Nonlinear electrodynamics nonminimally coupled to gravity: Symmetric-hyperbolicity and causal structure

In this paper, we propose a n-dimensional action in which gravity is coupled to exponential nonlinear electrodynamics and scalar dilaton field with Liouville-type potential. By varying the action, we obtain the field equations. Then, we construct a new class of charged, rotating black brane solutions, with k = [(n – 1)/2] rotation parameters, of this theory. Because of the presence of the Liouville-type dilaton potential, the asymptotic behavior of the obtained solutions is neither flat nor (anti)-de Sitter. We investigate the causal structure of the space–time in ample details. We find the suitable counter term that removes the divergences of the action in the presence of the dilaton field, and calculate the conserved and thermodynamic quantities of the space–time. Interestingly enough, we find that the conserved quantities crucially depend on the dilaton coupling constant, α, while they are independent of the nonlinear parameter, β. We also check the validity of the first law of thermodynamics on the black brane horizon. Finally, we study thermal stability of the solutions by computing the heat capacity in the canonical ensemble. We disclose the effects of rotation parameter, nonlinearity of electrodynamics, and dilaton field on the thermal stability conditions.

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Causal structure and birefringence in nonlinear electrodynamics

Modern Physics Letters A ◽

10.1142/s021773231550025x ◽

2015 ◽

Vol 30 (06) ◽

pp. 1550025 ◽

Cited By ~ 7

Author(s):

C. A. M. de Melo ◽

L. G. Medeiros ◽

P. J. Pompeia

Keyword(s):

Causal Structure ◽

Nonlinear Electrodynamics ◽

Effective Metric

We investigate the causal structure of general nonlinear electrodynamics and determine which Lagrangians generate an effective metric conformal to Minkowski. We also prove that there is only one analytic nonlinear electrodynamics not presenting birefringence.

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SCALAR–TENSOR BLACK HOLES COUPLED TO EULER–HEISENBERG NONLINEAR ELECTRODYNAMICS

Modern Physics Letters A ◽

10.1142/s0217732307023560 ◽

2007 ◽

Vol 22 (17) ◽

pp. 1217-1231 ◽

Cited By ~ 28

Author(s):

IVAN ZH. STEFANOV ◽

STOYTCHO S. YAZADJIEV ◽

MICHAIL D. TODOROV

Keyword(s):

Black Holes ◽

Scalar Field ◽

Numerical Solutions ◽

Causal Structure ◽

Nonlinear Electrodynamics ◽

Massless Scalar ◽

Massless Scalar Field ◽

Charged Black Holes ◽

Maxwell Electrodynamics ◽

Scalar Hair

The no-scalar-hair conjecture rules out the existence of asymptotically flat black holes with a scalar dressing for a large class of theories. No-scalar-hair theorems have been proved for the cases of neutral black holes and for charged black holes in the Maxwell electrodynamics. These theorems, however, do not apply in the case of nonlinear electrodynamics. In the present work numerical solutions describing charged black holes coupled to Euler–Heisenberg type nonlinear electrodynamics in scalar–tensor theories of gravity with massless scalar field are found. In comparison to the corresponding solution in General Relativity the presented solution has a simpler causal structure the reason for which is the presence of the scalar field. The present class of black holes has a single, nondegenerate horizon, i.e. its causal structure resembles that of the Schwarzschild black hole.

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PHASES OF 4D SCALAR–TENSOR BLACK HOLES COUPLED TO BORN–INFELD NONLINEAR ELECTRODYNAMICS

Modern Physics Letters A ◽

10.1142/s0217732308028351 ◽

2008 ◽

Vol 23 (34) ◽

pp. 2915-2931 ◽

Cited By ~ 54

Author(s):

IVAN ZH. STEFANOV ◽

STOYTCHO S. YAZADJIEV ◽

MICHAIL D. TODOROV

Keyword(s):

Black Holes ◽

Scalar Field ◽

Numerical Solutions ◽

Causal Structure ◽

Nonlinear Electrodynamics ◽

Schwarzschild Black Hole ◽

Charged Black Holes ◽

Maxwell Electrodynamics ◽

Scalar Hair ◽

The Stability

Recent results show that when nonlinear electrodynamics is considered, the no-scalar-hair theorems in the scalar–tensor theories (STT) of gravity, which are valid for the cases of neutral black holes and charged black holes in the Maxwell electrodynamics, can be circumvented.1,2 What is even more, in the present work, we find new non-unique, numerical solutions describing charged black holes coupled to nonlinear electrodynamics in a special class of scalar–tensor theories. One of the phases has a trivial scalar field and coincides with the corresponding solution in General Relativity. The other phases that we find are characterized by the value of the scalar field charge. The causal structure and some aspects of the stability of the solutions have also been studied. For the scalar–tensor theories considered, the black holes have a single, non-degenerate horizon, i.e. their causal structure resembles that of the Schwarzschild black hole. The thermodynamic analysis of the stability of the solutions indicates that a phase transition may occur.

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Asymptotically (A)dS dilaton black holes with nonlinear electrodynamics

International Journal of Modern Physics D ◽

10.1142/s021827181850075x ◽

2018 ◽

Vol 27 (07) ◽

pp. 1850075 ◽

Cited By ~ 5

Author(s):

S. Hajkhalili ◽

A. Sheykhi

Keyword(s):

Black Holes ◽

Electric Field ◽

Gauge Field ◽

Causal Structure ◽

Nonlinear Electrodynamics ◽

Thermodynamic Quantities ◽

Dilaton Field ◽

Maximum Value ◽

Nonlinear Gauge ◽

Dilaton Black Holes

It is well known that with an appropriate combination of three Liouville-type dilaton potentials, one can construct charged dilaton black holes in an (anti)-de Sitter [(A)dS] spaces in the presence of linear Maxwell field. However, asymptotically (A)dS dilaton black holes coupled to nonlinear gauge field have not been found. In this paper, we construct, for the first time, three new classes of dilaton black hole solutions in the presence of three types of nonlinear electrodynamics, namely Born–Infeld (BI), Logarithmic (LN) and Exponential nonlinear (EN) electrodynamics. All these solutions are asymptotically (A)dS and in the linear regime reduce to the Einstein–Maxwell-dilaton (EMd) black holes in (A)dS spaces. We investigate physical properties and the causal structure, as well as asymptotic behavior of the obtained solutions, and show that depending on the values of the metric parameters, the singularity can be covered by various horizons. We also calculate conserved and thermodynamic quantities of the obtained solutions. Interestingly enough, we find that the coupling of dilaton field and nonlinear gauge field in the background of (A)dS spaces leads to a strange behavior for the electric field. We observe that the electric field is zero at singularity and increases smoothly until reaches a maximum value, then it decreases smoothly until goes to zero as [Formula: see text]. The maximum value of the electric field increases with increasing the nonlinear parameter [Formula: see text] or decreasing the dilaton coupling [Formula: see text] and is shifted to the singularity in the absence of either dilaton field ([Formula: see text]) or nonlinear gauge field ([Formula: see text]).

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Special, radical, failure of reduction in psychiatry

Behavioral and Brain Sciences ◽

10.1017/s0140525x18001164 ◽

2019 ◽

Vol 42 ◽

Author(s):

Don Ross

Keyword(s):

Mental Disorder ◽

Brain Structure ◽

Causal Structure ◽

Network Models ◽

Gambling Addiction ◽

Brain Disorder ◽

Mental Processes ◽

Special Radical ◽

Intentional Relationships

AbstractUse of network models to identify causal structure typically blocks reduction across the sciences. Entanglement of mental processes with environmental and intentional relationships, as Borsboom et al. argue, makes reduction of psychology to neuroscience particularly implausible. However, in psychiatry, a mental disorder can involve no brain disorder at all, even when the former crucially depends on aspects of brain structure. Gambling addiction constitutes an example.

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Blocking Is Sensitive to Causal Structure in 4-Year-Old and 8-Year-Old Children

Experimental Psychology (formerly Zeitschrift für Experimentelle Psychologie) ◽

10.1027/1618-3169.52.4.264 ◽

2005 ◽

Vol 52 (4) ◽

pp. 264-271 ◽

Cited By ~ 4

Author(s):

Tom Beckers ◽

Uschi Van den Broeck ◽

Marij Renne ◽

Stefaan Vandorpe ◽

Jan De Houwer ◽

...

Keyword(s):

Young Children ◽

Associative Learning ◽

Learning Theory ◽

Causal Structure ◽

Age Groups ◽

Learning Task ◽

Contingency Learning

Abstract. In a contingency learning task, 4-year-old and 8-year-old children had to predict the outcome displayed on the back of a card on the basis of cues presented on the front. The task was embedded in either a causal or a merely predictive scenario. Within this task, either a forward blocking or a backward blocking procedure was implemented. Blocking occurred in the causal but not in the predictive scenario. Moreover, blocking was affected by the scenario to the same extent in both age groups. The pattern of results was similar for forward and backward blocking. These results suggest that even young children are sensitive to the causal structure of a contingency learning task and that the occurrence of blocking in such a task defies an explanation in terms of associative learning theory.

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