scholarly journals All massless, scalar fields with trivialS-matrix are wick-polynomials

1982 ◽  
Vol 86 (2) ◽  
pp. 247-256 ◽  
Author(s):  
Klaus Baumann
Keyword(s):  
Scalar Fields ◽  
Massless Scalar

scholarly journals Failure of mean-field approximation in weakly coupled dilaton gravity

2018 ◽  
Vol 191 ◽  
pp. 07004
Author(s):  
Maxim Fitkevich
Keyword(s):  
Black Hole ◽  
Mean Field ◽  
Direct Calculation ◽  
Scalar Fields ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Massless Scalar ◽  
Dilaton Gravity ◽  
Black Hole Evaporation ◽  
Weakly Coupled

We investigate black hole evaporation in a weakly coupled model of two-dimensional dilaton gravity paying a particular attention to the validity of the semiclassical mean-field approximation. Our model is obtained by adding a reflecting boundary to the celebrated RST model describing N gravitating massless scalar fields to one-loop level. The boundary cuts off the region of strong coupling. Although our model is explicitly weakly coupled, we find that the mean field approximation inevitably fails at the end of black hole evaporation. We propose an alternative semiclassical method aiming at direct calculation of S-matrix elements and illustrate it in a simple shell model.

On the vacuum stress induced by uniform acceleration or supporting the ether

1977 ◽  
Vol 354 (1676) ◽  
pp. 79-99 ◽  
Keyword(s):  
Scalar Field ◽  
Boundary Conditions ◽  
Neumann Boundary ◽  
Scalar Fields ◽  
Black Body ◽  
Dirichlet Boundary Conditions ◽  
Massless Scalar ◽  
Perfect Conductor ◽  
Infinite Plane ◽  
Uniform Acceleration

The stresses induced in the vacuum by the uniform acceleration of an infinite plane conductor are computed for the massless scalar and electromagnetic fields. Both Dirichlet and Neumann boundary conditions are considered for the scalar field; far from the conductor it is found, independently of the boundary condition, that the vacuum stress is ‘local’ and corresponds to the absence from the vacuum of black body radiation. Approaching the conductor, the energy density in the Dirichlet case is slightly lower than the ‘local’ term, and in the Neumann case slightly higher. At very small distances it again has the same asymptotic form for both scalar fields. For the electromagnetic field the results are similar to those for the scalar field with Dirichlet boundary conditions. Far from the conductor the spectrum is again black-body, though not Planckian. In all cases the acausal nature of ‘ perfect conductor ’ boundary conditions prevents the stress tensor from being finite on the conductor.

scholarly journals Pseudo-topological transitions in 2D gravity models coupled to massless scalar fields

2012 ◽  
Vol 863 (2) ◽  
pp. 421-434 ◽  
Author(s):  
J. Ambjørn ◽  
A.T. Görlich ◽  
J. Jurkiewicz ◽  
H.-G. Zhang
Keyword(s):  
2D Gravity ◽  
Scalar Fields ◽  
Gravity Models ◽  
Massless Scalar ◽  
Topological Transitions

scholarly journals PASSAGE OF RADIATION THROUGH WORMHOLES

2009 ◽  
Vol 18 (11) ◽  
pp. 1665-1691 ◽  
Author(s):  
ANDREY DOROSHKEVICH ◽  
JAKOB HANSEN ◽  
IGOR NOVIKOV ◽  
ALEXANDER SHATSKIY
Keyword(s):  
Black Hole ◽  
Scalar Fields ◽  
Radiation Pulse ◽  
Massless Scalar ◽  
Subsequent Evolution ◽  
Gravitational Action ◽  
Zero Mass ◽  
Symmetrical Solution

We investigate numerically the process of the passage of a radiation pulse through a wormhole and the subsequent evolution of the wormhole that is caused by the gravitational action of this pulse. The initial static wormhole is modeled by a spherically symmetrical solution with zero mass. The radiation pulses are modeled by spherically symmetrical shells of self-gravitating massless scalar fields. We demonstrate that the compact signal propagates through the wormhole and investigate the dynamics of the fields in this process for both cases: collapse of the wormhole into the black hole and for the expanding wormhole.

scholarly journals Massless scalar fields and topological black holes

2000 ◽  
Vol 61 (8) ◽  
Author(s):  
Tekin Dereli ◽  
Yuri N. Obukhov
Keyword(s):  
Black Holes ◽  
Scalar Fields ◽  
Massless Scalar

Stationary bound states of massless scalar fields around black holes and black hole analogues

2015 ◽  
Vol 24 (09) ◽  
pp. 1542018 ◽  
Author(s):  
Carolina L. Benone ◽  
Luís C. B. Crispino ◽  
Carlos A. R. Herdeiro ◽  
Eugen Radu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Spatial Distribution ◽  
Scalar Field ◽  
Bound States ◽  
Neumann Boundary ◽  
Mass Term ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Field System

We discuss stationary bound states, a.k.a. clouds, for a massless test scalar field around Kerr black holes (BHs) and spinning acoustic BH analogues. In view of the absence of a mass term, the trapping is achieved via enclosing the BH — scalar field system in a cavity and imposing Dirichlet or Neumann boundary conditions. We discuss the variation of these bounds states with the discrete parameters that label them, as well as their spatial distribution, complementing results in our previous work [C. L. Benone, L. C. B. Crispino, C. Herdeiro and E. Radu, Phys. Rev. D91 (2015) 104038].

Absorption of zero-mass planar waves by dirty black holes

2018 ◽  
Vol 27 (11) ◽  
pp. 1843017 ◽  
Author(s):  
Caio F. B. Macedo ◽  
Luiz C. S. Leite ◽  
Luís C. B. Crispino
Keyword(s):  
Black Holes ◽  
Cross Section ◽  
Accretion Disks ◽  
Absorption Cross Section ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Absorption Cross ◽  
Thin Spherical Shell ◽  
Nonlinear Nature ◽  
Selection Of

Astrophysical black holes are often with companions, including other gravitating objects, accretion disks, electromagnetic fields, and others. Because of the nonlinear nature of general relativity, it is difficult to account for the gravitational effects of these companions, which can only be investigated analytically for very few cases. In this paper, we consider black holes with surrounding matter — often called dirty black holes — and analyze the absorption cross section of massless scalar fields. We start by laying out the generic setup for spherically symmetric scenarios and then specify for a simple model. We consider planar massless scalar waves impinging upon a Schwarzschild black hole surrounded by a thin spherical shell, and compute the absorption cross section. We present a selection of numerical results complementary to those presented in [C. F. B. Macedo, L. C. S. Leite and L. C. B. Crispino, Phys. Rev. D 93 (2016) 024027, arXiv:1511.08781 [gr-qc]] for arbitrary frequencies, considering different values of the shell position as well as its mass.

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