Towards a Novel no-hair Theorem for Black Holes

We provide strong numerical evidence for a new no-scalar-hair theorem for black holes in general relativity, which rules out spherical scalar hair of static four dimensional black holes if the scalar field theory, when coupled to gravity, satisfies the Positive Energy Theorem. This sheds light on the no-scalar-hair conjecture for Calabi-Yau compactifications of string theory, where the effective potential typically has negative regions but where supersymmetry ensures the total energy is always positive. In theories where the scalar tends to a negative local maximum of the potential at infinity, we find the no-scalar-hair theorem holds provided the asymptotic conditions are invariant under the full anti-de Sitter symmetry group.Comment: 25 pages, 11 figure

New Charged Black Holes with Conformal Scalar Hair

A new class of four-dimensional, hairy, stationary solutions of the Einstein-Maxwell-Lambda system with a conformally coupled scalar field is constructed in this paper. The metric belongs to the Plebanski-Demianski family and hence its static limit has the form of the charged C-metric. It is shown that, in the static case, a new family of hairy black holes arises. They turn out to be cohomogeneity-two, with horizons that are neither Einstein nor homogenous manifolds. The conical singularities in the C-metric can be removed due to the back reaction of the scalar field providing a new kind of regular, radiative spacetime. The scalar field carries a continuous parameter proportional to the usual acceleration present in the C-metric. In the zero-acceleration limit, the static solution reduces to the dyonic Bocharova-Bronnikov-Melnikov-Bekenstein solution or the dyonic extension of the Martinez-Troncoso-Zanelli black holes, depending on the value of the cosmological constant.Comment: Published versio

Coexistence of black holes and a long-range scalar field in cosmology

The exactly solvable scalar hairy black hole model (originated from the modern high-energy theory) is proposed. It turns out that the existence of black holes (BH) is strongly correlated to global scalar field, in a sense that they mutually impose bounds upon their physical parameters like the BH mass (lower bound) or the cosmological constant (upper bound). We consider the same model also as a cosmological one and show that it agrees with recent experimental data; additionally, it provides a unified quintessence-like description of dark energy and dark matter.Comment: 4 pages, 4 figure

Higher-dimensional solitons and black holes with a non-minimally coupled scalar field

We study higher-dimensional soliton and hairy black hole solutions of the Einstein equations non-minimally coupled to a scalar field. The scalar field has no self-interaction potential but a cosmological constant is included. Non-trivial solutions exist only when the cosmological constant is negative and the constant governing the coupling of the scalar field to the Ricci scalar curvature is positive. At least some of these solutions are stable when this coupling constant is not too large.Comment: 17 pages, revtex4, 21 figures, minor changes to match published versio

Black holes in scalar-tensor gravity

Hawking has proven that black holes which are stationary as the endpoint of gravitational collapse in Brans--Dicke theory (without a potential) are no different than in general relativity. We extend this proof to the much more general class of scalar-tensor and f(R) gravity theories, without assuming any symmetries apart from stationarity.Comment: v1: 4 pages; v2: typos corrected, published versio

Conformal couplings of a scalar field to higher curvature terms

We present a simple way of constructing conformal couplings of a scalar field to higher order Euler densities. This is done by constructing a four-rank tensor involving the curvature and derivatives of the field, which transforms covariantly under local Weyl rescalings. The equation of motion for the field, as well as its energy momentum tensor are shown to be of second order. The field equations for the spherically symmetric ansatz are integrated, and for generic non-homogeneous couplings, the solution is given in terms of a polynomial equation, in close analogy with Lovelock theories.Comment: 9 pages, no figures. Based on a talk given by one of the authors at Centro de Estudios Cientificos, Valdivia, Chile, on June 22, 2011. V2: 11 pages, no figures. Typos fixed, appendices and references added. v3: to appear in CQ

THE ROLE OF SIGNALING MOLECULES IN THE DEVELOPMENT OF CHEILITIS CAUSED BY UV IRRADIATION AND SEBORRHEIC ECZEMA

The subject of the study is the establishment of the role of signaling molecules in the development of cheilitis in patients after sensitizing effects on the skin of the red border of the lips of various factors. For this purpose, blood levels of substance P, histamine, tumor necrosis factor-alpha (TNFα) in patients with actinic cheilitis and cheilitis developed against seborrheic eczema were studied. The reliability of the results of clinical and laboratory studies was established by methods of modern statistical processing. It was found that the development of clinical manifestations of lesions of the red border of the lips with sensitizing effects (UV rays and seborrheic process) is reliably associated with a synergistic increase in blood levels of signal molecules of different classes (not opioid neuropeptide, biogenic amine, pro-inflammatory cytokine). The obtained results substantiate new approaches to drawing up plans for examination, treatment and prevention of patients with development of cheilitis after sensitizing effects of UV rays and against seborrheic eczema.Key words: cheilitis (actinic and against the background of seborrheic eczema), signaling molecules (substance P, histamine, TNFα).кандидат медицинских наук, Бочарова В.В., доктор медицинских наук, профессор, Лебедюк М.Н., *доктор медицинских наук, профессор, Бочаров В.А., **доктор медицинских наук, доцент, Куц Л.В. Роль сигнальных молекул в развитии хейлитов, вызванных уф-облучением и себорейной экземой/ Одесский национальный медицинский университет, Украина, Одесса; *Медицинский институт Международного гуманитарного университета, Украина, Одесса; **Медицинский институт Сумского государственного университета, Украина, СумыПредметом исследования является установление роли сигнальных молекул в развитии хейлитов у больных после сенсибилизирующих воздействий на кожу красной каймы губ различных факторов. С этой целью были изучены уровни содержания в крови субстанции Р, гистамина, фактора некроза опухоли-альфа (TNFα) у больных с актиническим хейлитом и хейлитом, развившемся на фоне себорейной экземы. Достоверность результатов клинических и лабораторных исследований устанавливалась методами современной статистической обработки. Выявлено, что развитие клинических проявлений поражения красной каймы губ при сенсибилизирующих воздействиях (УФ-лучей и при себорейном процессе) достоверно связано с синергичным повышением уровней в крови сигнальных молекул разных классов (неопиоидного нейропептида, биогенного амина, провоспалительного цитокина). Полученные результаты обосновывают новые подходы к составлению планов обследования, лечения и профилактики больных с развитием хейлитов после сенсибилизирующих воздействий УФ-лучей и на фоне себорейной экземы.Ключевые слова: хейлиты (актинический и на фоне себорейной экземы), сигнальные молекулы (субстанция Р, гистамин, TNFα).

Dressing a black hole with non-minimally coupled scalar field hair

We investigate the possibility of dressing a four-dimensional black hole with classical scalar field hair which is non-minimally coupled to the space-time curvature. Our model includes a cosmological constant but no self-interaction potential for the scalar field. We are able to rule out black hole hair except when the cosmological constant is negative and the constant governing the coupling to the Ricci scalar curvature is positive. In this case, non-trivial hairy black hole solutions exist, at least some of which are linearly stable. However, when the coupling constant becomes too large, the black hole hair becomes unstable.Comment: 17 pages, 7 figures, uses iopart.cls. Minor changes, accepted for publication in Classical and Quantum Gravit

Cosmology and Static Spherically Symmetric solutions in D-dimensional Scalar Tensor Theories: Some Novel Features

We consider scalar tensor theories in D-dimensional spacetime, D \ge 4. They consist of metric and a non minimally coupled scalar field, with its non minimal coupling characterised by a function. The probes couple minimally to the metric only. We obtain vacuum solutions - both cosmological and static spherically symmetric ones - and study their properties. We find that, as seen by the probes, there is no singularity in the cosmological solutions for a class of functions which obey certain constraints. It turns out that for the same class of functions, there are static spherically symmetric solutions which exhibit novel properties: {\em e.g.} near the ``horizon'', the gravitational force as seen by the probe becomes repulsive.Comment: Revtex. 21 pages. Version 2: More references added. Version 3: Issues raised by the referee are addressed. Results unchanged. Title modified; a new subsection and more references added. Verison to appear in Physical Review