassical Transport with Quasihelical Symmetry. Physical Review Letters, 98(8). doi:10.1103/physrevlett.98.085002Dimits, A. M., Williams, T. J., Byers, J. A., & Cohen, B. I. (1996). Scalings of Ion-Temperature-Gradient-Driven Anomalous Transport in Tokamaks. Physical Review Letters, 77(1), 71-74. doi:10.1103/physrevlett.77.71Beer, M. A., Cowley, S. C., & Hammett, G. W. (1995). Field‐aligned coordinates for nonlinear simulations of tokamak turbulence. Physics of Plasmas, 2(7), 2687-2700. doi:10.1063/1.871232Gates, D. A., Anderson, D., Anderson, S., Zarnstorff, M., Spong, D. A., Weitzner, H., … Glasser, A. H. (2018). Stellarator Research Opportunities: A Report of the National Stellarator Coordinating Committee. Journal of Fusion Energy, 37(1), 51-94. doi:10.1007/s10894-018-0152-7Helander, P. (2014). Theory of plasma confinement in non-axisymmetric magnetic fields. Reports on Progress in Physics, 77(8), 087001. doi:10.1088/0034-4885/77/8/087001Peeters, A. G., Camenen, Y., Casson, F. J., Hornsby, W. A., Snodin, A. P., Strintzi, D., & Szepesi, G. (2009). The nonlinear gyro-kinetic flux tube code GKW. Computer Physics Communications, 180(12), 2650-2672. doi:10.1016/j.cpc.2009.07.001Jenko, F., Dorland, W., Kotschenreuther, M., & Rogers, B. N. (2000). Electron temperature gradient driven turbulence. 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Physics of Plasmas, 20(9), 092511. doi:10.1063/1.482198
Collisions of Einstein-Conformal Scalar Waves
A large class of solutions of the Einstein-conformal scalar equations in
D=2+1 and D=3+1 is identified. They describe the collisions of asymptotic
conformal scalar waves and are generated from Einstein-minimally coupled scalar
spacetimes via a (generalized) Bekenstein transformation. Particular emphasis
is given to the study of the global properties and the singularity structure of
the obtained solutions. It is shown, that in the case of the absence of pure
gravitational radiation in the initial data, the formation of the final
singularity is not only generic, but is even inevitable.Comment: 17 pages, LaTe
No Scalar Hair Theorem for a Charged Spherical Black Hole
This paper consolidates noscalar hair theorem for a charged spherically
symmetric black hole in four dimension in general relativity as well as in all
scalar tensor theories, both minimally and nonminimally coupled, when the
effective Newtonian constant of gravity is positive. However, there is an
exception when the matter field itself is coupled to the scalar field, such as
in dilaton gravity.Comment: 13 pages, Latex format, some minor corrections are made, accepted for
publication in Physical Review
Kerr-Schild Symmetries
We study continuous groups of generalized Kerr-Schild transformations and the
vector fields that generate them in any n-dimensional manifold with a
Lorentzian metric. We prove that all these vector fields can be intrinsically
characterized and that they constitute a Lie algebra if the null deformation
direction is fixed. The properties of these Lie algebras are briefly analyzed
and we show that they are generically finite-dimensional but that they may have
infinite dimension in some relevant situations. The most general vector fields
of the above type are explicitly constructed for the following cases: any
two-dimensional metric, the general spherically symmetric metric and
deformation direction, and the flat metric with parallel or cylindrical
deformation directions.Comment: 15 pages, no figures, LaTe
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