Anti-De Sitter Island-Universes from 5d Standing Waves
NASA Astrophysics Data System (ADS)
Gogberashvili, Merab; Singleton, Douglas
We construct simple standing wave solutions in a 5D spacetime with a ghost-like scalar field. The nodes of these standing waves are "islands" of 4D anti-de Sitter spacetime. In the case of increasing (decreasing) warp factor, there are a finite (infinite) number of nodes and thus a finite (infinite) number of anti-de Sitter island-universes having different gravitational and cosmological constants. This is similar to the landscape models, which postulate a large number of universes with different parameters.
Supersymmetric Kerr-anti-de Sitter solutions
Cvetic, Mirjam; Gao Peng; Simon, Joan
2005-07-15
We prove the existence of one quarter supersymmetric type IIB configurations that arise as nontrivial scaling solutions of the standard five-dimensional Kerr-anti-de Sitter black holes by the explicit construction of its Killing spinors. This neutral, spinning solution is asymptotic to the static anti-de Sitter space-time with cosmological constant -(1/l{sup 2}), it has two finite equal angular momenta J{sub 1}={+-}J{sub 2}, mass M=(1/l)(|J{sub 1}|+|J{sub 2}|) and a naked singularity. We also address the scaling limit associated with one-half supersymmetric solution with only one angular momentum.
Blackfolds in (anti)-de Sitter backgrounds
Armas, Jay; Obers, Niels A.
2011-04-15
We construct different neutral blackfold solutions in Anti-de Sitter and de Sitter background spacetimes in the limit where the cosmological constant is taken to be much smaller than the horizon size. This includes a class of blackfolds with horizons that are products of odd-spheres times a transverse sphere, for which the thermodynamic stability is also studied. Moreover, we exhibit a specific case in which the same blackfold solution can describe different limiting black hole spacetimes therefore illustrating the geometric character of the blackfold approach. Furthermore, we show that the higher-dimensional Kerr-(Anti)-de Sitter black hole allows for ultraspinning regimes in the same limit under consideration and demonstrate that this is correctly described by a pancaked blackfold geometry. We also give evidence for the possibility of saturating the rigidity theorem in these backgrounds.
Liu, James T.; Sabra, W.A.
2005-09-15
The boundary stress tensor approach has proven extremely useful in defining mass and angular momentum in asymptotically anti-de Sitter spaces with CFT duals. An integral part of this method is the use of boundary counterterms to regulate the gravitational action and stress tensor. In the presence of matter, however, ambiguities may arise that are related to the addition of possible finite counterterms. We demonstrate this explicitly for R-charged black holes in AdS{sub 5}, where introduction of a finite counterterm proportional to {phi}{sup 2} is necessary to properly reproduce the expected mass/charge relation for the black holes.
Colorful Horizons with Charge in Anti-de Sitter Space
Gubser, Steven S.
2008-11-07
An Abelian gauge symmetry can be spontaneously broken near a black hole horizon in anti-de Sitter space using a condensate of non-Abelian gauge fields. A second order phase transition is shown to separate Reissner-Nordstroem-anti-de Sitter solutions from a family of symmetry-breaking solutions which preserve a diagonal combination of gauge invariance and spatial rotational invariance.
Farakos, K.; Kouretsis, A. P.; Pasipoularides, P.
2009-09-15
We construct asymptotically AdS black hole solutions, with a self-interacting bulk scalar field, in the context of 5D general relativity. As the observable universe is characterized by spatial flatness, we focus on solutions where the horizon of the black hole, and subsequently all 3D hypersurfaces for fixed radial coordinate, have zero spatial curvature. We examine two cases for the black hole scalar hair: (a) an exponential decaying scalar field profile and (b) an inverse power scalar field profile. The scalar black hole solutions we present in this paper are characterized by four functions f(r), a(r), {phi}(r), and V({phi}(r)). Only the functions {phi}(r) and a(r) are determined analytically, while the functions f(r) and V({phi}(r)) are expressed semianalytically by integral formulas in terms of a(r). We present our numerical results and study in detail the characteristic properties of our solutions. We also note that the potential we obtain has a nonconvex form in agreement with the corresponding 'no hair theorem' for AdS spacetimes.
NASA Astrophysics Data System (ADS)
Farakos, K.; Kouretsis, A. P.; Pasipoularides, P.
2009-09-01
We construct asymptotically AdS black hole solutions, with a self-interacting bulk scalar field, in the context of 5D general relativity. As the observable universe is characterized by spatial flatness, we focus on solutions where the horizon of the black hole, and subsequently all 3D hypersurfaces for fixed radial coordinate, have zero spatial curvature. We examine two cases for the black hole scalar hair: (a) an exponential decaying scalar field profile and (b) an inverse power scalar field profile. The scalar black hole solutions we present in this paper are characterized by four functions f(r), a(r), ϕ(r), and V(ϕ(r)). Only the functions ϕ(r) and a(r) are determined analytically, while the functions f(r) and V(ϕ(r)) are expressed semianalytically by integral formulas in terms of a(r). We present our numerical results and study in detail the characteristic properties of our solutions. We also note that the potential we obtain has a nonconvex form in agreement with the corresponding “no hair theorem” for AdS spacetimes.
Small Kerr-anti-de Sitter black holes are unstable
Cardoso, Vitor; Dias, Oscar J.C.
2004-10-15
Superradiance in black hole spacetimes can trigger instabilities. Here we show that, due to superradiance, small Kerr-anti-de Sitter black holes are unstable. Our demonstration uses a matching procedure, in a long wavelength approximation.
NASA Astrophysics Data System (ADS)
Arzano, Michele; Gubitosi, Giulia; Magueijo, João; Amelino-Camelia, Giovanni
2015-07-01
We investigate the anti-de Sitter (AdS) counterpart to the well-studied de Sitter (dS) model for energy-momentum space, viz "κ -momentum space" space (with a structure based on the properties of the κ -Poincaré Hopf algebra). On the basis of previous preliminary results one might expect the two models to be complementary: dS exhibiting an invariant maximal spatial momentum but unbounded energy, AdS a maximal energy but unbounded momentum. If that were the case AdS momentum space could be used to implement a principle of maximal Planck-scale energy, just as several studies use dS momentum space to postulate of maximal Planck-scale spatial momentum. However, several unexpected features are uncovered in this paper, which limit the scope of the expected complementarity, and interestingly they take different forms in different coordinatizations of AdS momentum space. "Cosmological" AdS coordinates mimic the dS construction used for κ -momentum space, and produce a Carrol limit in the ultraviolet. However, unlike the κ -momentum space, the boundary of the covered patch breaks Lorentz invariance, thereby introducing a preferred frame. In "horospherical" coordinates we achieve full consistency with frame independence as far as boost transformations are concerned, but find that rotational symmetry is broken, leading to an anisotropic model for the speed of light. Finally, in "static" coordinates we find a way of deforming relativistic transformations that successfully enforces frame invariance and isotropy, and produces a Carrol limit in the ultraviolet. Our results are also relevant for a long-standing debate on whether or not coordinate redefinitions in momentum space lead to physically equivalent theories: our three proposals are evidently physically inequivalent, leading to alternative models of Planck-scale effects. As a corollary we study the UV running of the Hausdorff dimension of momentum space in the first and third model, obtaining different results.
The Schwinger mechanism in (Anti) de Sitter spacetimes
NASA Astrophysics Data System (ADS)
Samantray, Prasant
2016-04-01
We present a short and novel derivation of the Schwinger mechanism for particle pair production in 1 + 1 dimensional de Sitter and Anti de Sitter spacetimes. We work directly in the flat embedding space and derive the pair production rates in these spacetimes via instanton methods. The derivation is manifestly coordinate independent, and also lends support to the possible deep connection between two conceptually disparate quantum phenomena — Schwinger effect and the Davies-Unruh effect.
On electric field in anti-de Sitter spacetime
Cheong, Lee Yen E-mail: chewxy01813@gmail.com Yan, Chew Xiao E-mail: chewxy01813@gmail.com Ching, Dennis Ling Chuan E-mail: chewxy01813@gmail.com
2014-10-24
In this paper we calculate the electromagnetic field produced using retarded Green's function in Anti-de Sitter spacetime (AdS). Since this spacetime is non-globally hyperbolic and has no Cauchy surface, we only consider the field originated from a charge moving along its geodesic in the region consists of points covered by future null geodesic of the charge.
Superradiant instabilities of asymptotically anti-de Sitter black holes
NASA Astrophysics Data System (ADS)
Green, Stephen R.; Hollands, Stefan; Ishibashi, Akihiro; Wald, Robert M.
2016-06-01
We study the linear stability of asymptotically anti-de Sitter black holes in general relativity in spacetime dimension d≥slant 4. Our approach is an adaptation of the general framework of Hollands and Wald, which gives a stability criterion in terms of the sign of the canonical energy, { E }. The general framework was originally formulated for static or stationary and axisymmetric black holes in the asymptotically flat case, and the stability analysis for that case applies only to axisymmetric perturbations. However, in the asymptotically anti-de Sitter case, the stability analysis requires only that the black hole have a single Killing field normal to the horizon and there are no restrictions on the perturbations (apart from smoothness and appropriate behavior at infinity). For an asymptotically anti-de Sitter black hole, we define an ergoregion to be a region where the horizon Killing field is spacelike; such a region, if present, would normally occur near infinity. We show that for black holes with ergoregions, initial data can be constructed such that { E }\\lt 0, so all such black holes are unstable. To obtain such initial data, we first construct an approximate solution to the constraint equations using the WKB method, and then we use the Corvino–Schoen technique to obtain an exact solution. We also discuss the case of charged asymptotically anti-de Sitter black holes with generalized ergoregions.
The anti-de Sitter spacetime as a time machine
NASA Astrophysics Data System (ADS)
Ahmed, Faizuddin; Bikash Hazarika, Bidyut; Sarma, Debojit
2016-07-01
We construct an axially symmetric spacetime admitting, after a certain instant, closed timelike curves (CTCs) indicating that it is a time-machine spacetime. The spacetime, which is locally anti-de Sitter, is a four-dimensional extension of the Misner space with identical causality-violating properties. In this spacetime, CTCs evolve from a casually well-behaved initial hypersurface.
Photon rockets in the (anti-)de Sitter universe
Podolsky, J.
2008-08-15
A class of exact solutions to Einstein's equations is presented, which describes accelerating photon rockets in the de Sitter and anti-de Sitter universes. These are particular members of the Robinson-Trautman family of axially symmetric spacetimes with pure radiation. In particular, generalizations of (type D) Kinnersley's rockets and (type II) Bonnor's rockets to the case of a nonvanishing cosmological constant are given. Some of the main physical properties of these solutions are investigated, and their relation to the C-metric solution which describes uniformly accelerated black holes is also given.
Dirac fermions on an anti-de Sitter background
Ambruş, Victor E. Winstanley, Elizabeth
2014-11-24
Using an exact expression for the bi-spinor of parallel transport, we construct the Feynman propagator for Dirac fermions in the vacuum state on anti-de Sitter space-time. We compute the vacuum expectation value of the stress-energy tensor by removing coincidence-limit divergences using the Hadamard method. We then use the vacuum Feynman propagator to compute thermal expectation values at finite temperature. We end with a discussion of rigidly rotating thermal states.
Evanescent gravitons in warped anti-de Sitter space
NASA Astrophysics Data System (ADS)
Giribet, Gaston; Vásquez, Yerko
2016-01-01
Besides black holes, the phase space of three-dimensional massive gravity about warped anti-de Sitter space contains solutions that decay exponentially in time. They describe evanescent graviton configurations that, while governed by a wave equation with nonvanishing effective mass, do not carry net gravitational energy. Explicit examples of such solutions have been found in the case of topologically massive gravity; here, we generalize them to a much more general ghost-free massive deformation, with the difference being that the decay rate gets corrected due to the presence of higher-order terms.
Cosmic censorship of rotating Anti-de Sitter black hole
NASA Astrophysics Data System (ADS)
Gwak, Bogeun; Lee, Bum-Hoon
2016-02-01
We test the validity of cosmic censorship in the rotating anti-de Sitter black hole. For this purpose, we investigate whether the extremal black hole can be overspun by the particle absorption. The particle absorption will change the mass and angular momentum of the black hole, which is analyzed using the Hamilton-Jacobi equations consistent with the laws of thermodynamics. We have found that the mass of the extremal black hole increases more than the angular momentum. Therefore, the outer horizon of the black hole still exists, and cosmic censorship is valid.
Lightlike hypersurfaces along spacelike submanifolds in anti-de Sitter space
Izumiya, Shyuichi
2015-11-15
Anti-de Sitter space is the Lorentzian space form with negative curvature. In this paper, we consider lightlike hypersurfaces along spacelike submanifolds in anti-de Sitter space with general codimension. In particular, we investigate the singularities of lightlike hypersurfaces as an application of the theory of Legendrian singularities.
Generalized Gravitational Entropy for Warped Anti-de Sitter Space
NASA Astrophysics Data System (ADS)
Song, Wei; Wen, Qiang; Xu, Jianfei
2016-07-01
For spacetimes that are not asymptotic to anti-de Sitter (non AAdS) space, we adapt the Lewkowycz-Maldacena procedure to find the holographic entanglement entropy. The key observation, which to our knowledge is not very well appreciated, is that asymptotic boundary conditions play an essential role on extending the replica trick to the bulk. For non AAdS, we expect the following three main modifications: (1) the expansion near the special surface has to be compatible with the asymptotic expansion; (2) periodic conditions are imposed to coordinates on the phase space with diagonalized symplectic structure, not to all fields appearing in the action; (3) evaluating the entanglement functional using the boundary term method amounts to evaluating the presymplectic structure at the special surface, where some additional exact form may contribute. An explicit calculation is carried out for three-dimensional warped anti-de Sitter spacetime (WAdS3 ) in a consistent truncation of string theory, the so-called S -dual dipole theory. It turns out that the generalized gravitational entropy in WAdS3 is captured by the least action of a charged particle in WAdS3 space, or equivalently, by the geodesic length in an auxiliary AdS3 . Consequently, the bulk calculation agrees with the CFT results, providing another piece of evidence for the WAdS3/CFT2 correspondence.
Generalized Gravitational Entropy for Warped Anti-de Sitter Space.
Song, Wei; Wen, Qiang; Xu, Jianfei
2016-07-01
For spacetimes that are not asymptotic to anti-de Sitter (non AAdS) space, we adapt the Lewkowycz-Maldacena procedure to find the holographic entanglement entropy. The key observation, which to our knowledge is not very well appreciated, is that asymptotic boundary conditions play an essential role on extending the replica trick to the bulk. For non AAdS, we expect the following three main modifications: (1) the expansion near the special surface has to be compatible with the asymptotic expansion; (2) periodic conditions are imposed to coordinates on the phase space with diagonalized symplectic structure, not to all fields appearing in the action; (3) evaluating the entanglement functional using the boundary term method amounts to evaluating the presymplectic structure at the special surface, where some additional exact form may contribute. An explicit calculation is carried out for three-dimensional warped anti-de Sitter spacetime (WAdS_{3}) in a consistent truncation of string theory, the so-called S-dual dipole theory. It turns out that the generalized gravitational entropy in WAdS_{3} is captured by the least action of a charged particle in WAdS_{3} space, or equivalently, by the geodesic length in an auxiliary AdS_{3}. Consequently, the bulk calculation agrees with the CFT results, providing another piece of evidence for the WAdS_{3}/CFT_{2} correspondence. PMID:27419559
(Anti-) de Sitter electrically charged black-hole solutions in higher-derivative gravity
NASA Astrophysics Data System (ADS)
Lin, Kai; Qian, Wei-Liang; Pavan, A. B.; Abdalla, E.
2016-06-01
In this paper, static electrically charged black-hole solutions with cosmological constant are investigated in an Einstein-Hilbert theory of gravity with additional quadratic curvature terms. Beside the analytic Schwarzschild (Anti-) de Sitter solutions, non-Schwarzschild (Anti-) de Sitter solutions are also obtained numerically by employing the shooting method. The results show that there exist two groups of asymptotically (Anti-) de Sitter spacetimes for both charged and uncharged black holes. In particular, it was found that for uncharged black holes the first group can be reduced to the Schwarzschild (Anti-) de Sitter solution, while the second group is intrinsically different from a Schwarzschild (Anti-) de Sitter solution even when the charge and the cosmological constant become zero.
Gravitational collapse in asymptotically anti-de Sitter or de Sitter backgrounds
Madhav, T. Arun; Goswami, Rituparno; Joshi, Pankaj S.
2005-10-15
We study here the gravitational collapse of a matter cloud with a nonvanishing tangential pressure in the presence of a nonzero cosmological term {lambda}. It is investigated how {lambda} modifies the dynamics of the collapsing cloud and whether it affects the cosmic censorship. Conditions for bounce and singularity formation are derived. It is seen that when the tangential pressure vanishes, the bounce and singularity conditions reduce to the dust case studied earlier. The collapsing interior is matched to an exterior which is asymptotically de Sitter or anti-de Sitter, depending on the sign of the cosmological constant. The junction conditions for matching the cloud to the exterior are specified. The effect of {lambda} on apparent horizons is studied in some detail and the nature of central singularity is analyzed. The visibility of singularity and implications for the cosmic censorship conjecture are discussed. It is shown that for a nonvanishing cosmological constant, both black hole and naked singularities do form as collapse end states in spacetimes which are asymptotically de Sitter or anti-de Sitter.
NUT charge, anti-de Sitter space, and entropy
NASA Astrophysics Data System (ADS)
Hawking, S. W.; Hunter, C. J.; Page, Don N.
1999-02-01
It has been proposed that spacetimes with a U(1) isometry group have contributions to the entropy from Misner strings as well as from the area of d-2 dimensional fixed point sets. In this paper we test this proposal by constructing Taub-NUT-AdS and Taub-bolt-AdS solutions which are examples of a new class of asymptotically locally anti-de Sitter space. We find that with the additional contribution from the Misner strings, we exactly reproduce the entropy calculated from the action by the usual thermodynamic relations. This entropy has the right parameter dependence to agree with the entropy of a conformal field theory on the boundary, which is a squashed three-sphere, at least in the limit of large squashing. However, the conformal field theory and the normalization of the entropy remain to be determined.
Holographic entanglement entropy for noncommutative anti-de Sitter space
NASA Astrophysics Data System (ADS)
Momeni, Davood; Raza, Muhammad; Myrzakulov, Ratbay
2016-04-01
A metric is proposed to explore the noncommutative form of the anti-de Sitter (AdS) space due to quantum effects. It has been proved that the noncommutativity in AdS space induces a single component gravitoelectric field. The holographic Ryu-Takayanagi (RT) algorithm is then applied to compute the entanglement entropy (EE) in dual CFT2. This calculation can be exploited to compute ultraviolet-infrared (UV-IR) cutoff dependent central charge of the certain noncommutative CFT2. This noncommutative computation of the EE can be interpreted in the form of the surface/state correspondence. We have shown that noncommutativity increases the dimension of the effective Hilbert space of the dual conformal field theory (CFT).
Normalized energy eigenspinors of the Dirac field on anti-de Sitter spacetime
NASA Astrophysics Data System (ADS)
Cotăescu, Ion I.
1999-12-01
I show how to derive the normalized energy eigenspinors of the free Dirac field on anti-de Sitter spacetime by using a Cartesian tetrad gauge where the separation of spherical variables can be done as in special relativity.
Chemical potential driven phase transition of black holes in anti-de Sitter space
NASA Astrophysics Data System (ADS)
Galante, Mario; Giribet, Gaston; Goya, Andrés; Oliva, Julio
2015-11-01
Einstein-Maxwell theory conformally coupled to a scalar field in D dimensions may exhibit a phase transition at low temperature whose end point is an asymptotically anti-de Sitter black hole with a scalar field profile that is regular everywhere outside and on the horizon. This provides a tractable model to study the phase transition of hairy black holes in anti-de Sitter space in which the backreaction on the geometry can be solved analytically.
Einstein-Maxwell-Anti-de-Sitter spinning solitons
NASA Astrophysics Data System (ADS)
Herdeiro, Carlos; Radu, Eugen
2016-06-01
Electrostatics on global Anti-de-Sitter (AdS) spacetime is sharply different from that on global Minkowski spacetime. It admits a multipolar expansion with everywhere regular, finite energy solutions, for every multipole moment except the monopole [1]. A similar statement holds for global AdS magnetostatics. We show that everywhere regular, finite energy, electric plus magnetic fields exist on AdS in three distinct classes: (I) with non-vanishing total angular momentum J; (II) with vanishing J but non-zero angular momentum density, Tφt ; (III) with vanishing J and Tφt . Considering backreaction, these configurations remain everywhere smooth and finite energy, and we find, for example, Einstein-Maxwell-AdS solitons that are globally - Type I - or locally (but not globally) - Type II - spinning. This backreaction is considered first perturbatively, using analytical methods and then non-perturbatively, by constructing numerical solutions of the fully non-linear Einstein-Maxwell-AdS system. The variation of the energy and total angular momentum with the boundary data is explicitly exhibited for one example of a spinning soliton.
Simulation of Black Hole Collisions in Asymptotically Anti-de Sitter Spacetimes
NASA Astrophysics Data System (ADS)
Bantilan, Hans; Romatschke, Paul
2015-02-01
We present results from the evolution of spacetimes that describe the merger of asymptotically global anti-de Sitter black holes in 5D with an SO(3) symmetry. Prompt scalar field collapse provides us with a mechanism for producing distinct trapped regions on the initial slice, associated with black holes initially at rest. We evolve these black holes towards a merger, and follow the subsequent ring down. The boundary stress tensor of the dual conformal field theory is conformally related to a stress tensor in Minkowski space that inherits an axial symmetry from the bulk SO(3). We compare this boundary stress tensor to its hydrodynamic counterpart with viscous corrections of up to second order, and compare the conformally related stress tensor to ideal hydrodynamic simulations in Minkowski space, initialized at various time slices of the boundary data. Our findings reveal far-from-hydrodynamic behavior at early times, with a transition to ideal hydrodynamics at late times.
Simulation of black hole collisions in asymptotically Anti-de Sitter spacetimes.
Bantilan, Hans; Romatschke, Paul
2015-02-27
We present results from the evolution of spacetimes that describe the merger of asymptotically global anti-de Sitter black holes in 5D with an SO(3) symmetry. Prompt scalar field collapse provides us with a mechanism for producing distinct trapped regions on the initial slice, associated with black holes initially at rest. We evolve these black holes towards a merger, and follow the subsequent ring down. The boundary stress tensor of the dual conformal field theory is conformally related to a stress tensor in Minkowski space that inherits an axial symmetry from the bulk SO(3). We compare this boundary stress tensor to its hydrodynamic counterpart with viscous corrections of up to second order, and compare the conformally related stress tensor to ideal hydrodynamic simulations in Minkowski space, initialized at various time slices of the boundary data. Our findings reveal far-from-hydrodynamic behavior at early times, with a transition to ideal hydrodynamics at late times. PMID:25768753
Semiclassical quantization of circular strings in de Sitter and anti--de Sitter spacetimes
de Vega, H.J. |; Larsen, A.L.; Sanchez, N.
1995-06-15
We compute the {ital exact} equation of state of circular strings in the (2+1)--dimensional de Sitter (dS) and anti--de Sitter (AdS) spacetimes, and analyze its properties for the different (oscillating, contracting, and expanding) strings. The string equation of state has the perfect fluid form {ital P}=({gamma}{minus}1){ital E}, with the pressure and energy expressed closely and completely in terms of elliptic functions, the instantaneous coefficient {gamma} depending on the elliptic modulus. We semiclassically quantize the oscillating circular strings. The string mass is {ital m}= {radical}{ital C} /({pi}{ital H}{alpha}{prime}), {ital C} being the Casimir operator, {ital C}={minus}{ital L}{sub {mu}{nu}}{ital L}{sup {mu}{nu}}, of the O(3,1)-dS [O(2,2)-AdS] group, and {ital H} is the Hubble constant. We find {alpha}{prime}{ital m}{sub dS}{sup 2}{approx}4{ital n}{minus}5{ital H}{sup 2}{alpha}{prime}{ital n}{sup 2} ({ital n}{element_of}{ital N}{sub 0}), and a {ital finite} number of states {ital N}{sub dS}{approx}0.34/({ital H}{sup 2}{alpha}{prime}) in de Sitter spacetime; {ital m}{sub AdS}{sup 2}{approx}{ital H}{sup 2}{ital n}{sup 2} (large {ital n}{element_of}{ital N}{sub 0}) and {ital N}{sub AdS}={infinity} in anti--de Sitter spacetime. The level spacing grows with {ital n} in AdS spacetime, while it is approximately constant (although smaller than in Minkowski spacetime and slightly decreasing) in dS spacetime. The massive states in dS spacetime decay through the tunnel effect and the semiclassical decay probability is computed. The semiclassical quantization of {ital exact} (circular) strings and the canonical quantization of generic string perturbations around the string center of mass qualitatively agree.
Deformations of anti-de Sitter black holes
NASA Astrophysics Data System (ADS)
Detournay, Stephane
2006-11-01
This PhD thesis mainly deals with deformations of locally anti-de Sitter black holes, focusing in particular on BTZ black holes. We first study the generic rotating and (extended) non-rotating BTZ black holes within a pseudo-Riemannian symmetric spaces framework, emphasize on the role played by solvable subgroups of SL(2,R) in the black hole structure and derive their global geometry in a group-theoretical way. We analyse how these observations are transposed in the case of higher-dimensional locally AdS black holes. We then show that there exists, in SL(2,R), a family of twisted conjugacy classes which give rise to winding symmetric WZW D1-branes in a BTZ black hole background. The term "deformation" is then considered in two distinct ways. On the one hand, we deform the algebra of functions on the branes in the sense of (strict) deformation quantization, giving rise to a "noncommutative black hole". In the same context, we investigate the question of invariant deformations of the hyperbolic plane and present explicit formulae. On the other hand, we explore the moduli space of the (orbifolded) SL(2,R) WZW model by studying its marginal deformations, yielding namely a new class of exact black string solutions in string theory. These deformations also allow us to relate the D1-branes in BTZ black holes to D0-branes in the 2D black hole. A fair proportion of this thesis consists of (hopefully) pedagogical short introductions to various subjects: deformation quantization, string theory, WZW models, symmetric spaces, symplectic and Poisson geometry.
Semiclassical (qft) and Quantum (string) Anti-De Sitter Regimes:. New Results
NASA Astrophysics Data System (ADS)
Bouchareb, A.; Ramón Medrano, M.; Sánchez, N. G.
We compute the quantum string entropy Ss(m, H) from the microscopic string density of states ρs(m, H) of mass m in Anti-de Sitter space-time. For high m, (high Hm → c/α‧), no phase transition occurs at the Anti-de Sitter string temperature Ts = (1/2πkB)Lclc2/α‧, which is higher than the flat space (Hagedorn) temperature ts. (Lcl = c/H, the Hubble constant H acts as producing a smaller string constant α‧ and thus, a higher tension). Ts is the precise quantum dual of the semiclassical (QFT) Anti-de Sitter temperature scale Tsem = ℏc/(2πkBLcl). We compute the quantum string emission σstring by a black hole in Anti-de Sitter (or asymptotically Anti-de Sitter) space-time (bhAdS). For Tsem bhAdS ≪ Ts (early evaporation stage), it shows the QFT Hawking emission with temperature Tsem bhAdS (semiclassical regime). For Tsem bhAdS → Ts, it exhibits a phase transition into a Anti-de Sitter string state of size Ls = ls2/L_ cl, (ls = √ hbar α '/c}), and Anti-de Sitter string temperature Ts. New string bounds on the black hole emerge in the bhAdS string regime. The bhAdS string regime determines a maximal value for H : Hmax = 0.841c/ls. The minimal black hole radius in Anti-de Sitter space-time turns out to be rg min = 0.841ls, and is larger than the minimal black hole radius in de Sitter space-time by a numerical factor equal to 2.304. We find a new formula for the full AdS entropy Ssem(H), as a function of the usual Bekenstein-Hawking entropy S sem(0)(H). For Lcl ≫ ℓPlanck, i.e. for low H ≪ c/ℓPlanck, or classical regime, S sem(0)(H) is the leading term with its logarithmic correction, but for high H ≥ c/ℓPlanck or quantum regime, no phase transition operates, in contrast to de Sitter space, and the entropy Ssem(H) is very different from the Bekenstein-Hawking term S sem(0)(H).
Phase space localization for anti-de Sitter quantum mechanics and its zero curvature limit
NASA Technical Reports Server (NTRS)
Elgradechi, Amine M.
1993-01-01
Using techniques of geometric quantization and SO(sub 0)(3,2)-coherent states, a notion of optimal localization on phase space is defined for the quantum theory of a massive and spinning particle in anti-de Sitter space time. It is shown that this notion disappears in the zero curvature limit, providing one with a concrete example of the regularizing character of the constant (nonzero) curvature of the anti-de Sitter space time. As a byproduct a geometric characterization of masslessness is obtained.
Kar, Supriya
2006-12-15
We obtain de Sitter (dS) and anti-de Sitter (AdS) generalized Reissner-Nordstrom-like black hole geometries in a curved D{sub 3}-brane framework, underlying a noncommutative gauge theory on the brane world. The noncommutative scaling limit is explored to investigate a possible tunneling of an AdS vacuum in string theory to dS vacuum in its low energy gravity theory. The Hagedorn transition is invoked into its self-dual gauge theory to decouple the gauge nonlinearity from the dS geometry, which in turn is shown to describe a pure dS vacuum.
Discrete Torsion, (Anti) de Sitter D4-Brane and Tunneling
NASA Astrophysics Data System (ADS)
Singh, Abhishek K.; Pandey, P. K.; Singh, Sunita; Kar, Supriya
2014-06-01
We obtain quantum geometries on a vacuum created pair of a (DDbar)3-brane, at a Big Bang singularity, by a local two form on a D4-brane. In fact our analysis is provoked by an established phenomenon leading to a pair creation by a gauge field at a black hole horizon by Stephen Hawking in 1975. Importantly, the five dimensional microscopic black holes are described by an effective non-perturbative curvature underlying a discrete torsion in a second order formalism. In the case for a non-propagating torsion, the effective curvature reduces to Riemannian, which in a low energy limit may describe Einstein vacuum in the formalism. In particular, our analysis suggests that a non-trivial space begin with a hot de Sitter brane-Universe underlying a nucleation of a vacuum pair of (DDbar)-instanton at a Big Bang. A pair of instanton nucleats a D-particle which in turn combines with an anti D-particle to describe a D-string and so on. The nucleation of a pair of higher dimensional pair of brane/anti-brane from a lower dimensional pair may be viewed via an expansion of the brane-Universe upon time. It is in conformity with the conjecture of a branes within a brane presumably in presence of the non-zero modes of two form. Interestingly, we perform a thermal analysis underlying various emergent quantum de Sitter vacua on a D4-brane and argue for the plausible tunneling geometries underlying a thermal equilibrium. It is argued that a de Sitter Schwarzschild undergoes quantum tunneling to an AdS-brane Schwarzschild via Nariai and de Sitter topological black hole.
Entanglement entropy of black holes and anti-de Sitter space/conformal-field-theory correspondence.
Solodukhin, Sergey N
2006-11-17
A recent proposal by Ryu and Takayanagi for a holographic interpretation of entanglement entropy in conformal field theories dual to supergravity on anti-de Sitter space is generalized to include entanglement entropy of black holes living on the boundary of anti-de Sitter space. The generalized proposal is verified in boundary dimensions d=2 and d=4 for both the uv-divergent and uv-finite terms. In dimension d=4 an expansion of entanglement entropy in terms of size L of the subsystem outside the black hole is considered. A new term in the entropy of dual strongly coupled conformal-field theory, which universally grows as L(2)lnL and is proportional to the value of the obstruction tensor at the black hole horizon, is predicted. PMID:17155672
Stability of anti-de sitter space in Einstein-Gauss-Bonnet gravity.
Deppe, Nils; Kolly, Allison; Frey, Andrew; Kunstatter, Gabor
2015-02-20
Recently it has been argued that in Einstein gravity anti-de Sitter spacetime is unstable against the formation of black holes for a large class of arbitrarily small perturbations. We examine the effects of including a Gauss-Bonnet term. In five dimensions, spherically symmetric Einstein-Gauss-Bonnet gravity has two key features: Choptuik scaling exhibits a radius gap, and the mass function goes to a finite value as the horizon radius vanishes. These suggest that black holes will not form dynamically if the total mass-energy content of the spacetime is too small, thereby restoring the stability of anti-de Sitter spacetime in this context. We support this claim with numerical simulations and uncover a rich structure in horizon radii and formation times as a function of perturbation amplitude. PMID:25763946
The anti-de Sitter Gott universe: a rotating BTZ wormhole
NASA Astrophysics Data System (ADS)
Holst, Sören; Matschull, Hans-Jürgen
1999-10-01
Recently, it has been shown that a (2 + 1)-dimensional black hole can be created by the collapse of two colliding massless particles in an otherwise empty anti-de Sitter space. Here we generalize this construction to the case of a non-zero impact parameter. The resulting spacetime, which may be regarded as a Gott universe in an anti-de Sitter background, contains closed timelike curves. By treating these as singular we are able to interpret our solution as a rotating black hole, hence providing a link between the Gott universe and the BTZ black hole. When analysing the spacetime we see how the full causal structure of the interior can be almost completely inferred just from considerations of the conformal boundary.
NASA Astrophysics Data System (ADS)
Rahaman, Farook; Bhar, Piyali; Sharma, Ranjan; Tiwari, Rishi Kumar
2015-03-01
We report a -D charged black hole solution in an anti-de Sitter space inspired by noncommutative geometry. In this construction, the black hole exhibits two horizons, which turn into a single horizon in the extreme case. We investigate the impacts of electromagnetic field on the location of the event horizon, mass and thermodynamic properties such as Hawking temperature, entropy, and heat capacity of the black hole. The geodesics of the charged black hole are also analyzed.
Resonant Dynamics and the Instability of Anti-de Sitter Spacetime.
Bizoń, Piotr; Maliborski, Maciej; Rostworowski, Andrzej
2015-08-21
We consider spherically symmetric Einstein-massless-scalar field equations with a negative cosmological constant in five dimensions and analyze the evolution of small perturbations of anti-de Sitter (AdS) spacetime using the recently proposed resonant approximation. We show that for typical initial data the solution of the resonant system develops an oscillatory singularity in finite time. This result hints at a possible route to establishing the instability of AdS under arbitrarily small perturbations. PMID:26340178
Anti-de Sitter-wave solutions of higher derivative theories.
Gürses, Metin; Hervik, Sigbjørn; Şişman, Tahsin Çağrı; Tekin, Bayram
2013-09-01
We show that the recently found anti-de Sitter (AdS)-plane and AdS-spherical wave solutions of quadratic curvature gravity also solve the most general higher derivative theory in D dimensions. More generally, we show that the field equations of such theories reduce to an equation linear in the Ricci tensor for Kerr-Schild spacetimes having type-N Weyl and type-N traceless Ricci tensors. PMID:25166648
Resonant Dynamics and the Instability of Anti-de Sitter Spacetime
NASA Astrophysics Data System (ADS)
Bizoń, Piotr; Maliborski, Maciej; Rostworowski, Andrzej
2015-08-01
We consider spherically symmetric Einstein-massless-scalar field equations with a negative cosmological constant in five dimensions and analyze the evolution of small perturbations of anti-de Sitter (AdS) spacetime using the recently proposed resonant approximation. We show that for typical initial data the solution of the resonant system develops an oscillatory singularity in finite time. This result hints at a possible route to establishing the instability of AdS under arbitrarily small perturbations.
Recursive Techniques for Computing Gluon Scattering in Anti-de-Sitter Space
NASA Astrophysics Data System (ADS)
Shyaka, Claude; Kharel, Savan
2016-03-01
The anti-de Sitter/conformal field theory correspondence is a relationship between two kinds of physical theories. On one side of the duality are special type of quantum (conformal) field theories known as the Yang-Mills theory. These quantum field theories are known to be equivalent to theories of gravity in Anti-de Sitter (AdS) space. The physical observables in the theory are the correlation functions that live in the boundary of AdS space. In general correlation functions are computed using configuration space and the expressions are extremely complicated. Using momentum basis and recursive techniques developed by Raju, we extend tree level correlation functions for four and five-point correlation functions in Yang-Mills theory in Anti-de Sitter space. In addition, we show that for certain external helicity, the correlation functions have simple analytic structure. Finally, we discuss how one can generalize these results to n-point functions. Hendrix college odyssey Grant.
Toroidal configurations of perfect fluid in the Reissner-Nordström-(anti-)de Sitter spacetimes
Kucáková, Hana; Slaný, Petr; Stuchlík, Zdenĕk E-mail: petr.slany@fpf.slu.cz
2011-01-01
Influence of cosmological constant on toroidal fluid configurations around charged spherically symmetric black holes and naked singularities is demostrated by study of perfect-fluid tori with uniform distribution of specific angular momentum orbiting in the Reissner-Nordström-(anti-)de Sitter spacetimes. Toroidal configurations are allowed only in the spacetimes admitting existence of stable circular geodesics. Configurations with marginally closed equipotential (equipressure) surfaces crossing itself in a cusp allow accretion (through the inner cusp) and/or excretion (through the outer cusp) of matter from the toroidal configuration. Detailed classification of the Reissner-Nordström-(anti-)de Sitter spacetimes according to properties of the marginally stable tori is given. It is demonstrated that in the Reissner-Nordström-de Sitter naked-singularity spacetimes an interesting phenomenon of doubled tori can exist enabling exchange of matter between two tori in both inward and outward directions. In naked-singularity spacetimes the accretion onto the central singularity is impossible due to existence of a potential barrier.
Generic cosmic-censorship violation in anti-de Sitter space.
Hertog, Thomas; Horowitz, Gary T; Maeda, Kengo
2004-04-01
We consider (four-dimensional) gravity coupled to a scalar field with potential V(phi). The potential satisfies the positive energy theorem for solutions that asymptotically tend to a negative local minimum. We show that for a large class of such potentials, there is an open set of smooth initial data that evolve to naked singularities. Hence cosmic censorship does not hold for certain reasonable matter theories in asymptotically anti-de Sitter spacetimes. The asymptotically flat case is more subtle. We suspect that potentials with a local Minkowski minimum may similarly lead to violations of cosmic censorship in asymptotically flat spacetimes, but we do not have definite results. PMID:15089592
Anyonic Strings and Membranes in Anti-de Sitter Space and Dual Aharonov-Bohm Effects
Hartnoll, Sean A.
2007-03-16
It is observed that strings in AdS{sub 5}xS{sup 5} and membranes in AdS{sub 7}xS{sup 4} exhibit long range phase interactions. Two well separated membranes dragged around one another in anti-de Sitter space (AdS) acquire phases of 2{pi}/N. The same phases are acquired by a well separated F and D string dragged around one another. The phases are shown to correspond to both the standard and a novel type of Aharonov-Bohm effect in the dual field theory.
Bjorken flow from an anti-de Sitter space Schwarzschild black hole.
Alsup, James; Siopsis, George
2008-07-18
We consider a large black hole in asymptotically anti-de Sitter spacetime of arbitrary dimension with a Minkowski boundary. By performing an appropriate slicing as we approach the boundary, we obtain via holographic renormalization a gauge theory fluid obeying Bjorken hydrodynamics in the limit of large longitudinal proper time. The metric we obtain reproduces to leading order the metric recently found as a direct solution of the Einstein equations in five dimensions. Our results are also in agreement with recent exact results in three dimensions. PMID:18764245
Massive higher derivative gravity in D-dimensional anti-de Sitter spacetimes
Guellue, Ibrahim; Tekin, Bayram
2009-09-15
We find the propagator and calculate the tree level scattering amplitude between two covariantly conserved sources in an anti-de Sitter background for the most general D-dimensional quadratic, four-derivative, gravity with a Pauli-Fierz mass. We also calculate the Newtonian potential for various limits of the theory in flat space. We show how the recently introduced three-dimensional New Massive Gravity is uniquely singled out among higher derivative models as a (tree level) unitary model and that its Newtonian limit is equivalent to that of the usual massive gravity in flat space.
Anti-de Sitter-Space/Conformal-Field-Theory Casimir Energy for Rotating Black Holes
Gibbons, G.W.; Perry, M.J.; Pope, C.N.
2005-12-02
We show that, if one chooses the Einstein static universe as the metric on the conformal boundary of Kerr-anti-de Sitter spacetime, then the Casimir energy of the boundary conformal field theory can easily be determined. The result is independent of the rotation parameters, and the total boundary energy then straightforwardly obeys the first law of thermodynamics. Other choices for the metric on the conformal boundary will give different, more complicated, results. As an application, we calculate the Casimir energy for free self-dual tensor multiplets in six dimensions and compare it with that of the seven-dimensional supergravity dual. They differ by a factor of 5/4.
The Hawking-Page crossover in noncommutative anti-deSitter space
NASA Astrophysics Data System (ADS)
Nicolini, Piero; Torrieri, Giorgio
2011-08-01
We study the problem of a Schwarzschild-anti-deSitter black hole in a non-commutative geometry framework, thought to be an effective description of quantum-gravitational spacetime. As a first step we derive the noncommutative geometry inspired Schwarzschild-anti-deSitter solution. After studying the horizon structure, we find that the curvature singularity is smeared out by the noncommutative fluctuations. On the thermodynamics side, we show that the black hole temperature, instead of a divergent behavior at small scales, admits a maximum value. This fact implies an extension of the Hawking-Page transition into a van der Waals-like phase diagram, with a critical point at a critical cosmological constant size in Plank units and a smooth crossover thereafter. We speculate that, in the gauge-string dictionary, this corresponds to the confinement "critical point" in number of colors at finite number of flavors, a highly non-trivial parameter that can be determined through lattice simulations.
Asymptotically (anti)-de Sitter solutions in Gauss-Bonnet gravity without a cosmological constant
Dehghani, M.H.
2004-09-15
In this paper I show that one can have asymptotically de Sitter, anti-de Sitter (AdS), and flat solutions in Gauss-Bonnet gravity without a cosmological constant term in field equations. First, I introduce static solutions whose three surfaces at fixed r and t have constant positive (k=1), negative (k=-1), or zero (k=0) curvature. I show that for k={+-}1 one can have asymptotically de Sitter, AdS, and flat spacetimes, while for the case of k=0, one has only asymptotically AdS solutions. Some of these solutions present naked singularities, while some others are black hole or topological black hole solutions. I also find that the geometrical mass of these five-dimensional spacetimes is m+2{alpha}|k|, which is different from the geometrical mass m of the solutions of Einstein gravity. This feature occurs only for the five-dimensional solutions, and is not repeated for the solutions of Gauss-Bonnet gravity in higher dimensions. Second, I add angular momentum to the static solutions with k=0, and introduce the asymptotically AdS charged rotating solutions of Gauss-Bonnet gravity. Finally, I introduce a class of solutions which yields an asymptotically AdS spacetime with a longitudinal magnetic field, which presents a naked singularity, and generalize it to the case of magnetic rotating solutions with two rotation parameters.
NASA Astrophysics Data System (ADS)
Yin, Shaoyu; Wang, Bin; Mann, Robert; Lee, Chong Oh; Lin, Chi-Yong; Su, Ru-Keng
2010-09-01
We investigate the stability of a new warped black string with nontrivial topologies in five-dimensional anti-de Sitter spacetime. After studying the linear gravitational perturbation, we find that this black string is unstable when the Kaluza-Klein mass falls in a certain range, and the instability exists for all topological spacetimes.
From the Anti-Yang Model to the Anti-Snyder Model and Anti-De Sitter Special Relativity
NASA Astrophysics Data System (ADS)
Qi, Wei-Jun; Ren, Xin-An
2013-04-01
Based on Yang's quantized space-time model, a complete Yang model from (5+1)-dimensional space with Minkowski signature is discussed using the projective geometry method and Dirac procedure. We introduce an anti-Yang model and an anti-Snyder model to discuss the duality relations between the anti-Snyder model and anti-de Sitter special relativity.
Reissner–Nordström Anti-de Sitter Black Holes in Mimetic F(R) Gravity
NASA Astrophysics Data System (ADS)
Oikonomou, V. K.
2016-05-01
In this paper we study under which conditions the Reissner-Nordstr\\"om-anti de Sitter black hole can be a solution of the vacuum mimetic $F(R)$ gravity with Lagrange multiplier and mimetic scalar potential. As we demonstrate, the resulting picture in the mimetic $F(R)$ gravity case, is different in comparison to the ordinary $F(R)$ gravity case, with the two descriptions resulting to a different set of constraints that need to hold true. We also investigate the metric perturbations in the mimetic $F(R)$ gravity case, for the Reissner-Nordstr\\"om-anti de Sitter black hole metric, at first order of the perturbed variables. Interestingly enough, the resulting equations are identical to the ones corresponding to the ordinary $F(R)$ gravity Reissner-Nordstr\\"om-anti de Sitter black hole, at least at first order. We attribute this feature to the particular form of the Reissner-Nordstr\\"om-anti de Sitter metric, and we speculate for which cases there could be differences between the mimetic and non-mimetic case. Since the perturbation equations are the same for the two cases, it is possible to have black hole instabilities in the mimetic $F(R)$ gravity case too, which can be interpreted as anti-evaporation of the black hole.
Strings in five-dimensional anti-de Sitter space with a symmetry
Koike, Tatsuhiko; Kozaki, Hiroshi; Ishihara, Hideki
2008-06-15
The equation of motion of an extended object in spacetime reduces to an ordinary differential equation in the presence of symmetry. By properly defining the symmetry with the notion of cohomogeneity, we discuss the method for classifying all these extended objects. We carry out the classification for the strings in the five-dimensional anti-de Sitter space by the effective use of the local isomorphism between SO(4,2) and SU(2,2). In the case where the string is described by the Nambu-Goto action, we present a general method for solving the trajectory. We then apply the method to one of the classification cases, where the spacetime naturally obtains a Hopf-like bundle structure, and find a solution. The geometry of the solution is analyzed and found to be a timelike, helicoidlike surface.
Nonlinear Evolution and Final Fate of Charged Anti-de Sitter Black Hole Superradiant Instability.
Bosch, Pablo; Green, Stephen R; Lehner, Luis
2016-04-01
We describe the full nonlinear development of the superradiant instability for a charged massless scalar field coupled to general relativity and electromagnetism, in the vicinity of a Reissner-Nordström-anti-de Sitter black hole. The presence of the negative cosmological constant provides a natural context for considering perfectly reflecting boundary conditions and studying the dynamics as the scalar field interacts repeatedly with the black hole. At early times, small superradiant perturbations grow as expected from linearized studies. Backreaction then causes the black hole to lose charge and mass until the perturbation becomes nonsuperradiant, with the final state described by a stable hairy black hole. For large gauge coupling, the instability extracts a large amount of charge per unit mass, resulting in greater entropy increase. We discuss the implications of the observed behavior for the general problem of superradiance in black hole spacetimes. PMID:27104693
Hawking evaporation time scale of topological black holes in anti-de Sitter spacetime
NASA Astrophysics Data System (ADS)
Ong, Yen Chin
2016-02-01
It was recently pointed out that if an absorbing boundary condition is imposed at infinity, an asymptotically anti-de Sitter Schwarzschild black hole with a spherical horizon takes only a finite amount of time to evaporate away even if its initial mass is arbitrarily large. We show that this is a rather generic property in AdS spacetimes: regardless of their horizon topologies, neutral AdS black holes in general relativity take about the same amount of time to evaporate down to the same size of order L, the AdS length scale. Our discussion focuses on the case in which the black hole has toral event horizon. A brief comment is made on the hyperbolic case, i.e. for black holes with negatively curved horizons.
Unique Continuation from Infinity in Asymptotically Anti-de Sitter Spacetimes
NASA Astrophysics Data System (ADS)
Holzegel, Gustav; Shao, Arick
2016-02-01
We consider the unique continuation properties of asymptotically anti-de Sitter spacetimes by studying Klein-Gordon-type equations {Box_g φ + σ φ = G ( φ, partial φ )} , {σ in R} , on a large class of such spacetimes. Our main result establishes that if {φ} vanishes to sufficiently high order (depending on {σ} ) on a sufficiently long time interval along the conformal boundary I, then the solution necessarily vanishes in a neighborhood of I. In particular, in the {σ} -range where Dirichlet and Neumann conditions are possible on I for the forward problem, we prove uniqueness if both these conditions are imposed. The length of the time interval can be related to the refocusing time of null geodesics on these backgrounds and is expected to be sharp. Some global applications as well as a uniqueness result for gravitational perturbations are also discussed. The proof is based on novel Carleman estimates established in this setting.
Collapse of Self-Interacting Scalar Field in Anti-de Sitter Space
NASA Astrophysics Data System (ADS)
Cai, Rong-Gen; Ji, Li-Wei; Yang, Run-Qiu
2016-03-01
The gravitational collapse of a massless scalar field with a self-interaction term λφ4 in anti-de Sitter space is investigated. We numerically investigate the effect of the self-interaction term on the critical amplitudes, forming time of apparent horizon, stable island, and energy transformation. The results show that a positive λ suppresses the formation of black hole, while a negative λ enhances the process. We define two susceptibilities to characterize the effect of the self-interaction on the black hole formation, and find that near the critical amplitude, there exists a universal scaling relation with the critical exponent α ≈ 0.74 for the time of black hole formation. Supported by the National Natural Science Foundation of China under Grant Nos. 11375247 and 11435006
Homoclinic accretion solutions in the Schwarzschild-anti-de Sitter space-time
NASA Astrophysics Data System (ADS)
Mach, Patryk
2015-04-01
The aim of this paper is to clarify the distinction between homoclinic and standard (global) Bondi-type accretion solutions in the Schwarzschild-anti-de Sitter space-time. The homoclinic solutions have recently been discovered numerically for polytropic equations of state. Here I show that they exist also for certain isothermal (linear) equations of state, and an analytic solution of this type is obtained. It is argued that the existence of such solutions is generic, although for sufficiently relativistic matter models (photon gas, ultrahard equation of state) there exist global solutions that can be continued to infinity, similarly to standard Michel's solutions in the Schwarzschild space-time. In contrast to that global solutions should not exist for matter models with a nonvanishing rest-mass component, and this is demonstrated for polytropes. For homoclinic isothermal solutions I derive an upper bound on the mass of the black hole for which stationary transonic accretion is allowed.
Charged anti-de Sitter scalar-tensor black holes and their thermodynamic phase structure
Doneva, Daniela D.; Yazadjiev, Stoytcho S.; Kokkotas, Kostas D.; Stefanov, Ivan Zh.; Todorov, Michail D.
2010-05-15
In the present paper we numerically construct new charged anti-de Sitter black holes coupled to nonlinear Born-Infeld electrodynamics within a certain class of scalar-tensor theories. The properties of the solutions are investigated both numerically and analytically. We also study the thermodynamics of the black holes in the canonical ensemble. For large values of the Born-Infeld parameter and for a certain interval of the charge values we find the existence of a first-order phase transition between small and very large black holes. An unexpected result is that for a certain small charge subinterval two phase transitions have been observed, one of zeroth and one of first order. It is important to note that such phase transitions are also observed for pure Einstein-Born-Infeld-AdS black holes.
Simulation of Black Hole Collisions in Asymptotically anti-de Sitter Spacetimes
NASA Astrophysics Data System (ADS)
Bantilan, Hans; Romatschke, Paul
2015-04-01
The main purpose of this talk is to describe, in detail, the necessary ingredients for achieving stable Cauchy evolution of black hole collisions in asymptotically anti-de Sitter (AdS) spacetimes. I will begin by motivating this program in terms of the heavy-ion physics it is intended to clarify. I will then give an overview of asymptotically AdS spacetimes, the mapping to the dual conformal field theory on the AdS boundary, and the method we use to numerically solve the fully non-linear Einstein field equations with AdS boundary conditions. As a concrete example of these ideas, I will describe the first proof of principle simulation of stable AdS black hole mergers in 5 dimensions.
Holographic thermalization, stability of anti-de sitter space, and the Fermi-Pasta-Ulam paradox.
Balasubramanian, Venkat; Buchel, Alex; Green, Stephen R; Lehner, Luis; Liebling, Steven L
2014-08-15
For a real massless scalar field in general relativity with a negative cosmological constant, we uncover a large class of spherically symmetric initial conditions that are close to anti-de Sitter space (AdS) but whose numerical evolution does not result in black hole formation. According to the AdS/conformal field theory (CFT) dictionary, these bulk solutions are dual to states of a strongly interacting boundary CFT that fail to thermalize at late times. Furthermore, as these states are not stationary, they define dynamical CFT configurations that do not equilibrate. We develop a two-time-scale perturbative formalism that captures both direct and inverse cascades of energy and agrees with our fully nonlinear evolutions in the appropriate regime. We also show that this formalism admits a large class of quasiperiodic solutions. Finally, we demonstrate a striking parallel between the dynamics of AdS and the classic Fermi-Pasta-Ulam-Tsingou problem. PMID:25170699
Nonlinear Evolution and Final Fate of Charged Anti-de Sitter Black Hole Superradiant Instability
NASA Astrophysics Data System (ADS)
Bosch, Pablo; Green, Stephen R.; Lehner, Luis
2016-04-01
We describe the full nonlinear development of the superradiant instability for a charged massless scalar field coupled to general relativity and electromagnetism, in the vicinity of a Reissner-Nordström-anti-de Sitter black hole. The presence of the negative cosmological constant provides a natural context for considering perfectly reflecting boundary conditions and studying the dynamics as the scalar field interacts repeatedly with the black hole. At early times, small superradiant perturbations grow as expected from linearized studies. Backreaction then causes the black hole to lose charge and mass until the perturbation becomes nonsuperradiant, with the final state described by a stable hairy black hole. For large gauge coupling, the instability extracts a large amount of charge per unit mass, resulting in greater entropy increase. We discuss the implications of the observed behavior for the general problem of superradiance in black hole spacetimes.
Anti-De Sitter Space, Thermal Phase Transition, and Confinement in Gauge Theories
NASA Astrophysics Data System (ADS)
Witten, Edward
2014-03-01
The correspondence between supergravity (and string theory) on AdS space and boundary conformal field theory relates the thermodynamics of N = 4 super Yang-Mills theory in four dimensions to the thermodynamics of Schwarzschild black holes in Anti-de Sitter space. In this description, quantum phenomena such as the spontaneous breaking of the center of the gauge group, magnetic confinement, and the mass gap are coded in classical geometry. The correspondence makes it manifest that the entropy of a very large AdS Schwarzschild black hole must scale "holographically" with the volume of its horizon. By similar methods, one can also make a speculative proposal for the description of large N gauge theories in four dimensions without supersymmetry.
Abundant stable gauge field hair for black holes in anti-de Sitter space.
Baxter, J E; Helbling, Marc; Winstanley, Elizabeth
2008-01-11
We present new hairy black hole solutions of SU(N) Einstein-Yang-Mills (EYM) theory in asymptotically anti-de Sitter (AdS) space. These black holes are described by N+1 independent parameters and have N-1 independent gauge field degrees of freedom. Solutions in which all gauge field functions have no zeros exist for all N, and for a sufficiently large (and negative) cosmological constant. At least some of these solutions are shown to be stable under classical, linear, spherically symmetric perturbations. Therefore there is no upper bound on the amount of stable gauge field hair with which a black hole in AdS can be endowed. PMID:18232751
New Features of Gravitational Collapse in Anti-de Sitter Spacetimes.
Santos-Oliván, Daniel; Sopuerta, Carlos F
2016-01-29
Gravitational collapse of a massless scalar field in spherically symmetric anti-de Sitter (AdS) spacetimes presents a new phenomenology with a series of critical points whose dynamics is discretely self-similar as in the asymptotically flat case. Each critical point is the limit of a branch of scalar field configurations that have bounced off the AdS boundary a fixed number of times before forming an apparent horizon. We present results from a numerical study that focus on the interfaces between branches. We find that there is a mass gap between branches and that subcritical configurations near the critical point form black holes with an apparent horizon mass that follows a power law of the form M(AH)-M(g)∝(p(c)-p)^(ξ), where M(g) is the mass gap and the exponent ξ≃0.7 appears to be universal. PMID:26871317
The Derivation and Quasinormal Mode Spectrum of Acoustic Anti-de Sitter Black Hole Analogues
NASA Astrophysics Data System (ADS)
Babb, James Patrick
Dumb holes (also known as acoustic black holes) are fluid flows which include an "acoustic horizon": a surface, analogous to a gravitational horizon, beyond which sound may pass but never classically return. Soundwaves in these flows will therefore experience "effective geometries" which are identical to black hole spacetimes up to a conformal factor. By adjusting the parameters of the fluid flow, it is possible to create an effective geometry which is conformal to the Anti-de Sitter black hole spacetime---a geometry which has received a great deal of attention in recent years due to its conjectured holographic duality to Conformal Field Theories. While we would not expect an acoustic analogue of the AdS-CFT correspondence to exist, this dumb hole provides a means, at least in principle, of experimentally testing the theoretical properties of the AdS spacetime. In particular, I have calculated the quasinormal mode spectrum of this acoustic geometry.
Conserved charges for gravity with locally anti-de sitter asymptotics
Aros; Contreras; Olea; Troncoso; Zanelli
2000-02-21
A new formula for the conserved charges in 3+1 gravity for spacetimes with local anti-de Sitter asymptotic geometry is proposed. It is shown that requiring the action to have an extremum for this class of asymptotia sets the boundary term that must be added to the Lagrangian as the Euler density with a fixed weight factor. The resulting action gives rise to the mass and angular momentum as Noether charges associated to the asymptotic Killing vectors without requiring specification of a reference background in order to have a convergent expression. A consequence of this definition is that any negative constant curvature spacetime has vanishing Noether charges. These results remain valid in the Lambda = 0 limit. PMID:11017591
New Features of Gravitational Collapse in Anti-de Sitter Spacetimes
NASA Astrophysics Data System (ADS)
Santos-Oliván, Daniel; Sopuerta, Carlos F.
2016-01-01
Gravitational collapse of a massless scalar field in spherically symmetric anti-de Sitter (AdS) spacetimes presents a new phenomenology with a series of critical points whose dynamics is discretely self-similar as in the asymptotically flat case. Each critical point is the limit of a branch of scalar field configurations that have bounced off the AdS boundary a fixed number of times before forming an apparent horizon. We present results from a numerical study that focus on the interfaces between branches. We find that there is a mass gap between branches and that subcritical configurations near the critical point form black holes with an apparent horizon mass that follows a power law of the form MAH-Mg∝(pc-p )ξ, where Mg is the mass gap and the exponent ξ ≃0.7 appears to be universal.
Quantum groups, roots of unity and particles on quantized Anti-de Sitter space
Steinacker, H
1997-05-23
Quantum groups in general and the quantum Anti-de Sitter group U{sub q}(so(2,3)) in particular are studied from the point of view of quantum field theory. The author shows that if q is a suitable root of unity, there exist finite-dimensional, unitary representations corresponding to essentially all the classical one-particle representations with (half) integer spin, with the same structure at low energies as in the classical case. In the massless case for spin {ge} 1, {open_quotes}naive{close_quotes} representations are unitarizable only after factoring out a subspace of {open_quotes}pure gauges{close_quotes}, as classically. Unitary many-particle representations are defined, with the correct classical limit. Furthermore, the author identifies a remarkable element Q in the center of U{sub q}(g), which plays the role of a BRST operator in the case of U{sub q}(so(2,3)) at roots of unity, for any spin {ge} 1. The associated ghosts are an intrinsic part of the indecomposable representations. The author shows how to define an involution on algebras of creation and anihilation operators at roots of unity, in an example corresponding to non-identical particles. It is shown how nonabelian gauge fields appear naturally in this framework, without having to define connections on fiber bundles. Integration on Quantum Euclidean space and sphere and on Anti-de Sitter space is studied as well. The author gives a conjecture how Q can be used in general to analyze the structure of indecomposable representations, and to define a new, completely reducible associative (tensor) product of representations at roots of unity, which generalizes the standard {open_quotes}truncated{close_quotes} tensor product as well as many-particle representations.
Vacuum for a massless quantum scalar field outside a collapsing shell in anti-de Sitter space-time
NASA Astrophysics Data System (ADS)
Abel, Paul G.; Winstanley, Elizabeth
2016-08-01
We consider a massless quantum scalar field on a two-dimensional space-time describing a thin shell of matter collapsing to form a Schwarzschild-anti-de Sitter black hole. At early times, before the shell starts to collapse, the quantum field is in the vacuum state, corresponding to the Boulware vacuum on an eternal black hole space-time. The scalar field satisfies reflecting boundary conditions on the anti-de Sitter boundary. Using the Davies-Fulling-Unruh prescription for computing the renormalized expectation value of the stress-energy tensor, we find that at late times the black hole is in thermal equilibrium with a heat bath at the Hawking temperature, so the quantum field is in a state analogous to the Hartle-Hawking vacuum on an eternal black hole space-time.
NASA Astrophysics Data System (ADS)
Vasudevan, Muraari; Stevens, Kory A.
2005-12-01
We study the Hamilton-Jacobi and massive Klein-Gordon equations in the general Kerr-(Anti) de Sitter black hole background in all dimensions. Complete separation of both equations is carried out in cases when there are two sets of equal black hole rotation parameters. We analyze explicitly the symmetry properties of these backgrounds that allow for this Liouville integrability and construct a nontrivial irreducible Killing tensor associated with the enlarged symmetry group which permits separation. We also derive first-order equations of motion for particles in these backgrounds and examine some of their properties. This work greatly generalizes previously known results for both the Myers-Perry metrics, and the Kerr-(Anti) de Sitter metrics in higher dimensions.
Gibbons, G. W.; Perry, M. J.; Pope, C. N.
2006-10-15
We reformulate the Bekenstein bound as the requirement of positivity of the Helmholtz free energy at the minimum value of the function L=E-S/(2{pi}R), where R is some measure of the size of the system. The minimum of L occurs at the temperature T=1/(2{pi}R). In the case of n-dimensional anti-de Sitter spacetime, the rather poorly defined size R acquires a precise definition in terms of the AdS radius l, with R=l/(n-2). We previously found that the Bekenstein bound holds for all known black holes in AdS. However, in this paper we show that the Bekenstein bound is not generally valid for free quantum fields in AdS, even if one includes the Casimir energy. Some other aspects of thermodynamics in anti-de Sitter spacetime are briefly touched upon.
NASA Astrophysics Data System (ADS)
Lin, Kai; Yang, ShuZheng
2009-04-01
The 1/2 spin fermions tunneling at the horizon of n-dimensional Kerr-Anti-de Sitter black hole with one rotational parameter is researched via semi-classical approximation method, and the Hawking temperature and fermions tunneling rate are obtained in this Letter. Using a new method, the semi-classical Hamilton-Jacobi equation is gotten from the Dirac equation in this Letter, and the work makes several quantum tunneling theories more harmonious.
Black hole formation from pointlike particles in three-dimensional anti-de Sitter space
NASA Astrophysics Data System (ADS)
Lindgren, E. J.
2016-07-01
We study collisions of many point-like particles in three-dimensional anti-de Sitter space, generalizing the known result with two particles. We show how to construct exact solutions corresponding to the formation of either a black hole or a conical singularity from the collision of an arbitrary number of massless particles falling in radially from the boundary. We find that when going away from the case of equal energies and discrete rotational symmetry, this is not a trivial generalization of the two-particle case, but requires that the excised wedges corresponding to the particles must be chosen in a very precise way for a consistent solution. We also explicitly take the limit when the number of particles goes to infinity and obtain thin shell solutions that in general break rotational invariance, corresponding to an instantaneous and inhomogeneous perturbation at the boundary. We also compute the stress–energy tensor of the shell using the junction formalism for null shells and obtain agreement with the point particle picture.
Conserved quantities and dual turbulent cascades in Anti-de Sitter spacetime
NASA Astrophysics Data System (ADS)
Green, Stephen; Buchel, Alex; Lehner, Luis; Liebling, Steven
2015-04-01
We consider the dynamics of a spherically symmetric massless scalar field coupled to general relativity in Anti-de Sitter spacetime in the small-amplitude limit. Within the context of our previously developed two time framework (TTF) to study the leading self-gravitating effects, we demonstrate the existence of two new conserved quantities in addition to the known total energy E of the modes: The particle number N and Hamiltonian H of our TTF system. H represents the next-order contribution after E to the total ADM mass M. Simultaneous conservation of E and N implies that weak turbulent processes undergo dual cascades (direct cascade of E and inverse cascade of N or vice versa). This partially explains the observed dynamics of 2-mode initial data. In addition, conservation of E and N limits the region of phase space that can be explored within the TTF approximation and in particular rules out equipartion of energy among the modes for general initial data. Finally, we discuss possible effects of conservation of N and E on late time dynamics.
Conserved quantities and dual turbulent cascades in anti-de Sitter spacetime
NASA Astrophysics Data System (ADS)
Buchel, Alex; Green, Stephen R.; Lehner, Luis; Liebling, Steven L.
2015-03-01
We consider the dynamics of a spherically symmetric massless scalar field coupled to general relativity in anti-de Sitter spacetime in the small-amplitude limit. Within the context of our previously developed two time framework (TTF) to study the leading self-gravitating effects, we demonstrate the existence of two new conserved quantities in addition to the known total energy E of the modes: The particle number N and Hamiltonian H of our TTF system. Simultaneous conservation of E and N implies that weakly turbulent processes undergo dual cascades (direct cascade of E and inverse cascade of N or vice versa). This partially explains the observed dynamics of 2-mode initial data. In addition, conservation of E and N limits the region of phase space that can be explored within the TTF approximation and, in particular, rules out equipartition of energy among the modes for general initial data. Finally, we discuss the possible effects of conservation of N and E on late time dynamics.
Precise relativistic orbits in Kerr and Kerr (anti) de Sitter spacetimes
NASA Astrophysics Data System (ADS)
Kraniotis, G. V.
2004-10-01
The timelike geodesic equations resulting from the Kerr gravitational metric element are derived and solved exactly including the contribution from the cosmological constant. The geodesic equations are derived, by solving the Hamilton Jacobi partial differential equation by separation of variables. The solutions can be applied in the investigation of the motion of a test particle in the Kerr and Kerr (anti) de Sitter gravitational fields. In particular, we apply the exact solutions of the timelike geodesics: (i) to the precise calculation of dragging (Lense Thirring effect) of a satellite's spherical polar orbit in the gravitational field of Earth assuming Kerr geometry; (ii) assuming the galactic centre is a rotating black hole we calculate the precise dragging of a stellar polar orbit around the galactic centre for various values of the Kerr parameter including those supported by recent observations. The exact solution of non-spherical geodesics in Kerr geometry is obtained by using the transformation theory of elliptic functions. The exact solution of spherical polar geodesics with a nonzero cosmological constant can be expressed in terms of Abelian modular theta functions that solve the corresponding Jacobi's inversion problem.
Scalar hair on the black hole in asymptotically anti--de Sitter spacetime
Torii, Takashi; Maeda, Kengo; Narita, Makoto
2001-08-15
We examine the no-hair conjecture in asymptotically anti--de Sitter (AdS) spacetime. First, we consider a real scalar field as the matter field and assume static spherically symmetric spacetime. Analysis of the asymptotics shows that the scalar field must approach the extremum of its potential. Using this fact, it is proved that there is no regular black hole solution when the scalar field is massless or has a 'convex' potential. Surprisingly, while the scalar field has a growing mode around the local minimum of the potential, there is no growing mode around the local maximum. This implies that the local maximum is a kind of 'attractor' of the asymptotic scalar field. We give two examples of the new black hole solutions with a nontrivial scalar field configuration numerically in the symmetric or asymmetric double well potential models. We study the stability of these solutions by using the linear perturbation method in order to examine whether or not the scalar hair is physical. In the symmetric double well potential model, we find that the potential function of the perturbation equation is positive semidefinite in some wide parameter range and that the new solution is stable. This implies that the black hole no-hair conjecture is violated in asymptotically AdS spacetime.
Globally regular instability of 3-dimensional anti-de Sitter spacetime.
Bizoń, Piotr; Jałmużna, Joanna
2013-07-26
We consider three-dimensional anti-de Sitter (AdS) gravity minimally coupled to a massless scalar field and study numerically the evolution of small smooth circularly symmetric perturbations of the AdS3 spacetime. As in higher dimensions, for a large class of perturbations, we observe a turbulent cascade of energy to high frequencies which entails instability of AdS3. However, in contrast to higher dimensions, the cascade cannot be terminated by black hole formation because small perturbations have energy below the black hole threshold. This situation appears to be challenging for the cosmic censor. Analyzing the energy spectrum of the cascade we determine the width ρ(t) of the analyticity strip of solutions in the complex spatial plane and argue by extrapolation that ρ(t) does not vanish in finite time. This provides evidence that the turbulence is too weak to produce a naked singularity and the solutions remain globally regular in time, in accordance with the cosmic censorship hypothesis. PMID:23931347
Quasinormal modes of (anti-)de Sitter black holes in the 1 /D expansion
NASA Astrophysics Data System (ADS)
Emparan, Roberto; Suzuki, Ryotaku; Tanabe, Kentaro
2015-04-01
We use the inverse-dimensional expansion to compute analytically the frequencies of a set of quasinormal modes of static black holes of Einstein-(Anti-)de Sitter gravity, including the cases of spherical, planar or hyperbolic horizons. The modes we study are decoupled modes localized in the near-horizon region, which are the ones that capture physics peculiar to each black hole (such as their instabilities), and which in large black holes contain hydrodynamic behavior. Our results also give the unstable Gregory-Laflamme frequencies of Ricci-flat black branes to two orders higher in 1 /D than previous calculations. We discuss the limits on the accuracy of these results due to the asymptotic but not convergent character of the 1 /D expansion, which is due to the violation of the decoupling condition at finite D. Finally, we compare the frequencies for AdS black branes to calculations in the hydrodynamic expansion in powers of the momentum k. Our results extend up to k 9 for the sound mode and to k 8 for the shear mode.
Spherical and planar three-dimensional anti-de Sitter black holes
NASA Astrophysics Data System (ADS)
Zanchin, Vilson T.; Miranda, Alex S.
2004-02-01
The technique of dimensional reduction was used in a recent paper (Zanchin V T, Kleber A and Lemos J P S 2002 Phys. Rev. D 66 064022) where a three-dimensional (3D) Einstein Maxwell dilaton theory was built from the usual four-dimensional (4D) Einstein Maxwell Hilbert action for general relativity. Starting from a class of 4D toroidal black holes in asymptotically anti-de Sitter (AdS) spacetimes several 3D black holes were obtained and studied in such a context. In the present work we choose a particular case of the 3D action which presents Maxwell field, dilaton field and an extra scalar field, besides gravity field and a negative cosmological constant, and obtain new 3D static black hole solutions whose horizons may have spherical or planar topology. We show that there is a 3D static spherically symmetric solution analogous to the 4D Reissner Nordström AdS black hole, and obtain other new 3D black holes with planar topology. From the static spherical solutions, new rotating 3D black holes are also obtained and analysed in some detail.
NASA Astrophysics Data System (ADS)
Peng, Jun-Jin; Wu, Shuang-Qing
2008-03-01
Motivated by the success of the recently proposed method of anomaly cancellation to derive Hawking fluxes from black hole horizons of spacetimes in various dimensions, we have further extended the covariant anomaly cancellation method shortly simplified by Banerjee and Kulkarni to explore the Hawking radiation of the (3 + 1)-dimensional charged rotating black strings and their higher dimensional extensions in anti-de Sitter spacetimes, whose horizons are not spherical but can be toroidal, cylindrical or planar, according to their global identifications. It should be emphasized that our analysis presented here is very general in the sense that the determinant of the reduced (1 + 1)-dimensional effective metric from these black strings need not be equal to one (√{ - g } ≠ 1). Our results indicate that the gauge and energy-momentum fluxes needed to cancel the (1 + 1)-dimensional covariant gauge and gravitational anomalies are compatible with the Hawking fluxes. Besides, thermodynamics of these black strings are studied in the case of a variable cosmological constant.
Rainbow valley of colored (anti) de Sitter gravity in three dimensions
NASA Astrophysics Data System (ADS)
Gwak, Seungho; Joung, Euihun; Mkrtchyan, Karapet; Rey, Soo-Jong
2016-04-01
We propose a theory of three-dimensional (anti) de Sitter gravity carrying Chan-Paton color charges. We define the theory by Chern-Simons formulation with the gauge algebra (gl_2oplus gl_2)⊗ u(N) , obtaining a color-decorated version of interacting spin-one and spin-two fields. We also describe the theory in metric formulation and show that, among N 2 massless spin-two fields, only the singlet one plays the role of metric graviton whereas the rest behave as colored spinning matter that strongly interacts at large N. Remarkably, these colored spinning matter acts as Higgs field and generates a non-trivial potential of staircase shape. At each extremum labelled by k=0,dots, [N-1/2] , the u(N) color gauge symmetry is spontaneously broken down to u(N-k)oplus u(k) and provides different (A)dS backgrounds with the cosmological constants {(N/N-2k)}^2Λ . When this symmetry breaking takes place, the spin-two Goldstone modes combine with (or are eaten by) the spin-one gauge fields to become partially-massless spin-two fields. We discuss various aspects of this theory and highlight physical implications.
Miranda, Alex S.; Zanchin, Vilson T.
2006-03-15
We study in detail the quasinormal modes of linear gravitational perturbations of plane-symmetric anti-de Sitter black holes. The wave equations are obtained by means of the Newman-Penrose formalism and the Chandrasekhar transformation theory. We show that oscillatory modes decay exponentially with time such that these black holes are stable against gravitational perturbations. Our numerical results show that in the large (small) black hole regime the frequencies of the ordinary quasinormal modes are proportional to the horizon radius r{sub +} (wave number k). The frequency of the purely damped mode is very close to the algebraically special frequency in the small horizon limit, and goes as ik{sup 2}/3r{sub +} in the opposite limit. This result is confirmed by an analytical method based on the power series expansion of the frequency in terms of the horizon radius. The same procedure applied to the Schwarzschild anti-de Sitter spacetime proves that the purely damped frequency goes as i(l-1)(l+2)/3r{sub +}, where l is the quantum number characterizing the angular distribution. Finally, we study the limit of high overtones and find that the frequencies become evenly spaced in this regime. The spacing of the frequency per unit horizon radius seems to be a universal quantity, in the sense that it is independent of the wave number, perturbation parity, and black hole size.
Test of the Anti-de Sitter-Space/Conformal-Field-Theory Correspondence Using High-Spin Operators
Benna, M. K.; Benvenuti, S.; Klebanov, I. R.; Scardicchio, A.
2007-03-30
In two remarkable recent papers the planar perturbative expansion was proposed for the universal function of the coupling appearing in the dimensions of high-spin operators of the N=4 super Yang-Mills theory. We study numerically the integral equation derived by Beisert, Eden, and Staudacher, which resums the perturbative series. In a confirmation of the anti-de Sitter-space/conformal-field-theory (AdS/CFT) correspondence, we find a smooth function whose two leading terms at strong coupling match the results obtained for the semiclassical folded string spinning in AdS{sub 5}. We also make a numerical prediction for the third term in the strong coupling series.
Quasinormal modes of black holes in anti-de Sitter space: A numerical study of the eikonal limit
Morgan, Jaqueline; Zanchin, Vilson T.; Cardoso, Vitor; Miranda, Alex S.; Molina, C.
2009-07-15
Using series solutions and time-domain evolutions, we probe the eikonal limit of the gravitational and scalar-field quasinormal modes of large black holes and black branes in anti-de Sitter backgrounds. These results are particularly relevant for the AdS/CFT correspondence, since the eikonal regime is characterized by the existence of long-lived modes which (presumably) dominate the decay time scale of the perturbations. We confirm all the main qualitative features of these slowly damped modes as predicted by Festuccia and Liu [G. Festuccia and H. Liu, arXiv:0811.1033.] for the scalar-field (tensor-type gravitational) fluctuations. However, quantitatively we find dimensional-dependent correction factors. We also investigate the dependence of the quasinormal mode frequencies on the horizon radius of the black hole (brane) and the angular momentum (wave number) of vector- and scalar-type gravitational perturbations.
Quasilocal thermodynamics of Kerr and Kerr--anti-de Sitter spacetimes and the AdS/CFT correspondence
Dehghani, M. H.; Mann, R. B.
2001-08-15
We consider the quasilocal thermodynamics of rotating black holes in asymptotically flat and asymptotically anti--de Sitter (AdS) spacetimes. Using the minimal number of intrinsic boundary counterterms inspired by the AdS/conformal field theory correspondence, we find that we are able to carry out an analysis of the thermodynamics of these black holes for virtually all possible values of the rotation parameter and cosmological constant that leave the quasilocal boundary well defined, going well beyond what is possible with background subtraction methods. Specifically, we compute the quasilocal energy E and angular momentum J for arbitrary values of the rotation, mass, and cosmological constant parameters for the (3+1)-dimensional Kerr, Kerr-AdS black holes, and (2+1)-dimensional Banados-Teitelboim-Zannelli (BTZ) black hole. We perform a quasilocal stability analysis and find phase behavior that is commensurate with previous analyses carried out at infinity.
NASA Astrophysics Data System (ADS)
Santos-Oliván, Daniel; Sopuerta, Carlos F.
2016-05-01
We present a new hybrid Cauchy-characteristic evolution scheme that is particularly suited to study gravitational collapse in spherically symmetric asymptotically (global) anti-de Sitter (AdS) spacetimes. The Cauchy evolution allows us to track the scalar field through the different round trips to the AdS boundary, while the characteristic method can bring us very close to the point of formation of an apparent horizon. We describe all the details of the method, including the transition between the two evolution schemes and the details of the numerical implementation for the case of massless scalar fields. We use this scheme to provide more numerical evidence for a recent conjecture on the power law scaling of the apparent horizon mass resulting from the collapse of subcritical configurations. We also compute the critical exponents and echoing periods for a number of critical points and confirm the expectation that their values should be the same as in the asymptotically flat case.
NASA Astrophysics Data System (ADS)
Lin, Kai; Yang, ShuZheng
2009-10-01
Applying the method beyond semiclassical approximation, fermion tunneling from higher-dimensional anti-de Sitter Schwarzschild black hole is researched. In our work, the "tortoise" coordinate transformation is introduced to simplify Dirac equation, so that the equation proves that only the (r - t) sector is important to our research. Because we only need to study the (r - t) sector, the Dirac equation is decomposed into several pairs of equations spontaneously, and we then prove the components of wave functions are proportional to each other in every pair of equations. Therefore, the suitable action forms of the wave functions are obtained, and finally the correctional Hawking temperature and entropy can be determined via the method beyond semiclassical approximation.
NASA Astrophysics Data System (ADS)
Li, Ran; Zhao, Jun-Kun
2016-04-01
We investigate the massive vector particles' Hawking radiation from the neutral rotating Anti-de Sitter (AdS) black holes in conformal gravity by using the tunneling method. It is well known that the dynamics of massive vector particles are governed by the Proca field equation. Applying WKB approximation to the Proca equation, the tunneling probabilities and radiation spectrums of the emitted particles are derived. Hawking temperature of the neutral rotating AdS black holes in conformal gravity is recovered, which is consistent with the previous result in the literature. Supported by the National Natural Science Foundation of China under Grant No. 11205048, and the Foundation for Young Key Teacher of Henan Normal University
NASA Astrophysics Data System (ADS)
Rahman, M. Atiqur; Hossain, M. Ilias
2013-06-01
The massive particles tunneling method has been used to investigate the Hawking non-thermal and purely thermal radiations of Schwarzschild Anti-de Sitter (SAdS) black hole. Considering the spacetime background to be dynamical, incorporate the self-gravitation effect of the emitted particles the imaginary part of the action has been derived from Hamilton-Jacobi equation. Using the conservation laws of energy and angular momentum we have showed that the non-thermal and purely thermal tunneling rates are related to the change of Bekenstein-Hawking entropy and the derived emission spectrum deviates from the pure thermal spectrum. The result obtained for SAdS black hole is also in accordance with Parikh and Wilczek's opinion and gives a correction to the Hawking radiation of SAdS black hole.
Maeda, Kengo; Fujii, Shunsuke; Koga, Jun-ichirou
2010-06-15
We investigate instability of four-dimensional Reissner-Nordstroem-anti-de Sitter (RN-AdS{sub 4}) black holes with various topologies by charged scalar field perturbations. We numerically find that the RN-AdS{sub 4} black holes become unstable against the linear perturbations below a critical temperature. It is analytically shown that charge extraction from the black holes occurs during the unstable evolution. To explore the end state of the instability, we perturbatively construct static black hole solutions with the scalar hair near the critical temperature. It is numerically found that the entropy of the hairy black hole is always larger than the one of the unstable RN-AdS{sub 4} black hole in the microcanonical ensemble. Our results support the speculation that the black hole with charged scalar hair always appears as the final fate of the instability of the RN-AdS{sub 4} black hole.
NASA Astrophysics Data System (ADS)
Wu, Shuang-Qing
2009-03-01
It is shown that the Dirac equation is separable by variables in a five-dimensional rotating Kerr (anti-)de Sitter black hole with two independent angular momenta. A first-order symmetry operator that commutes with the Dirac operator is constructed in terms of a rank-3 Killing Yano tensor whose square is a second-order symmetric Stäckel Killing tensor admitted by the five-dimensional Kerr (anti-)de Sitter spacetime. We highlight the construction procedure of such a symmetry operator. In addition, the first law of black hole thermodynamics has been extended to the case that the cosmological constant can be viewed as a thermodynamical variable.
NASA Astrophysics Data System (ADS)
Madriz Aguilar, José Edgar
2007-02-01
In this Letter we study the generation of gravitational waves during inflation from a 5D vacuum theory of gravity. Within this formalism, on an effective 4D de Sitter background, we recover the typical results obtained with 4D inflationary theory in general relativity, for the amplitude of gravitational waves generated during inflation. We also obtain a range of values for the amplitude of tensor to scalar ratio which is in agreement with COBE observations.
Dirac equation for massive neutrinos in a Schwarzschild-de Sitter spacetime from a 5D vacuum
NASA Astrophysics Data System (ADS)
Sánchez, Pablo Alejandro; Anabitarte, Mariano; Bellini, Mauricio
2011-11-01
Starting from a Dirac equation for massless neutrino in a 5D Ricci-flat background metric, we obtain the effective 4D equation for massive neutrino in a Schwarzschild-de Sitter (SdS) background metric from an extended SdS 5D Ricci-flat metric. We use the fact that the spin connection is defined to an accuracy of a vector, so that the covariant derivative of the spinor field is strongly dependent of the background geometry. We show that the mass of the neutrino can be induced from the extra space-like dimension.
NASA Astrophysics Data System (ADS)
Wang, Mengjie; Herdeiro, Carlos; Sampaio, Marco O. P.
2015-12-01
Perturbations of asymptotically anti-de-Sitter (AdS) spacetimes are often considered by imposing field vanishing boundary conditions (BCs) at the AdS boundary. Such BCs, of Dirichlet-type, imply a vanishing energy flux at the boundary, but the converse is, generically, not true. Regarding AdS as a gravitational box, we consider vanishing energy flux (VEF) BCs as a more fundamental physical requirement and we show that these BCs can lead to a new branch of modes. As a concrete example, we consider Maxwell perturbations on Kerr-AdS black holes in the Teukolsky formalism, but our formulation applies also for other spin fields. Imposing VEF BCs, we find a set of two Robin BCs, even for Schwarzschild-AdS black holes. The Robin BCs on the Teukolsky variables can be used to study quasinormal modes, superradiant instabilities and vector clouds. As a first application, we consider here the quasinormal modes of Schwarzschild-AdS black holes. We find that one of the Robin BCs yields the quasinormal spectrum reported in the literature, while the other one unveils a new branch for the quasinormal spectrum.
NASA Astrophysics Data System (ADS)
Wang, Mengjie; Herdeiro, Carlos
2016-03-01
Scalar and gravitational perturbations on Kerr-anti-de Sitter (Kerr-AdS) black holes have been addressed in the literature and have been shown to exhibit a rich phenomenology. In this paper, we complete the analysis of bosonic fields on this background by studying Maxwell perturbations, focusing on superradiant instabilities and vector clouds. For this purpose, we solve the Teukolsky equations numerically, imposing the boundary conditions we have proposed in [1] for the radial Teukolsky equation. As found therein, two Robin boundary conditions can be imposed for Maxwell fields on Kerr-AdS black holes, one of which produces a new set of quasinormal modes even for Schwarzschild-AdS black holes. Here, we show these different boundary conditions produce two different sets of superradiant modes. Interestingly, the "new modes" may be unstable in a larger parameter space. We then study stationary Maxwell clouds that exist at the threshold of the superradiant instability, with the two Robin boundary conditions. These clouds, obtained at the linear level, indicate the existence of a new family of black hole solutions at the nonlinear level, within the Einstein-Maxwell-AdS system, branching off from the Kerr-Newman-AdS family. As a comparison with the Maxwell clouds, scalar clouds on Kerr-AdS black holes are also studied, and it is shown there are Kerr-AdS black holes that are stable against scalar, but not vector, modes with the same "quantum numbers".
Stability of Gauss-Bonnet black holes in anti-de Sitter space-time against scalar field condensation
Brihaye, Yves; Hartmann, Betti
2011-10-15
We study the stability of static, hyperbolic Gauss-Bonnet black holes in (4+1)-dimensional anti-de Sitter (AdS) space-time against the formation of scalar hair. Close to extremality the black holes possess a near-horizon topology of AdS{sub 2}xH{sup 3} such that within a certain range of the scalar field mass one would expect that they become unstable to the condensation of an uncharged scalar field. We confirm this numerically and observe that there exists a family of hairy black hole solutions labeled by the number of nodes of the scalar field function. We construct explicit examples of solutions with a scalar field that possesses zero nodes, one node, and two nodes, respectively, and show that the solutions with nodes persist in the limit of Einstein gravity, i.e. for vanishing Gauss-Bonnet coupling. We observe that the interval of the mass for which scalar field condensation appears decreases with increasing Gauss-Bonnet coupling and/or with increasing node number.
Dyons and dyonic black holes in su (N ) Einstein-Yang-Mills theory in anti-de Sitter spacetime
NASA Astrophysics Data System (ADS)
Shepherd, Ben L.; Winstanley, Elizabeth
2016-03-01
We present new spherically symmetric, dyonic soliton and black hole solutions of the su (N ) Einstein-Yang-Mills equations in four-dimensional asymptotically anti-de Sitter spacetime. The gauge field has nontrivial electric and magnetic components and is described by N -1 magnetic gauge field functions and N -1 electric gauge field functions. We explore the phase space of solutions in detail for su (2 ) and su (3 ) gauge groups. Combinations of the electric gauge field functions are monotonic and have no zeros; in general the magnetic gauge field functions may have zeros. The phase space of solutions is extremely rich, and we find solutions in which the magnetic gauge field functions have more than fifty zeros. Of particular interest are solutions for which the magnetic gauge field functions have no zeros, which exist when the negative cosmological constant has sufficiently large magnitude. We conjecture that at least some of these nodeless solutions may be stable under linear, spherically symmetric, perturbations.
NASA Astrophysics Data System (ADS)
Ghosh, Shubhrangshu; Banik, Prabir
2015-07-01
In this paper, we present a complete work on steady state spherically symmetric Bondi type accretion flow in the presence of cosmological constant (Λ) in both Schwarzschild-de Sitter (SDS) and Schwarzschild anti-de Sitter (SADS) backgrounds considering an isolated supermassive black hole (SMBH), with the inclusion of a simple radiative transfer scheme, in the pseudo-general relativistic paradigm. We do an extensive analysis on the transonic behavior of the Bondi type accretion flow onto the cosmological BHs including a complete analysis of the global parameter space and the stability of flow, and do a complete study of the global family of solutions for a generic polytropic flow. Bondi type accretion flow in SADS background renders multiplicity in its transonic behavior with inner "saddle" type and outer "center" type sonic points, with the transonic solutions forming closed loops or contours. There is always a limiting value for ∣Λ∣ up to which we obtain valid stationary transonic solutions, which correspond to both SDS and SADS geometries; this limiting value moderately increases with the increasing radiative efficiency of the flow, especially correspond to Bondi type accretion flow in SADS background. Repulsive Λ suppresses the Bondi accretion rate by an order of magnitude for relativistic Bondi type accretion flow for a certain range in temperature, and with a marginal increase in the Bondi accretion rate if the corresponding accretion flow occurs in SADS background. However, for a strongly radiative Bondi type accretion flow with high mass accretion rate, the presence of cosmological constant do not much influence the corresponding Bondi accretion rate of the flow. Our analysis show that the relic cosmological constant has a substantial effect on Bondi type accretion flow onto isolated SMBHs and their transonic solutions beyond length-scale of kiloparsecs, especially if the Bondi type accretion occurs onto the host supergiant ellipticals or central
Randall-Sundrum membrane model with 7D anti-de Sitter space
Bao, Ruoyu; Lykken, Joseph D.; /Chicago U., EFI /Chicago U. /Fermilab
2005-09-01
In the same sense that AdS{sub 5} warped geometries arise naturally from Type IIB string theory with stacks of D3 branes, AdS{sub 7} warped geometries arise naturally from M theory with stacks of M5 branes. We compactify two spatial dimensions of AdS{sub 7} to get AdS{sub 5} x {Sigma}{sup 2}, where {Sigma}{sup 2} is e.g. a torus T{sup 2} or a sphere S{sup 2}. The metric for {Sigma} inherits the same warp factor as appears in the AdS{sub 5}. Bulk fields generically have both Kaluza-Klein and winding modes associated with {Sigma}. In the effective 5d action these will contribute exotic new excitations. We analyze the 5d spectrum in detail for the case of a bulk scalar or a graviton in AdS{sub 5} x T{sup 2}, in a setup which mimics the first Randall-Sundrum model. The results display several novel features, some of which might be observed in experiments at the LHC. For example, we obtain TeV scale string winding states without lowering the string scale. This is due to the double warping which is a generic feature of winding states along compactified AdS directions. Experimental verification of these signatures of AdS{sub 7} could be interpreted as direct evidence for M theory.
Uchikata, Nami; Yoshida, Shijun
2011-03-15
We investigate quasinormal modes of a massless charged scalar field on a small Reissner-Nordstroem-anti-de Sitter (RN-AdS) black hole both with analytical and numerical approaches. In the analytical approach, by using the small black hole approximation (r{sub +}<
Berenstein, David; Correa, Diego H.; Vazquez, Samuel E.
2005-11-04
We study an XXX open spin chain with variable number of sites, where the variability is introduced only at the boundaries. This model arises naturally in the study of giant gravitons in the anti-de Sitter-space/conformal field-theory correspondence. We show how to quantize the spin chain by mapping its states to a bosonic lattice of finite length with sources and sinks of particles at the boundaries. Using coherent states, we show how the Hamiltonian for the bosonic lattice gives the correct description of semiclassical open strings ending on giant gravitons.
NASA Astrophysics Data System (ADS)
Mehdipour, S. Hamid
2014-09-01
We try to study the thermodynamical features of a non-commutative inspired Schwarzschild-anti-de Sitter black hole in the context of the entropic gravity model, particularly for the model that is employed in a broad range of scales, from the short distances to the large distances. At small length scales, the Newtonian force fails because one finds a linear relation between the entropic force and the distance. In addition, there are some deviations from the standard Newtonian gravity at large length scales.
Natural inflation in 5D warped backgrounds
NASA Astrophysics Data System (ADS)
González Felipe, R.; Santos, N. M. C.
2008-07-01
In light of the five-year data from the Wilkinson Microwave Anisotropy Probe (WMAP), we discuss models of inflation based on the pseudo Nambu-Goldstone potential predicted in five-dimensional gauge theories for different backgrounds: flat Minkowski, anti de Sitter, and dilatonic spacetime. In this framework, the inflaton potential is naturally flat due to shift symmetries and the mass scales associated with it are related to 5D geometrical quantities.
Noronha, Jorge; Gyulassy, Miklos; Torrieri, Giorgio
2009-03-13
We show that far zone Mach and diffusion wake 'holograms' produced by supersonic strings in anti-de Sitter space/conformal field theory (AdS/CFT) correspondence do not lead to observable conical angular correlations in the strict N{sub c}{yields}{infinity} supergravity limit if Cooper-Frye hadronization is assumed. However, a special nonequilibrium 'neck' zone near the jet is shown to produce an apparent sonic boom azimuthal angle distribution that is roughly independent of the heavy quark's velocity. Our results indicate that a measurement of the dependence of the away-side correlations on the velocity of associated identified heavy quark jets at the BNL Relativistic Heavy Ion Collider and CERN LHC will provide a direct test of the nonperturbative dynamics involved in the coupling between jets and the strongly coupled quark-gluon plasma implied by AdS/CFT correspondence.
Noronha, Jorge; Gyulassy, Miklos; Torrieri, Giorgio
2009-03-13
We show that far zone Mach and diffusion wake "holograms" produced by supersonic strings in anti-de Sitter space/conformal field theory (AdS/CFT) correspondence do not lead to observable conical angular correlations in the strict N_{c}-->infinity supergravity limit if Cooper-Frye hadronization is assumed. However, a special nonequilibrium "neck" zone near the jet is shown to produce an apparent sonic boom azimuthal angle distribution that is roughly independent of the heavy quark's velocity. Our results indicate that a measurement of the dependence of the away-side correlations on the velocity of associated identified heavy quark jets at the BNL Relativistic Heavy Ion Collider and CERN LHC will provide a direct test of the nonperturbative dynamics involved in the coupling between jets and the strongly coupled quark-gluon plasma implied by AdS/CFT correspondence. PMID:19392107
NASA Astrophysics Data System (ADS)
Ilias Hossain, M.; Atiqur Rahman, M.
2013-09-01
We have investigated Hawking non-thermal and purely thermal Radiations of Reissner Nordström anti-de Sitter (RNAdS) black hole by massive particles tunneling method. The spacetime background has taken as dynamical, incorporate the self-gravitation effect of the emitted particles the imaginary part of the action has derived from Hamilton-Jacobi equation. We have supposed that energy and angular momentum are conserved and have shown that the non-thermal and thermal tunneling rates are related to the change of Bekenstein-Hawking entropy and the derived emission spectrum deviates from the pure thermal spectrum. The results for RNAdS black hole is also in the same manner with Parikh and Wilczek's opinion and explored the new result for Hawking radiation of RNAdS black hole.
NASA Astrophysics Data System (ADS)
Li, Ran; Zhang, Hongbao; Zhao, Junkun
2016-07-01
Reissner-Nordström Anti-de Sitter (RNAdS) black holes are unstable against the charged scalar field perturbations due to the well-known superradiance phenomenon. We present the time domain analysis of charged scalar field perturbations in the RNAdS black hole background in general dimensions. We show that the instabilities of charged scalar field can be explicitly illustrated from the time profiles of evolving scalar field. By using the Prony method to fit the time evolution data, we confirm the mode that dominates the long time behavior of scalar field is in accordance with the quasinormal mode from the frequency domain analysis. The superradiance origin of the instability can also be demonstrated by comparing the real part of the dominant mode with the superradiant condition of charged scalar field. It is shown that all the unstable modes are superradiant, which is consistent with the analytical result in the frequency domain analysis. Furthermore, we also confirm there exists the rapid exponential growing modes in the RNAdS case, which makes the RNAdS black hole a good test ground to investigate the nonlinear evolution of superradiant instability.
Dias, Goncalo A. S.; Lemos, Jose P. S.
2009-02-15
The Hamiltonian thermodynamics formalism is applied to the general d-dimensional Reissner-Nordstroem-anti-de Sitter black hole with spherical, planar, and hyperbolic horizon topology. After writing its action and performing a Legendre transformation, surface terms are added in order to guarantee a well-defined variational principle with which to obtain sensible equations of motion, and also to allow later on the thermodynamical analysis. Then a Kuchar canonical transformation is done, which changes from the metric canonical coordinates to the physical parameters coordinates. Again, a well-defined variational principle is guaranteed through boundary terms. These terms influence the falloff conditions of the variables and at the same time the form of the new Lagrange multipliers. Reduction to the true degrees of freedom is performed, which are the conserved mass and charge of the black hole. Upon quantization a Lorentzian partition function Z is written for the grand canonical ensemble, where the temperature T and the electric potential {phi} are fixed at infinity. After imposing Euclidean boundary conditions on the partition function, the respective effective action I{sub *}, and thus the thermodynamical partition function, is determined for any dimension d and topology k. This is a quite general action. Several previous results can be then condensed in our single general formula for the effective action I{sub *}. Phase transitions are studied for the spherical case, and it is shown that all the other topologies have no phase transitions. A parallel with the Bose-Einstein condensation can be established. Finally, the expected values of energy, charge, and entropy are determined for the black hole solution.
Scalar particles mass spectrum and localization on FRW branes embedded in a 5D de Sitter bulk
NASA Astrophysics Data System (ADS)
Dariescu, Marina-Aura; Dariescu, Ciprian
2014-07-01
In this paper, we study the scalar fields evolving on a FRW brane embedded in a five-dimensional de Sitter bulk. The scale function and the warp factor, solutions of the Einstein equations, are employed in the five-dimensional Gordon equation describing the massive scalar field, whose wave function depends on the cosmic time and on the extra-dimension. We point out the existence of bounded states and find a minimum value of the effective four-dimensional mass. For the test (scalar) field envelope along the extra-dimension, we derive the corresponding Schrödinger-like equation which is formally that for the Pöschl-Teller potential. Accordingly, we have obtained the quantization law for the mass parameter of the tested scalar field.
Flavor-changing decays of the top quark in 5D warped models
NASA Astrophysics Data System (ADS)
Díaz-Furlong, Alfonso; Frank, Mariana; Pourtolami, Nima; Toharia, Manuel; Xoxocotzi, Reyna
2016-08-01
We study flavor-changing neutral current decays of the top quark in the context of general warped extra dimensions, where the five-dimensional (5D) metric is slightly modified from 5D anti-de Sitter (AdS5 ). These models address the Planck-electroweak hierarchies of the Standard Model and can obey all the low-energy flavor bounds and electroweak precision tests, while allowing the scale of new physics to be at the TeV level, and thus within the reach of the LHC at Run II. We perform the calculation of these exotic top decay rates for the case of a bulk Higgs, and thus include in particular the effect of the additional Kaluza-Klein (KK) Higgs modes running in the loops, along with the usual KK fermions and KK gluons.
De Sitter vacua and N = 2 supergravity
NASA Astrophysics Data System (ADS)
Ogetbil, Orcan Bahri
After reviewing the existing results we give an extensive analysis of the critical points of the potentials of the gauged N = 2 Yang-Mills/Einstein Supergravity theories coupled to tensor- and hyper multiplets in five dimensions. Our analysis includes all the possible gaugings of all N = 2 Maxwell-Einstein supergravity theories whose scalar manifolds are symmetric spaces. In general, the scalar potential gets contributions from R-symmetry gauging, tensor couplings and hyper-couplings. We show that the coupling of a hypermultiplet into a theory whose potential has a non-zero value at its critical point, and gauging a compact subgroup of the hyperscalar isometry group will only rescale the value of the potential at the critical point by a positive factor, and therefore will not change the nature of an existing critical point. However this is not the case for non-compact SO(1, 1) gaugings. An SO(1, 1) gauging of the hyper isometry will generally lead to de Sitter vacua, which is analogous to the ground states found by simultaneously gauging SO(1, 1) symmetry of the real scalar manifold of the five dimensional vector multiplets with U(1)R in earlier literature. SO(m, 1) gaugings with m > 1, which give contributions to the scalar potential only in the Magical Jordan family theories, on the other hand, do not lead to de Sitter vacua. Anti-de Sitter vacua are generically obtained when the U(1)R symmetry is gauged. We also show that it is possible to embed certain generic Jordan family theories into the Magical Jordan family while preserving the nature of the ground states. However the Magical Jordan family theories admit additional vacua which are not found in the generic Jordan family theories. The five dimensional stable de Sitter ground states obtained by gauging SO(1, 1) symmetry of the real symmetric scalar manifold (in particular a generic Jordan family manifold of the vector multiplets) simultaneously with a subgroup Rs of the R-symmetry group descend to four
DeSitter entropy, quantum entanglement and ADS/CFT
NASA Astrophysics Data System (ADS)
Hawking, Stephen; Maldacena, Juan; Strominger, Andrew
2001-05-01
A de Sitter brane-world bounding regions of anti-de Sitter space has a macroscopic entropy given by one-quarter the area of the observer horizon. A proposed variant of the AdS/CFT correspondence gives a dual description of this cosmology as conformal field theory coupled to gravity in de Sitter space. In the case of two-dimensional de Sitter space this provides a microscopic derivation of the entropy, including the one-quarter, as quantum entanglement of the conformal field theory across the horizon.
De Sitter brane-world, localization of gravity, and the cosmological constant
NASA Astrophysics Data System (ADS)
Neupane, Ishwaree P.
2011-04-01
Cosmological models with a de Sitter 3-brane embedded in a 5-dimensional de Sitter spacetime (dS5) give rise to a finite 4D Planck mass similar to that in Randall-Sundrum (RS) brane-world models in anti-de Sitter 5-dimensional spacetime(AdS5). Yet, there arise a few important differences as compared to the results with a flat 3-brane or 4D Minkowski spacetime. For example, the mass reduction formula (MRF) MPl2=M(5)3ℓAdS as well as the relationship MPl2=MPl(4+n)n+2Ln (with L being the average size or the radius of the n extra dimensions) expected in models of product-space (or Kaluza-Klein) compactifications get modified in cosmological backgrounds. In an expanding universe, a physically relevant MRF encodes information upon the 4-dimensional Hubble expansion parameter, in addition to the length and mass parameters L, MPl, and MPl(4+n). If a bulk cosmological constant is present in the solution, then the reduction formula is further modified. With these new insights, we show that the localization of a massless 4D graviton as well as the mass hierarchy between MPl and MPl(4+n) can be explained in cosmological brane-world models. A notable advantage of having a 5D de Sitter bulk is that in this case the zero-mass wave function is normalizable, which is not necessarily the case if the bulk spacetime is anti-de Sitter. In spacetime dimensions D≥7, however, the bulk cosmological constant Λb can take either sign (Λb<0, =0, or >0). The D=6 case is rather inconclusive, in which case Λb may be introduced together with 2-form gauge field (or flux). We obtain some interesting classical gravity solutions that compactify higher-dimensional spacetime to produce a Robertson-Walker universe with de Sitter-type expansion plus one extra noncompact direction. We also show that such models can admit both an effective 4-dimensional Newton constant that remains finite and a normalizable zero-mode graviton wave function.
Conformally covariant quantization of the Maxwell field in de Sitter space
NASA Astrophysics Data System (ADS)
Faci, S.; Huguet, E.; Queva, J.; Renaud, J.
2009-12-01
In this article, we quantize the Maxwell (“massless spin one”) de Sitter field in a conformally invariant gauge. This quantization is invariant under the SO0(2,4) group and consequently under the de Sitter group. We obtain a new de Sitter-invariant two-point function which is very simple. Our method relies on the one hand on a geometrical point of view which uses the realization of Minkowski, de Sitter and anti-de Sitter spaces as intersections of the null cone in R6 and a moving plane, and on the other hand on a canonical quantization scheme of the Gupta-Bleuler type.
Anti-de Sitter universe dynamics in loop quantum cosmology
Bentivegna, Eloisa; Pawlowski, Tomasz
2008-06-15
A model for a flat isotropic universe with a negative cosmological constant {lambda} and a massless scalar field as sole matter content is studied within the framework of loop quantum cosmology. By application of the methods introduced for the model with {lambda}=0, the physical Hilbert space and the set of Dirac observables are constructed. As in that case, the scalar field plays here the role of an emergent time. The properties of the system are found to be similar to those of the k=1 Friedmann-Robertson-Walker (FRW) model: for small energy densities, the quantum dynamics reproduces the classical one, whereas, due to modifications at near-Planckian densities, the big bang and big crunch singularities are replaced by a quantum bounce connecting deterministically the large semiclassical epochs. Thus in loop quantum cosmology the evolution is qualitatively cyclic.
Anti-de Sitter D-branes in curved backgrounds
NASA Astrophysics Data System (ADS)
Huang, Wung-Hong
2005-07-01
We investigate the properties of the AdS D1-branes which are the bound states of a curved D1-brane with n fundamental strings (F1) in the AdS3 spacetime, and the AdS D2-branes which are the axially symmetric bound states of a curved D2-brane with m D0-branes and n fundamental strings in the AdS3 × S3 spacetime. We see that, while the AdS D1-branes asymptotically approach to the event horizon of the AdS3 spacetime the AdS D2-branes will end on it. As the near horizon geometry of the F1/NS5 becomes the spacetime of AdS3 × S3 × T4 with NS-NS three form turned on, we furthermore investigate the corresponding AdS D-branes in the NS5-branes and macroscopic F-strings backgrounds, as an attempt to understand the origin of the AdS D-branes. From the found DBI solutions we see that in the F-strings background, both of the AdS D1-branes and AdS D2-branes will asymptotically approach to the position with a finite distance away from the F-strings. However, the AdS D2-branes therein could also end on the F-strings once it carries sufficient D0-branes charges. We also see that there does not exist any stable AdS D-branes in the NS5-branes backgrounds. We present physical arguments to explain these results, which could help us in understanding the intriguing mechanics of the formation of the AdS D-branes.
Anti-de Sitter universe dynamics in loop quantum cosmology
NASA Astrophysics Data System (ADS)
Bentivegna, Eloisa; Pawlowski, Tomasz
2008-06-01
A model for a flat isotropic universe with a negative cosmological constant Λ and a massless scalar field as sole matter content is studied within the framework of loop quantum cosmology. By application of the methods introduced for the model with Λ=0, the physical Hilbert space and the set of Dirac observables are constructed. As in that case, the scalar field plays here the role of an emergent time. The properties of the system are found to be similar to those of the k=1 Friedmann-Robertson-Walker (FRW) model: for small energy densities, the quantum dynamics reproduces the classical one, whereas, due to modifications at near-Planckian densities, the big bang and big crunch singularities are replaced by a quantum bounce connecting deterministically the large semiclassical epochs. Thus in loop quantum cosmology the evolution is qualitatively cyclic.
Covariant quantization of the Maxwell field in de Sitter space from SO0(2,4)-invariance
NASA Astrophysics Data System (ADS)
Huguet, E.; Faci, S.; Queva, J.; Renaud, J.
2011-03-01
We present a SO0(2,4)-invariant quantization of the free electromagnetic field in de Sitter space. Precisely, we quantize the Maxwell ("massless spin one") de Sitter field in a conformally invariant gauge. This result is obtained thanks to a canonical quantization scheme of the Gupta-Bleuler type and to a geometrical formalism in which the Minkowski, de Sitter and anti-de Sitter spaces are realized as intersections of the five dimensional null cone of ℝ6 and a moving hyperplane. We obtain a new and simple de Sitter invariant two-point function.
Constraints on Meta-stable de Sitter Flux Vacua
Soroush, Masoud
2007-03-05
We consider flux compactification of type IIB string theory as the orientifold limit of an F-theory on a Calabi-Yau fourfold. We show that when supersymmetry is dominantly broken by the axion-dilaton and the contributions of the F-terms associated with complex structure moduli are small, the Hessian of the flux potential always has tachyonic modes for de Sitter vacua. This implies that there exist no meta-stable de Sitter vacua in this limit. Moreover, we find that the stability requirement imposes a relation between the values of cosmological constant and the scale of supersymmetry breaking for non-supersymmetric anti de Sitter vacua in this limit. The proof is general and does rely on the details of the geometry of the compact Calabi-Yau internal space. We finally analyze the consequences of these constraints on the statistics of meta-stable de Sitter vacua and address some other related issues.
Extremal surfaces in de Sitter spacetime
NASA Astrophysics Data System (ADS)
Narayan, K.
2015-06-01
We study extremal surfaces in de Sitter space in the Poincare slicing in the upper patch, anchored on spatial subregions at the future boundary I+, restricted to constant boundary Euclidean time slices (focusing on strip subregions). We find real extremal surfaces of minimal area as the boundaries of past light-cone wedges of the subregions in question: these are null surfaces with vanishing area. We also find complex extremal surfaces as complex extrema of the area functional, and the area is not always real valued. In dS4 the area is real. The area has structural resemblance with entanglement entropy in a dual conformal field theory. There are parallels with analytic continuation from the Ryu-Takayanagi expressions for holographic entanglement entropy in anti-de Sitter. We also discuss extremal surfaces in the de Sitter (dS) black brane and the de Sitter "bluewall" studied previously. The dS4 black brane complex surfaces exhibit a real finite cutoff-independent extensive piece. In the bluewall geometry, there are real surfaces that go from one asymptotic universe to the other through the Cauchy horizons.
Instability of the de Sitter Reissner–Nordstrom black hole in the 1/D expansion
NASA Astrophysics Data System (ADS)
Tanabe, Kentaro
2016-06-01
We study the large D effective theory for D dimensional charged (Anti) de Sitter black holes. Then we show that the de Sitter Reissner–Nordstrom black hole becomes unstable against gravitational perturbations at larger charge than a critical charge in a higher dimension. Furthermore, we find that there is a nontrivial zero-mode static perturbation at the critical charge. The existence of static perturbations suggests the appearance of non-spherical symmetric solution branches of static charged de Sitter black holes. This expectation is confirmed by constructing the non-spherical symmetric static solutions of large D effective equations.
Classical and Quantum Symmetries of de Sitter Space
NASA Astrophysics Data System (ADS)
Anninos, Dionysios Theodoros
2011-10-01
De Sitter space is the maximally symmetric cosmology satisfying Einstein's equations with a positive cosmological constant. It has played a crucial role in the theory of inflationary cosmology. Recent astronomical observations indicate our universe is entering a new asymptotically de Sitter phase, with a mysteriously small value for the cosmological constant. We study several aspects of de Sitter and de Sitter-esque geometries in three and four spacetime dimensions. Particularly, we discuss the asymptotic symmetry group (ASG) of four-dimensional de Sitter space at future infinity, I+ , in Einstein gravity with positive cosmological constant. We find, very much unlike its anti-de Sitter cousin, an infinite dimensional group consisting of the three-dimensional diffeomorphisms acting on I+ . We then move on to rotating black holes in de Sitter space and focus on a limit where the black hole and cosmological horizons coincide. We compute the ASG of the near (cosmological) horizon geometry, the rotating Nariai geometry, which has its own future boundary I+RN and find a Virasoro algebra. This is suggestive of a holographically dual interpretation in terms of a two-dimensional CFT. Scalar waves in the rotating Nariai geometry are studied to provide further evidence for the proposal. Finally, we find toy models of the rotating Nariai geometry in three-dimensional theories of gravity with a gravitational Chern-Simons term and further explore the possibility of a holographic duality. Interestingly, we find a de Sitter like vacuum, warped dS3, whose smooth quotients contain both a cosmological as well as an internal event horizon. In contrast, quotients of Lorentzian dS3 always contain conical singularities.
Decay of magnetic fields in de Sitter and FRW universes
NASA Astrophysics Data System (ADS)
Garcia de Andrade, L. C.; Ferrández, A.
2011-11-01
Magnetic curvature effects, investigated by Barrow and Tsagas (Phys. Rev. D 77, 107302 (2008)), as a mechanism for magnetic field decay in open Friedmann universes ( Λ < 0), are applied to dynamo geometric Ricci flows in 3D curved substrate in laboratory. By simple derivation, a covariant three-dimensional magnetic self-induction equation is obtained. The presence of these curvature effects indicates that de Sitter cosmological constant ( Λ ≥ 0 leads to enhancement in the fast kinematic dynamo action which induces a stretching in plasma flows. From the magnetic growth rate, the strong shear case implies an anti-de Sitter case ( Λ < 0) where BT magnetic decaying fields are possible. For weak shear, fast dynamos are possible. The self-induced equation in Ricci flows is similar to the equation derived by BT in the (3 + 1)-spacetime continuum. Lyapunov-de Sitter metric is obtained from Ricci flow eigenvalue problem. In the de Sitter analogue there is a decay rate of γ ≈ - Λ ≈ -10-35 s-2 from the corresponding cosmological constant Λ. This shows that, even in the dynamo case, the magnetic field growth is slower than de Sitter inflation, which renders strongly support to BT result.
Black hole solutions for scale-dependent couplings: the de Sitter and the Reissner-Nordström case
NASA Astrophysics Data System (ADS)
Koch, Benjamin; Rioseco, Paola
2016-02-01
Allowing for scale dependence of the gravitational couplings leads to a generalization of the corresponding field equations. In this work, these equations are solved for the Einstein-Hilbert and the Einstein-Maxwell case, leading to generalizations of the (Anti)-de Sitter and the Reissner-Nordström black holes. These solutions are discussed and compared to their classical counterparts.
Constraints on a spherically symmetric 5-d braneworld
NASA Astrophysics Data System (ADS)
Capistrano, A. J. S.
2013-12-01
We study the effect of the extrinsic curvature within the context of braneworld with constant curvature and the restrictions on a spherically symmetric geometry embedded in a 5-d bulk. As a counterexample, we recover the Schwarzschild-de Sitter black hole but with umbilical points. In a second case we find the correct geometrical structure of a black hole but the Newtonian gravity cannot be restored implying that a higher dynamical embedding must be considered.
A note on Schwarzschild-de Sitter black holes in mimetic F(R) gravity
NASA Astrophysics Data System (ADS)
Oikonomou, V. K.
2016-05-01
In this paper, we investigate the conditions under which a Schwarzschild-de Sitter black hole spacetime is a solution of the mimetic F(R) gravity with Lagrange multiplier and potential. As we demonstrate, the resulting mimetic F(R) gravity is a slight modification of the ordinary F(R) gravity case, however the resulting perturbation equations are not in all cases identical to the ordinary F(R) gravity case. In the latter case, the perturbation equations are identical to the ones corresponding to the Reissner-Nordström anti-de Sitter black hole.
'Micromanaging de Sitter holography'
Dong, Xi; Horn, Bart; Silverstein, Eva; Torroba, Gonzalo; /SLAC /Stanford U., Phys. Dept. /Santa Barbara, KITP
2010-08-26
We develop tools to engineer de Sitter vacua with semi-holographic duals, using elliptic fibrations and orientifolds to uplift Freund-Rubin compactifications with CFT duals. The dual brane construction is compact and constitutes a microscopic realization of the dS/dS correspondence, realizing d-dimensional de Sitter space as a warped compactification down to (d-1)-dimensional de Sitter gravity coupled to a pair of large-N matter sectors. This provides a parametric microscopic interpretation of the Gibbons-Hawking entropy. We illustrate these ideas with an explicit class of examples in three dimensions, and describe ongoing work on four-dimensional constructions. The Gibbons-Hawking entropy of the de Sitter horizon [1] invites a microscopic interpretation and a holographic formulation of inflating spacetimes. Much progress was made in the analogous problem in black hole physics using special black holes in string theory whose microstates could be reliably counted, such as those analyzed in [2,3]; this led to the AdS/CFT correspondence [4]. In contrast, a microscopic understanding of the entropy of de Sitter space is more difficult for several reasons including its potential dynamical connections to other backgrounds (metastability), the absence of a non-fluctuating timelike boundary, and the absence of supersymmetry. In this paper, we develop a class of de Sitter constructions in string theory, built up from AdS/CFT dual pairs along the lines of [5], which are simple enough to provide a microscopic accounting of the parametric scaling of the Gibbons-Hawking entropy. These models realize microscopically a semi-holographic description of metastable de Sitter space which had been derived macroscopically in [6]. It would also be interesting to connect this to other approaches to de Sitter holography such as [7, 8] and to other manifestations of the de Sitter entropy such as [9]. The construction is somewhat analogous to neutral black branes analyzed in [11]. We will
NASA Astrophysics Data System (ADS)
Anabitarte, M.; Bellini, M.; Aguilar, José Edgar Madriz
2010-01-01
We extend to 5D an approach of a 4D non-perturbative formalism to study scalar metric fluctuations of a 5D Riemann-flat de Sitter background metric. In contrast with the results obtained in 4D, the spectrum of cosmological scalar metric fluctuations during inflation can be scale invariant and the background inflaton field can take sub-Planckian values.
Silverstein, Eva; /Stanford U., Phys. Dept. /SLAC
2008-01-07
We present a framework for de Sitter model building in type IIA string theory, illustrated with specific examples. We find metastable dS minima of the potential for moduli obtained from a compactification on a product of two Nil three-manifolds (which have negative scalar curvature) combined with orientifolds, branes, fractional Chern-Simons forms, and fluxes. As a discrete quantum number is taken large, the curvature, field strengths, inverse volume, and four dimensional string coupling become parametrically small, and the de Sitter Hubble scale can be tuned parametrically smaller than the scales of the moduli, KK, and winding mode masses. A subtle point in the construction is that although the curvature remains consistently weak, the circle fibers of the nilmanifolds become very small in this limit (though this is avoided in illustrative solutions at modest values of the parameters). In the simplest version of the construction, the heaviest moduli masses are parametrically of the same order as the lightest KK and winding masses. However, we provide a method for separating these marginally overlapping scales, and more generally the underlying supersymmetry of the model protects against large corrections to the low-energy moduli potential.
Asymptotically warped anti-de Sitter spacetimes in topologically massive gravity
NASA Astrophysics Data System (ADS)
Henneaux, Marc; Martínez, Cristián; Troncoso, Ricardo
2011-12-01
Asymptotically warped AdS spacetimes in topologically massive gravity with negative cosmological constant are considered in the case of spacelike stretched warping, where black holes have been shown to exist. We provide a set of asymptotic conditions that accommodate solutions in which the local degree of freedom (the “massive graviton”) is switched on. An exact solution with this property is explicitly exhibited and possesses a slower falloff than the warped AdS black hole. The boundary conditions are invariant under the semidirect product of the Virasoro algebra with a u(1) current algebra. We show that the canonical generators are integrable and finite. When the graviton is not excited, our analysis is compared and contrasted with earlier results obtained through the covariant approach to conserved charges. In particular, we find agreement with the conserved charges of the warped AdS black holes as well as with the central charges in the algebra.
One-loop effective action and Schwinger effect in (anti-) de Sitter space
NASA Astrophysics Data System (ADS)
Cai, Rong-Gen; Kim, Sang Pyo
2014-09-01
We study the Schwinger mechanism by a uniform electric field in dS2 and AdS2 and the curvature effect on the Schwinger effect, and further propose a thermal interpretation of the Schwinger formula in terms of the Gibbons-Hawking temperature and the Unruh temperature for an accelerating charge in dS2 and an analogous expression in AdS2. The exact one-loop effective action is found in the proper-time integral in each space, which is determined by the effective mass, the Maxwell scalar, and the scalar curvature, and whose pole structure gives the imaginary part of the effective action and the exact pair-production rate. The exact pair-production rate is also given the thermal interpretation.
Conformally Coupled Scalars, Instantons, and Vacuum Instability in 4D Anti-de Sitter Space
Haro, Sebastian de; Papadimitriou, Ioannis; Petkou, Anastasios C.
2007-06-08
We show that a scalar field conformally coupled to AdS gravity in four dimensions with a quartic self-interaction can be embedded into M theory. The holographic effective potential is exactly calculated, allowing us to study nonperturbatively the stability of AdS{sub 4} in the presence of the conformally coupled scalar. It is shown that there exists a one-parameter family of conformal scalar boundary conditions for which the boundary theory has an unstable vacuum. In this case, the bulk theory has instanton solutions that mediate the decay of the AdS{sub 4} space. These results match nicely with the vacuum structure and the existence of instantons in an effective three-dimensional boundary model.
Quasinormal frequencies of asymptotically anti-de Sitter black holes in two dimensions
NASA Astrophysics Data System (ADS)
Cordero, R.; López-Ortega, A.; Vega-Acevedo, I.
2012-04-01
We calculate exactly the quasinormal frequencies of Klein-Gordon and Dirac test fields propagating in 2D uncharged Achucarro-Ortiz black hole. For both test fields we study whether the quasinormal frequencies are well defined in the massless limit. We use their values to discuss the classical stability of the quasinormal modes in uncharged Achucarro-Ortiz black hole and to check the recently proposed Time Times Temperature bound. Furthermore we extend some of these results to the charged Achucarro-Ortiz black hole.
Anti-de Sitter-space/conformal-field-theory correspondence and large-N volume independence
Poppitz, Erich; Uensal, Mithat
2010-09-15
We study the Eguchi-Kawai reduction in the strong-coupling domain of gauge theories via the gravity dual of N=4 super-Yang-Mills on R{sup 3}xS{sup 1}. We show that D-branes geometrize volume independence in the center-symmetric vacuum and give supergravity predictions for the range of validity of reduced large-N models at strong coupling.
On a canonical quantization of 3D Anti de Sitter pure gravity
NASA Astrophysics Data System (ADS)
Kim, Jihun; Porrati, Massimo
2015-10-01
We perform a canonical quantization of pure gravity on AdS 3 using as a technical tool its equivalence at the classical level with a Chern-Simons theory with gauge group SL(2,{R})× SL(2,{R}) . We first quantize the theory canonically on an asymptotically AdS space -which is topologically the real line times a Riemann surface with one connected boundary. Using the "constrain first" approach we reduce canonical quantization to quantization of orbits of the Virasoro group and Kähler quantization of Teichmüller space. After explicitly computing the Kähler form for the torus with one boundary component and after extending that result to higher genus, we recover known results, such as that wave functions of SL(2,{R}) Chern-Simons theory are conformal blocks. We find new restrictions on the Hilbert space of pure gravity by imposing invariance under large diffeomorphisms and normalizability of the wave function. The Hilbert space of pure gravity is shown to be the target space of Conformal Field Theories with continuous spectrum and a lower bound on operator dimensions. A projection defined by topology changing amplitudes in Euclidean gravity is proposed. It defines an invariant subspace that allows for a dual interpretation in terms of a Liouville CFT. Problems and features of the CFT dual are assessed and a new definition of the Hilbert space, exempt from those problems, is proposed in the case of highly-curved AdS 3.
A de Sitter tachyon thick braneworld
Germán, Gabriel; Herrera-Aguilar, Alfredo; Malagón-Morejón, Dagoberto; Mora-Luna, Refugio Rigel; Rocha, Roldão da E-mail: aha@fis.unam.mx E-mail: rigel@ifm.umich.mx
2013-02-01
Among the multiple 5D thick braneworld models that have been proposed in the last years, in order to address several open problems in modern physics, there is a specific one involving a tachyonic bulk scalar field. Delving into this framework, a thick braneworld with a cosmological background induced on the brane is here investigated. The respective field equations — derived from the model with a warped 5D geometry — are highly non-linear equations, admitting a non-trivial solution for the warp factor and the tachyon scalar field as well, in a de Sitter 4D cosmological background. Moreover, the non-linear tachyonic scalar field, that generates the brane in complicity with warped gravity, has the form of a kink-like configuration. Notwithstanding, the non-linear field equations restricting character does not allow one to easily find thick brane solutions with a decaying warp factor which leads to the localization of 4D gravity and other matter fields. We derive such a thick brane configuration altogether in this tachyon-gravity setup. When analyzing the spectrum of gravity fluctuations in the transverse traceless sector, the 4D gravity is shown to be localized due to the presence of a single zero mode bound state, separated by a continuum of massive Kaluza-Klein (KK) modes by a mass gap. It contrasts with previous results, where there is a KK massive bound excitation providing no clear physical interpretation. The mass gap is determined by the scale of the metric parameter H. Finally, the corrections to Newton's law in this model are computed and shown to decay exponentially. It is in full compliance to corrections reported in previous results (up to a constant factor) within similar braneworlds with induced 4D de Sitter metric, despite the fact that the warp factor and the massive modes have a different form.
The seed of magnetic monopoles in the early inflationary universe from a 5D vacuum state
NASA Astrophysics Data System (ADS)
Romero, Jesús Martín; Bellini, Mauricio
2009-04-01
Starting from a 5D Riemann flat metric, we have induced an effective 4D Hermitian metric which has an antisymmetric part which is purely imaginary. We have worked an example in which both, non-metricity and cotorsion are zero. We obtained that the production of monopoles should be insignificant at the end of inflation and the tensor metric should come asymptotically diagonal and describing a nearly 4D de Sitter expansion.
NASA Astrophysics Data System (ADS)
Rubin, Vera C.
2010-07-01
Charlotte Moore Sitterly was a scientist in an era when it was rare for a woman to have the opportunity to devote her life to forefront science. Following her graduation from Swarthmore College in 1920, she accepted a position at Princeton University as an assistant to Henry Norris Russell. In 1925 she started a study of the solar spectrum. She could then not know that she would devote much of her scientific career to gathering basic atomic data that are invaluable to the scientific community, even today. In 1931 she obtained a Ph.D. degree at the University of California, Berkeley, and returned to Princeton as a staff member of the Princeton University Observatory. In 1945 Moore moved to the National Bureau of Standards (NBS), to supervise preparation of the widely-used tables of atomic energy levels. Following the successful launching (1946) of a V2 rocket to obtain the ultraviolet spectrum of the Sun, she started working also with Richard Tousey and his group at the Naval Research Laboratory (NRL). Ultimately, they extended the solar spectrum down to 2200 angstroms. She continued her affiliations with both the NBS and the NRL until her death in 1990. Charlotte Moore was a rare scientist who devoted her career to obtaining accurate numbers, thus enabling the scientific community to open her tables and know that the data are reliable.
Infrared surprises in the de Sitter universe
NASA Astrophysics Data System (ADS)
Moschella, Ugo
2016-06-01
We describe a few unexpected features of de Sitter quantum field theory (QFT) that have no Minkowskian counterparts. These phenomena show that even when the cosmological constant is tiny a Minkowskian way of fast thinking about de Sitter can lead to mistakes and that de Sitter QFT is essentially different from standard relativistic (Minkowskian) QFT.
Aguilar, José Edgar Madriz; Bellini, Mauricio E-mail: mbellini@mdp.edu.ar
2010-11-01
We study scalar field fluctuations of the inflaton field in an early inflationary universe on an effective 4D Schwarzschild-de Sitter (SdS) metric, which is obtained after make a planar coordinate transformation on a 5D Ricci-flat Schwarzschild-de Sitter (SdS) static metric. We obtain the important result that the spectrum of fluctuations at zeroth order is independent of the scalar field mass M on Schwarzschild scales, while on cosmological scales it exhibits a mass dependence. However, in the first-order expansion, the spectrum depends of the inflaton mass and the amplitude is linear with the Black-Hole (BH) mass m.
An evaluation of a sitter reduction program intervention.
Spiva, LeeAnna; Feiner, Therese; Jones, Darcia; Hunter, Donna; Petefish, Jayne; VanBrackle, Lewis
2012-01-01
Hospitals use sitters as an alternative to reduce patient falls. The purpose of the study was to evaluate the effectiveness of a sitter reduction program by examining the differences between sitter use and falls in an acute care hospital. Findings indicate that a significant decrease in sitter use and falls remained constant. Reducing sitter use is possible without significantly increasing fall rates. PMID:22692004
5d relativistic hydrodynamics and cosmology
NASA Astrophysics Data System (ADS)
Gemelli, Gianluca
2008-05-01
We consider the evolution of a perfect fluid in 5d relativity. This picture reveals a 4d particle production effect, the source of particle production originating from 5d geometry, and vanishing if the flow is isentropic. The result holds in 5d special relativity as well as in 5d general relativity, no matter if the cosmological fluid is a test-fluid or a self-gravitating fluid.
Inflationary Dark Energy from a Condensate of Spinors in a 5d Vacuum
NASA Astrophysics Data System (ADS)
Sánchez, Pablo Alejandro; Bellini, Mauricio
2013-11-01
What is the physical origin of dark energy? Could this energy be originated by other fields than the inflaton? In this paper, we explore the possibility that the expansion of the universe can be driven by a condensate of spinors. These spinors are free of interactions on five-dimensional (5D) relativistic vacuum in an extended de Sitter spacetime. The extra coordinate is considered as noncompact. After making a static foliation on the extra coordinate, we obtain an effective four-dimensional (4D) (inflationary) de Sitter expansion which describes an inflationary universe. In view of our results, we conclude that the condensate of spinors here studied could be an interesting candidate to explain the presence of dark energy in the early universe.
Thick brane isotropization in a generalized 5D anisotropic standing wave braneworld model
NASA Astrophysics Data System (ADS)
Gogberashvili, Merab; Herrera–Aguilar, Alfredo; Malagón–Morejón, Dagoberto; Mora–Luna, Refugio Rigel; Nucamendi, Ulises
2013-04-01
We study a smooth cosmological solution within a generalized 5D standing wave braneworld modeled by gravity and a phantom scalar field. In this model the 3-brane is anisotropically warped along its spatial dimensions and contains a novel time-dependent scale factor that multiplies the anisotropic spatial interval of the 5D metric, a fact that allows us to study cosmological effects. By explicitly solving the bulk field equations we found a natural mechanism which isotropizes the braneworld for a wide class of natural initial conditions. We are able to give a physical interpretation of the anisotropic dissipation: as the anisotropic energy of the 3-brane rapidly leaks into the bulk through the nontrivial components of the nonlocal Weyl tensor projected to the brane, the bulk becomes less isotropic. At the same time, under the action of the 4D cosmological constant, the anisotropic braneworld super-exponentially isotropizes by itself, rendering a 3-brane with de Sitter symmetry embedded in a 5D de Sitter space-time, while the phantom scalar field exponentially vanishes.
Super-exponential inflation from a dynamical foliation of a 5D vacuum state
NASA Astrophysics Data System (ADS)
Bellini, Mauricio
2011-09-01
We introduce super-exponential inflation ( ω < - 1 ) from a 5D Riemann-flat canonical metric on which we make a dynamical foliation. The resulting metric describes a super accelerated expansion for the early universe well known as super-exponential inflation that, for very large times, tends to an asymptotic de Sitter (vacuum dominated) expansion. The scalar field fluctuations are analyzed. The important result here obtained is that the spectral index for energy density fluctuations is not scale invariant, and for cosmological scales becomes n ( k < k ) ≃ 1 . However, for astrophysical scales this spectrum changes to negative values n ( k > k ) < 0 .
Passing to an effective 4D phantom cosmology from 5D vacuum theory of gravity
NASA Astrophysics Data System (ADS)
Aguilar, José Edgar Madriz; Bellini, Mauricio
2008-02-01
Starting from a five-dimensional (5D) vacuum theory of gravity where the extra coordinate is considered as non-compact, we investigate the possibility of inducing four-dimensional (4D) phantom scenarios by applying form-invariance symmetry transformations. In particular we obtain phantom scenarios for two cosmological frameworks. In the first framework we deal with an induced 4D de Sitter expansion and in the second one a 4D induced model where the expansion of the universe is dominated by a decreasing cosmological parameter Λ(t) is discussed.
Noncommutative de Sitter and FRW spaces
NASA Astrophysics Data System (ADS)
Burić, Maja; Madore, John
2015-10-01
Several versions of fuzzy four-dimensional de Sitter space are constructed using the noncommutative frame formalism. Although all noncommutative spacetimes which are found have commutative de Sitter metric as a classical limit, the algebras and the differential calculi which define them have many differences, which we derive and discuss.
De Sitter space in gauge/gravity duality
NASA Astrophysics Data System (ADS)
Anguelova, Lilia; Suranyi, Peter; Wijewardhana, L. C. R.
2015-10-01
We investigate gauge/gravity duality for gauge theories in de Sitter space. More precisely, we study a five-dimensional consistent truncation of type IIB supergravity, which encompasses a wide variety of gravity duals of strongly coupled gauge theories, including the Maldacena-Nunez solution and its walking deformations. We find several solutions of the 5d theory with dS4 spacetime and nontrivial profiles for (some of) the scalars along the fifth (radial) direction. In the process, we prove that one of the equations of motion becomes dependent on the others, for nontrivial warp factor. This dependence reduces the number of field equations and, thus, turns out to be crucial for the existence of solutions with (A) dS 4 spacetime. Finally, we comment on the implications of our dS4 solutions for building gravity duals of Glueball Inflation.
Infrared divergences in de Sitter space
Polarski, D. Service d'Astrophysique, CEN Saclay, 91191 Gif-sur-Yvette CEDEX, France)
1991-03-15
Infrared divergences in de Sitter space are considered. It is shown that symmetry breaking is unavoidable only when the infrared divergence is strong enough. The static vacuum has no symmetry breaking despite the presence of an infrared divergence.
NASA Astrophysics Data System (ADS)
Dadras, Pouria; Firouzjaee, J. T.; Mansouri, Reza
2012-11-01
We propose a special solution of Einstein equations in the general Vaidya form representing a dynamical black hole having horizon cross-sections with toroidal topology. The concrete model enables us to study for the first time dynamical horizons with toroidal topology, its area law, and the question of matter flux inside the horizon, without using a cut-and-paste technology to construct the solution.
Negative mass bubbles in de Sitter spacetime
NASA Astrophysics Data System (ADS)
Mbarek, Saoussen; Paranjape, M. B.
2014-11-01
We study the possibility of the existence of negative mass bubbles within a de Sitter spacetime background with matter content corresponding to a perfect fluid. It is shown that there exist configurations of the perfect fluid that satisfy everywhere the dominant energy condition, the Einstein equations and the equations of hydrostatic equilibrium which asymptotically approach the exact solution of Schwarzschild—de Sitter spacetime with a negative mass.
General instanton counting and 5d SCFT
NASA Astrophysics Data System (ADS)
Hwang, Chiung; Kim, Joonho; Kim, Seok; Park, Jaemo
2015-07-01
Instanton partition functions of 5d gauge theories are Witten indices for the ADHM gauged quantum mechanics with (0, 4) SUSY. We derive the integral contour prescriptions for these indices using the Jeffrey-Kirwan method, for gauge theories with hypermultiplets in various representations. The results can be used to study various 4d/5d/6d QFTs. In this paper, we study 5d SCFTs which are at the UV fixed points of 5d SYM theories. In particular, we focus on the Sp( N ) theories with N f ≤ 7 fundamental and 1 antisymmetric hypermultiplets, living on the D4-D8-O8 systems. Their superconformal indices calculated from instantons all show symmetry enhancements. We also discuss some aspects of the 6d SCFTs living on the M5-M9 system. It is crucial to understand the UV incompleteness of the 5d SYM, coming from small instantons in our problem. We explain in our examples how to fix them. As an aside, we derive the index for general gauged quantum mechanics with (0 , 2) SUSY.
Faizal, Mir; Higuchi, Atsushi
2008-09-15
The propagators of the Faddeev-Popov (FP) ghosts for Yang-Mills theories and perturbative quantum gravity in the covariant gauge are infrared (IR) divergent in de Sitter spacetime. We point out, however, that the modes responsible for these divergences will not contribute to loop diagrams in computations of time-ordered products in either Yang-Mills theories or perturbative quantum gravity. Therefore, we propose that the IR-divergent FP-ghost propagator should be regularized by a small mass term that is sent to zero in the end of any perturbative calculations. This proposal is equivalent to using the effective FP-ghost propagators, which we present in an explicit form, obtained by removing the modes responsible for the IR divergences. We also make some comments on the corresponding propagators in anti-de Sitter spacetime.
5-D Choptuik critical exponent and holography
Bland, J.; Kunstatter, G.
2007-05-15
Recently, a holographic argument was used to relate the saturation exponent, {gamma}{sub BFKL}, of 4-dimensional Yang-Mills theory in the Regge limit to the Choptuik critical scaling exponent, {gamma}{sub 5d}, in 5-dimensional black hole formation via scalar field collapse [L. Alvarez-Gaume, C. Gomez, and M. A. Vazquez-Mozo, arXiv:hep-th/0611312.]. Remarkably, the numerical value of the former agreed quite well with previous calculations of the latter. We present new results of an improved calculation of {gamma}{sub 5d} with substantially decreased numerical error. Our current result is {gamma}{sub 5d}=0.4131{+-}0.0001, which is close to, but not in strict agreement with, the value of {gamma}{sub BFKL}=0.409 552 quoted in [L. Alvarez-Gaume, C. Gomez, and M. A. Vazquez-Mozo, arXiv:hep-th/0611312.].
NASA Astrophysics Data System (ADS)
Nishi, Masato
2016-07-01
We discuss the large mass hierarchy problem in a braneworld model which represents our acceleratively expanding universe. The Randall-Sundrum (RS) model with one extra warped dimension added to a flat four-dimensional space-time cannot describe our expanding universe. Here, we study instead the de Sitter thin brane model. This is described by the same action as that for the RS model, but the four-dimensional space-time on the branes is dS_4. We study the model for both the cases of positive five-dimensional cosmological constant Λ_5 and a negative one. In the positive Λ_5 case, the four-dimensional large hierarchy necessitates a five-dimensional large hierarchy, and we cannot get a natural explanation. On the other hand, in the negative Λ_5 case, the large hierarchy is naturally realized in the five-dimensional theory in the same manner as in the RS model. Moreover, another large hierarchy between the Hubble parameter and the Planck scale is realized by the O(10^2) hierarchy of the five-dimensional quantities. Finally, we find that the lightest mass of the massive Kaluza-Klein modes and the intervals of the mass spectrum are of order 10^2 GeV, which are the same as in the RS case and do not depend on the value of the Hubble parameter.
Cosmological perturbations in inflation and in de Sitter space
NASA Astrophysics Data System (ADS)
Pimentel, Guilherme Leite
holography and entanglement entropy to study superhorizon correlations in quantum field theories in de Sitter space. The entropy has interesting terms that have no equivalent in flat space field theories. These new terms are due to particle creation in an expanding universe. The entropy is calculated directly for free massive scalar theories. For theories with holographic duals, it is determined by the area of some extremal surface in the bulk geometry. We calculate the entropy for different classes of holographic duals. For one of these classes, the holographic dual geometry is an asymptotically Anti-de Sitter space that decays into a crunching cosmology, an open Friedmann-Robertson-Walker universe. The extremal surface used in the calculation of the entropy lies almost entirely on the slice of maximal scale factor of the crunching cosmology.
Supersymmetry and Lorentz Violation in 5D
Garcia-Aguilar, J. D.; Perez-Lorenzana, A.; Pedraza-Ortega, O.
2011-10-14
We present a study for a Supersymmetric field theory with Lorentz-Violation terms in 5D. We perform the analysis in the context of the Berger-Kostelecky model (BK), adding one compactified dimension that explicitly breaks the Lorentz invariance. We introduce terms that encode this breaking, and find non trivial restrictions over boundary conditions of fields that one needs to close the supersymmetric algebra.
Supersymmetry and Lorentz Violation in 5D
NASA Astrophysics Data System (ADS)
García-Aguilar, J. D.; Pérez-Lorenzana, A.; Pedraza-Ortega, O.
2011-10-01
We present a study for a Supersymmetric field theory with Lorentz-Violation terms in 5D. We perform the analysis in the context of the Berger-Kostelecky model (BK), adding one compactified dimension that explicitly breaks the Lorentz invariance. We introduce terms that encode this breaking, and find non trivial restrictions over boundary conditions of fields that one needs to close the supersymmetric algebra.
A natural fuzzyness of de Sitter spacetime
NASA Astrophysics Data System (ADS)
Gazeau, Jean-Pierre; Toppan, Francesco
2010-01-01
A non-commutative structure for de Sitter spacetime is naturally introduced by replacing ('fuzzyfication') the classical variables of the bulk in terms of the dS analogs of the Pauli-Lubanski operators. The dimensionality of the fuzzy variables is determined by a Compton length and the commutative limit is recovered for distances much larger than the Compton distance. The choice of the Compton length determines different scenarios. In scenario I the Compton length is determined by the limiting Minkowski spacetime. A fuzzy dS in scenario I implies a lower bound (of the order of the Hubble mass) for the observed masses of all massive particles (including massive neutrinos) of spin s > 0. In scenario II the Compton length is fixed in the de Sitter spacetime itself and grossly determines the number of finite elements ('pixels' or 'granularity') of a de Sitter spacetime of a given curvature.
Observation assistants: sitter effectiveness and industry measures.
Harding, Andrew D
2010-01-01
Patient safety remains a strategic goal and of societal importance for better health care. Direct observation remains an ineffective and expensive means of providing for patient safety. The nursing quality team found that using assessment tools helped to objectively categorize which patients are at risk. Defining patient volume, actual productive sitter usage, and assessing demand for patients in psychiatric crisis and patients at high risk to fall in the form of average daily census provided an easy-to-translate, familiar unit of measure to compare patient volume to demand and utilization. The sitter utilization case was unable to provide correlation of sitter use to decreased fall rates, elopement, or assault behaviors. Currently, there is no research to suggest the use of constant observation reduces the risk of patient harm related to their risk for falling or harming themselves. PMID:21158254
Remark on massive particle's de Sitter tunneling
Jiang, Qing-Quan; Chen, De-You; Wen, Dan E-mail: deyouchen@126.com
2013-11-01
In the work [J. Y. Zhang and Z. Zhao, Massive particles's black hole tunneling and de Sitter tunneling, Nucl. Phys. B 725 (2005) 173.], the Hawking radiation of the massive particle via tunneling from the de Sitter cosmological horizon has been first described in the tunneling framework. However, the geodesic equation of the massive particle was unnaturally and awkwardly defined there by investigating the relation between the group and phase velocity. In this paper, we start from the Lagrangian analysis on the action to naturally produce the geodesic equation of the tunneling massive particle. Then, based on the new definition for the geodesic equation, we revisit the Hawking radiation of the massive particle via tunneling from the de Sitter cosmological horizon. It is noteworthy that, the highlight of our work is a new and important development of the Parikh-Wilczek's tunneling method, which can make it more physical.
Entropic uncertainty relation in de Sitter space
NASA Astrophysics Data System (ADS)
Jia, Lijuan; Tian, Zehua; Jing, Jiliang
2015-02-01
The uncertainty principle restricts our ability to simultaneously predict the measurement outcomes of two incompatible observables of a quantum particle. However, this uncertainty could be reduced and quantified by a new Entropic Uncertainty Relation (EUR). By the open quantum system approach, we explore how the nature of de Sitter space affects the EUR. When the quantum memory A freely falls in the de Sitter space, we demonstrate that the entropic uncertainty acquires an increase resulting from a thermal bath with the Gibbons-Hawking temperature. And for the static case, we find that the temperature coming from both the intrinsic thermal nature of the de Sitter space and the Unruh effect associated with the proper acceleration of A also brings effect on entropic uncertainty, and the higher the temperature, the greater the uncertainty and the quicker the uncertainty reaches the maximal value. And finally the possible mechanism behind this phenomenon is also explored.
NASA Astrophysics Data System (ADS)
Akcay, Sarp; Matzner, Richard A.
2011-04-01
It is now widely accepted that the universe as we understand it is accelerating in expansion and fits the de Sitter model rather well. As such, a realistic assumption of black holes must place them on a de Sitter background and not Minkowski as is typically done in general relativity. The most astrophysically relevant black hole is the uncharged, rotating Kerr solution, a member of the more general Kerr-Newman metrics. A generalization of the rotating Kerr black hole to a solution of the Einstein's equation with a cosmological constant Λ was discovered by Carter (1973 Les Astres Occlus ed B DeWitt and C M DeWitt (New York: Gordon and Breach)). It is typically referred to as the Kerr-de Sitter spacetime. Here, we discuss the horizon structure of this spacetime and its dependence on Λ. We recall that in a Λ > 0 universe, the term 'extremal black hole' refers to a black hole with angular momentum J > M2. We obtain explicit numerical results for the black hole's maximal spin value and get a distribution of admissible Kerr holes in the (Λ, spin) parameter space. We look at the conformal structure of the extended spacetime and the embedding of the 3-geometry of the spatial hypersurfaces. In analogy with Reissner-Nordström-de Sitter spacetime, in particular by considering the Kerr-de Sitter causal structure as a distortion of the Reissner-Nordström-de Sitter one, we show that spatial sections of the extended spacetime are 3-spheres containing two-dimensional topologically spherical sections of the horizons of Kerr holes at the poles. Depending on how a t = constant 3-space is defined, these holes may be seen as black or white holes (four possible combinations).
New instabilities of de Sitter spacetimes
Copsey, Keith; Mann, Robert
2010-04-15
We construct an instanton describing the pair production of non-Kaluza-Klein bubbles of nothing in higher odd-dimensional de Sitter spaces. In addition to showing that higher-dimensional de Sitter spaces have a nonzero probability to become topologically nontrivial, this process provides direct evidence for the association of entropy with cosmological horizons as well as evidence that non-Kaluza-Klein bubbles of nothing are a necessary ingredient in string theory or any other consistent quantum theory of gravity in higher dimensions.
NASA Astrophysics Data System (ADS)
Membiela, Federico Agustín; Bellini, Mauricio
2010-02-01
Using a semiclassical approach to Gravitoelectromagnetic Inflation (GEMI), we study the origin and evolution of seminal inflaton and electromagnetic fields in the early inflationary universe from a 5D vacuum state. The difference with other previous works is that in this one we use a Lorentz gauge. Our formalism is naturally not conformal invariant on the effective 4D de Sitter metric, which make possible the super adiabatic amplification of magnetic field modes during the early inflationary epoch of the universe on cosmological scales.
The fifth spectrum of platinum (Pt V): Analysis of the (5d6 + 5d5 6 s) - 5d5 6 p transition array
NASA Astrophysics Data System (ADS)
Azarov, Vladimir I.; Gayasov, Robert R.
2016-03-01
The spectrum of platinum was observed in the 300-2100 Å wavelength region. The (5d6 + 5d5 6 s) - 5d5 6 p transition array of four times ionized platinum, Pt V, has been investigated and 1659 spectral lines have been classified in the region of 460-1730 Å. The analysis has led to the determination of the 5d6, 5d5 6 s and 5d5 6 p configurations. Thirty two of 34 theoretically possible 5d6 levels, 45 of 74 possible 5d5 6 s levels and 181 of 214 possible 5d5 6 p levels have been established. The orthogonal operators technique was used to calculate the level structure and transition probabilities. The energy parameters have been determined by the least squares fit to the observed levels. Calculated transition probability and energy values, as well as LS-compositions obtained from the fitted parameters are presented.
Initial development of 5D COGENT
NASA Astrophysics Data System (ADS)
Cohen, R. H.; Lee, W.; Dorf, M.; Dorr, M.
2015-11-01
COGENT is a continuum gyrokinetic edge code being developed by the by the Edge Simulation Laboratory (ESL) collaboration. Work to date has been primarily focussed on a 4D (axisymmetric) version that models transport properties of edge plasmas. We have begun development of an initial 5D version to study edge turbulence, with initial focus on kinetic effects on blob dynamics and drift-wave instability in a shearless magnetic field. We are employing compiler directives and preprocessor macros to create a single source code that can be compiled in 4D or 5D, which helps to ensure consistency of physics representation between the two versions. A key aspect of COGENT is the employment of mapped multi-block grid capability to handle the complexity of diverter geometry. It is planned to eventually exploit this capability to handle magnetic shear, through a series of successively skewed unsheared grid blocks. The initial version has an unsheared grid and will be used to explore the degree to which a radial domain must be block decomposed. We report on the status of code development and initial tests. Work performed for USDOE, at LLNL under contract DE-AC52-07NA27344.
Schwinger effect in de Sitter space
NASA Astrophysics Data System (ADS)
Fröb, Markus B.; Garriga, Jaume; Kanno, Sugumi; Sasaki, Misao; Soda, Jiro; Tanaka, Takahiro; Vilenkin, Alexander
2014-04-01
We consider Schwinger pair production in 1+1 dimensional de Sitter space, filled with a constant electric field E. This can be thought of as a model for describing false vacuum decay beyond the semiclassical approximation, where pairs of a quantum field phi of mass m and charge e play the role of vacuum bubbles. We find that the adiabatic ``in" vacuum associated with the flat chart develops a space-like expectation value for the current J, which manifestly breaks the de Sitter invariance of the background fields. We derive a simple expression for J(E), showing that both ``upward" and ``downward" tunneling contribute to the build-up of the current. For heavy fields, with m2 gg eE,H2, the current is exponentially suppressed, in agreement with the results of semiclassical instanton methods. Here, H is the inverse de Sitter radius. On the other hand, light fields with m ll H lead to a phenomenon of infrared hyperconductivity, where a very small electric field mHlesssimeE ll H2 leads to a very large current J ~ H3/E. We also show that all Hadamard states for phi necessarily break de Sitter invariance. Finally, we comment on the role of initial conditions, and ``persistence of memory" effects.
Schwinger effect in de Sitter space
Fröb, Markus B.; Garriga, Jaume; Kanno, Sugumi; Sasaki, Misao; Tanaka, Takahiro; Soda, Jiro; Vilenkin, Alexander E-mail: jaume.garriga@ub.edu E-mail: misao@yukawa.kyoto-u.ac.jp E-mail: tanaka@yukawa.kyoto-u.ac.jp
2014-04-01
We consider Schwinger pair production in 1+1 dimensional de Sitter space, filled with a constant electric field E. This can be thought of as a model for describing false vacuum decay beyond the semiclassical approximation, where pairs of a quantum field φ of mass m and charge e play the role of vacuum bubbles. We find that the adiabatic ''in'' vacuum associated with the flat chart develops a space-like expectation value for the current J, which manifestly breaks the de Sitter invariance of the background fields. We derive a simple expression for J(E), showing that both ''upward'' and ''downward'' tunneling contribute to the build-up of the current. For heavy fields, with m{sup 2} >> eE,H{sup 2}, the current is exponentially suppressed, in agreement with the results of semiclassical instanton methods. Here, H is the inverse de Sitter radius. On the other hand, light fields with m || H lead to a phenomenon of infrared hyperconductivity, where a very small electric field mH∼
Matter-coupled de Sitter supergravity
NASA Astrophysics Data System (ADS)
Kallosh, R. E.
2016-05-01
The de Sitter supergravity describes the interaction of supergravity with general chiral and vector multiplets and also one nilpotent chiral multiplet. The extra universal positive term in the potential, generated by the nilpotent multiplet and corresponding to the anti-D3 brane in string theory, is responsible for the de Sitter vacuum stability in these supergravity models. In the flat-space limit, these supergravity models include the Volkov-Akulov model with a nonlinearly realized supersymmetry. We generalize the rules for constructing the pure de Sitter supergravity action to the case of models containing other matter multiplets. We describe a method for deriving the closed-form general supergravity action with a given potential K, superpotential W, and vectormatrix fAB interacting with a nilpotent chiral multiplet. It has the potential V = eK(|F2|+|DW|2-3|W|2), where F is the auxiliary field of the nilpotent multiplet and is necessarily nonzero. The de Sitter vacuums are present under the simple condition that |F2|-3|W|2 > 0. We present an explicit form of the complete action in the unitary gauge.
5D supergravity and projective superspace
NASA Astrophysics Data System (ADS)
Kuzenko, Sergei M.; Tartaglino-Mazzucchelli, Gabriele
2008-02-01
This paper is a companion to our earlier work [1] in which the projective superspace formulation for matter-coupled simple supergravity in five dimensions was presented. For the minimal multiplet of 5D Script N = 1 supergravity introduced by Howe in 1981, we give a complete solution of the Bianchi identities. The geometry of curved superspace is shown to allow the existence of a large family of off-shell supermultiplets that can be used to describe supersymmetric matter, including vector multiplets and hypermultiplets. We formulate a manifestly locally supersymmetric action principle. Its natural property turns out to be the invariance under so-called projective transformations of the auxiliary isotwistor variables. We then demonstrate that the projective invariance allows one to uniquely restore the action functional in a Wess-Zumino gauge. The latter action is well-suited for reducing the supergravity-matter systems to components.
NASA Astrophysics Data System (ADS)
Cicoli, Michele; Quevedo, Fernando; Valandro, Roberto
2016-03-01
Hidden sector D7-branes with non-zero gauge flux are a generic feature of type IIB compactifications. A non-vanishing Fayet-Iliopoulos term induced by non-zero gauge flux leads to a T-brane configuration. Expanding the D7-brane action around this T-brane background in the presence of three-form supersymmetry breaking fluxes, we obtain a positive definite contribution to the moduli scalar potential which can be used as an uplifting source for de Sitter vacua. In this way we provide a higher-dimensional understanding of known 4D mechanisms of de Sitter uplifting based on hidden sector F-terms which are non-zero because of D-term stabilisation.
Horizon complementarity in elliptic de Sitter space
NASA Astrophysics Data System (ADS)
Hackl, Lucas; Neiman, Yasha
2015-02-01
We study a quantum field in elliptic de Sitter space dS4/Z2—the spacetime obtained from identifying antipodal points in dS4. We find that the operator algebra and Hilbert space cannot be defined for the entire space, but only for observable causal patches. This makes the system into an explicit realization of the horizon complementarity principle. In the absence of a global quantum theory, we propose a recipe for translating operators and states between observers. This translation involves information loss, in accordance with the fact that two observers see different patches of the spacetime. As a check, we recover the thermal state at the de Sitter temperature as a state that appears the same to all observers. This thermal state arises from the same functional that, in ordinary dS4, describes the Bunch-Davies vacuum.
Quantum Dynamics for de Sitter Radiation
NASA Astrophysics Data System (ADS)
Kim, Sang Pyo
2012-02-01
We revisit the Hamiltonian formalism for a massive scalar field and study the particle production in a de Sitter space. In the invariant-operator picture the time-dependent annihilation and creation operators are constructed in terms of a complex solution to the classical equation of motion for the field and the Gaussian wave function for each Fourier mode is found which is an exact solution to the Schrödinger equation. The in-out formalism is reformulated by the annihilation and creation operators and the Gaussian wave functions. The de Sitter radiation from the in-out formalism differs from the Gibbons-Hawking radiation in the planar coordinates, and we discuss the discrepancy of the particle production by the two methods.
De Sitter's theory of Galilean satellites
NASA Astrophysics Data System (ADS)
Broer, Henk; Zhao, Lei
2016-08-01
In this article, we investigate the mathematical part of De Sitter's theory on the Galilean satellites, and further extend this theory by showing the existence of some quasi-periodic librating orbits by application of KAM theorems. After showing the existence of De Sitter's family of linearly stable periodic orbits in the Jupiter-Io-Europa-Ganymede model by averaging and reduction techniques in the Hamiltonian framework, we further discuss the possible extension of this theory to include a fourth satellite Callisto, and establish the existence of a set of positive measure of quasi-periodic librating orbits in both models for almost all choices of masses among which one sufficiently dominates the others.
Quantum statistical entropy of Schwarzchild-de Sitter spacetime
NASA Astrophysics Data System (ADS)
Zhao, Ren; Zhang, Li-Chun; Zhao, Hui-Hua
2012-10-01
Using the quantum statistical method, we calculate quantum statistical entropy between the black hole horizon and the cosmological horizon in Schwarzchild spacetime and derive the expression of quantum statistical entropy in de Sitter spacetime. Under the Unruh-Verlinde temperature of Schwarzchild-de Sitter spacetime in the entropic force views, we obtain the expression of quantum statistical entropy in de Sitter spacetime. It is shown that in de Sitter spacetime quantum statistical entropy is the sum of thermodynamic entropy corresponding black hole horizon and the one corresponding cosmological horizon. And the correction term of de Sitter spacetime entropy is obtained. Therefore, it is confirmed that the black hole entropy is the entropy of quantum field outside the black hole horizon. The entropy of de Sitter spacetime is the entropy of quantum field between the black hole horizon and the cosmological horizon.
De Sitter Space Without Dynamical Quantum Fluctuations
NASA Astrophysics Data System (ADS)
Boddy, Kimberly K.; Carroll, Sean M.; Pollack, Jason
2016-06-01
We argue that, under certain plausible assumptions, de Sitter space settles into a quiescent vacuum in which there are no dynamical quantum fluctuations. Such fluctuations require either an evolving microstate, or time-dependent histories of out-of-equilibrium recording devices, which we argue are absent in stationary states. For a massive scalar field in a fixed de Sitter background, the cosmic no-hair theorem implies that the state of the patch approaches the vacuum, where there are no fluctuations. We argue that an analogous conclusion holds whenever a patch of de Sitter is embedded in a larger theory with an infinite-dimensional Hilbert space, including semiclassical quantum gravity with false vacua or complementarity in theories with at least one Minkowski vacuum. This reasoning provides an escape from the Boltzmann brain problem in such theories. It also implies that vacuum states do not uptunnel to higher-energy vacua and that perturbations do not decohere while slow-roll inflation occurs, suggesting that eternal inflation is much less common than often supposed. On the other hand, if a de Sitter patch is a closed system with a finite-dimensional Hilbert space, there will be Poincaré recurrences and dynamical Boltzmann fluctuations into lower-entropy states. Our analysis does not alter the conventional understanding of the origin of density fluctuations from primordial inflation, since reheating naturally generates a high-entropy environment and leads to decoherence, nor does it affect the existence of non-dynamical vacuum fluctuations such as those that give rise to the Casimir effect.
De Sitter Space Without Dynamical Quantum Fluctuations
NASA Astrophysics Data System (ADS)
Boddy, Kimberly K.; Carroll, Sean M.; Pollack, Jason
2016-03-01
We argue that, under certain plausible assumptions, de Sitter space settles into a quiescent vacuum in which there are no dynamical quantum fluctuations. Such fluctuations require either an evolving microstate, or time-dependent histories of out-of-equilibrium recording devices, which we argue are absent in stationary states. For a massive scalar field in a fixed de Sitter background, the cosmic no-hair theorem implies that the state of the patch approaches the vacuum, where there are no fluctuations. We argue that an analogous conclusion holds whenever a patch of de Sitter is embedded in a larger theory with an infinite-dimensional Hilbert space, including semiclassical quantum gravity with false vacua or complementarity in theories with at least one Minkowski vacuum. This reasoning provides an escape from the Boltzmann brain problem in such theories. It also implies that vacuum states do not uptunnel to higher-energy vacua and that perturbations do not decohere while slow-roll inflation occurs, suggesting that eternal inflation is much less common than often supposed. On the other hand, if a de Sitter patch is a closed system with a finite-dimensional Hilbert space, there will be Poincaré recurrences and dynamical Boltzmann fluctuations into lower-entropy states. Our analysis does not alter the conventional understanding of the origin of density fluctuations from primordial inflation, since reheating naturally generates a high-entropy environment and leads to decoherence, nor does it affect the existence of non-dynamical vacuum fluctuations such as those that give rise to the Casimir effect.
Compactifying de Sitter space naturally selects a small cosmological constant
NASA Astrophysics Data System (ADS)
Brown, Adam R.; Dahlen, Alex; Masoumi, Ali
2014-12-01
We study compactifications of D -dimensional de Sitter space with a q -form flux down to D -N q dimensions. We show that for (N -1 )(q -1 )≥2 there are double-exponentially or even infinitely many compact de Sitter vacua, and that their effective cosmological constants accumulate at zero. This population explosion of Λ ≪1 de Sitters arises by a mechanism analogous to natural selection.
The Role of Sitters in Delirium: an Update
Carr, Frances M.
2013-01-01
Purpose The concept behind constant observation is not new. Whilst traditionally performed by nursing staff, it is now commonly performed by sitters. Details surrounding the usage, job description, training, clinical and cost effectiveness of sitters are not known; hence the reason for this review. Methods A literature search was performed in MEDLINE, Cochrane Database of Systematic Reviews, and PubMed from the years 1960 to October 2011. The definition for sitter used in the articles was accepted for this review. Results From this review, it is evident that sitters are being employed in a variety of settings. The question of which type of person would provide the most benefit in the sitter role is still not clear; whilst sitters have typically included family and volunteers, it may be trained volunteers who may offer the most cost-effective solution. The paucity of information available regarding the training and assessments of sitters and the lack of formal guidelines regulating sitters’ use results in a lack of information available regarding these sitters, and current available evidence is conflicting regarding the benefits in terms of cost and clinical outcome. The only strong evidence relating to clinical benefit comes from the use of fully-trained sitters as part of a multi-interventional program (i.e., HELP) Conclusions Current evidence supports a role for the sitter as part of the management of patients with delirium. The most cost-effective sitter role appears to be trained volunteers. Further research is needed to determine the specific type of training required for the sitter role. The creation of a national set of regulations or guidelines would provide safeguards in the industry to ensure safe and effective patient care. PMID:23440038
NASA Astrophysics Data System (ADS)
Azarov, Vladimir I.; Gayasov, Robert R.
2016-03-01
The spectrum of three times ionized platinum, Pt IV, was investigated in the 530-1800 Å wavelength region. The analysis has resulted in the determination of the 5d7, 5d66s and 5d66p configurations. Seventeen of 19 theoretically possible 5d7 levels, 58 of 63 possible 5d66s levels and 162 of 180 possible 5d66p levels have been established. The levels are based on 1478 classified spectral lines. The level structure and transition probabilities were calculated by means of the orthogonal operators method. The energy parameters have been determined by the least squares fit to the observed levels. Calculated energy values and LS-compositions, as well as gA values obtained from the fitted parameter values are presented.
A new vacuum state in de Sitter space
NASA Astrophysics Data System (ADS)
Pfautsch, Jonathan D.
1982-11-01
We present a new vacuum state which can be defined in a region of de Sitter space. This region corresponds to a K=-1 Robertson-Walker coordinatization of de Sitter space. The renormalized expectation value of the stress tensor for the conformally invariant massless scalar field in this vacuum is evaluated, and is found to differ from the corresponding result in the usual de Sitter-invariant vacuum by the absence of a pure radiation term. We also indicate that this can be accounted for by regarding the de Sitter-invariant vacuum as a thermal state relative to the new vacuum.
Large-scale structure challenges dilaton gravity in a 5D brane scenario with AdS bulk
NASA Astrophysics Data System (ADS)
Konikowska, Dominika
2014-02-01
We study a theory of dilaton gravity in a five-dimensional brane scenario, with a non-minimal coupling of the dilaton to the matter content of the universe localized on the brane. The effective gravitational equations at the brane are derived in the Einstein frame in the covariant approach, addressing certain misconceptions in the literature. We then investigate whether the observed large-scale structure of the universe can exist on the brane in this dilaton gravity scenario with an exact anti de Sitter bulk, assuming that the matter energy-momentum tensor has the form of an inhomogeneous perfect fluid. The corresponding constraint on the spatial derivative of the matter energy density is derived, and subsequently quantified using the current limits resulting from searches for variation of the Newton's constant. By confronting it with the observational data from galaxy surveys, we show that up to scales of the order of 104 Mpc, the derived bound on the spatial derivative of the matter energy density does not allow for the existence of the large-scale structure as observed today. Thus, such a dilaton gravity brane scenario is ruled out.
Inflation Driven by q-de Sitter
NASA Astrophysics Data System (ADS)
Setare, M. R.; Momeni, D.; Kamali, V.; Myrzakulov, R.
2016-02-01
We propose a generalised de Sitter scale factor for the cosmology of early and late time universe, including single scalar field is called as inflaton. This form of scale factor has a free parameter q is called as nonextensivity parameter. When q = 1, the scale factor is de Sitter. This scale factor is an intermediate form between power-law and de Sitter. We study cosmology of such families. We show that both kinds of dark components, dark energy and dark matter simultaneously are described by this family of solutions. As a motivated idea, we investigate inflation in the framework of q-de Sitter. We consider three types of scenarios for inflation. In a single inflation scenario, we observe that, inflation ended without any specific ending inflation ϕ e n d , the spectral index and the associated running of the spectral index are n s - 1 ˜ -2 𝜖, α s ≡ 0. To end the inflation: we should have q={3}/{4}. We deduce that the inflation ends when the evolution of the scale factor is a( t) = e 3/4( t). With this scale factor there is no need to specify ϕ e n d . As an alternative to have inflation with ending point, We will study q-inflation model in the context of warm inflation. We propose two forms of damping term Γ. In the first case when Γ = Γ0, we show the scale invariant spectrum, (Harrison-Zeldovich spectrum, i.e. n s = 1) may be approximately presented by (q={9}/{10}, ~N=70). Also there is a range of values of R and n s which is compatible with the BICEP2 data where q={9}/{10}. In case Γ = Γ1 V( ϕ), it is observed that small values of a number of e-folds are assured for small values of q parameter. Also in this case, the scale-invariant spectrum may be represented by (q,N) = ({9}/{10},70). For q={9}/{10} a range of values of R and n s is compatible with the BICEP2 data. Consequently, the proposal of q-de Sitter is consistent with observational data. We observe that the non-extensivity parameter q plays a significant role in inflationary scenario.
4D spacetimes embedded in 5D light-like Kasner universes
NASA Astrophysics Data System (ADS)
Ponce de Leon, J.
2009-09-01
We consider spatially homogeneous, anisotropic cosmological models in 5D whose line element can be written as dS^2 = {\\cal {A}}(u, v)\\,du \\,dv - {\\cal {B}}_{i j}(u, v)\\,dx^{i}\\,dx^{j}, (i, j = 1, 2, 3), where u and v are light-like coordinates. In the case where {\\cal {B}}_{i j} is diagonal, we construct three families of analytic solutions to the 5D vacuum field equations RAB = 0 (A, B = 0, 1, 2, 3, 4). Among them, there is a family of self-similar homothetic solutions that contains, as a particular case, the so-called light-like Kasner universes. In this work, we provide a detailed study of the different types of 4D scenarios that can be embedded in such universes. For the sake of generality of the discussion, and applicability of the results, in our analysis we consider the two versions of non-compactified 5D relativity in vogue, namely braneworld theory and induced matter theory. We find a great variety of cosmological models in 4D which are anisotropic versions of the FRW ones. We obtain models on the brane with a non-vanishing cosmological term Λ(4), which inflate à la de Sitter without satisfying the classical false-vacuum equation of state. Using the symmetry of the solutions, we construct a class of non-static vacuum solutions on the brane. We also develop static pancake-like distributions where the matter is concentrated in a thin surface (near z = 0), similar to those proposed by Zel'dovich for the shape of the first collapsed objects in an expanding anisotropic universe. The solutions discussed here can be applied in a variety of physical situations.
Generalized elastica on 2-dimensional de Sitter space S12
NASA Astrophysics Data System (ADS)
Huang, Rongpei; Yu, Junyan
2016-02-01
In this paper, the extremals of curvature energy actions on non-null regular curves in 2-dimensional de Sitter space are studied. We completely solve the Euler-Lagrange equation by quadratures. By using the Killing field, we construct three special coordinate systems and express the generalized elastica in 2-dimensional de Sitter space S12 by integral explicitly.
Dirac oscillator and nonrelativistic Snyder-de Sitter algebra
Stetsko, M. M. E-mail: mykola@ktf.franko.lviv.ua
2015-01-15
Three dimensional Dirac oscillator was considered in space with deformed commutation relations known as Snyder-de Sitter algebra. Snyder-de Sitter commutation relations give rise to appearance of minimal uncertainties in position as well as in momentum. To derive energy spectrum and wavefunctions of the Dirac oscillator, supersymmetric quantum mechanics and shape invariance technique were applied.
Dirac oscillator and nonrelativistic Snyder-de Sitter algebra
NASA Astrophysics Data System (ADS)
Stetsko, M. M.
2015-01-01
Three dimensional Dirac oscillator was considered in space with deformed commutation relations known as Snyder-de Sitter algebra. Snyder-de Sitter commutation relations give rise to appearance of minimal uncertainties in position as well as in momentum. To derive energy spectrum and wavefunctions of the Dirac oscillator, supersymmetric quantum mechanics and shape invariance technique were applied.
Discrete symmetries and de Sitter spacetime
Cotăescu, Ion I. Pascu, Gabriel
2014-11-24
Aspects of the ambiguity in defining quantum modes on de Sitter spacetime using a commuting system composed only of differential operators are discussed. Discrete symmetries and their actions on the wavefunction in commonly used coordinate charts are reviewed. It is argued that the system of commuting operators can be supplemented by requiring the invariance of the wavefunction to combined discrete symmetries- a criterion which selects a single state out of the α-vacuum family. Two such members of this family are singled out by particular combined discrete symmetries- states between which exists a well-known thermality relation.
De Sitter uplift with Dynamical Susy Breaking
NASA Astrophysics Data System (ADS)
Retolaza, Ander; Uranga, Angel
2016-04-01
We propose the use of D-brane realizations of Dynamical Supersymmetry Breaking (DSB) gauge sectors as sources of uplift in compactifications with moduli stabilization onto de Sitter vacua. This construction is fairly different from the introduction of anti D-branes, yet allows for tunably small contributions to the vacuum energy via their embedding into warped throats. The idea is explicitly exemplified by the embedding of the 1-family SU(5) DSB model in a local warped throat with fluxes, which we discuss in detail in terms of orientifolds of dimer diagrams.
Constraining de Sitter Space in String Theory.
Kutasov, David; Maxfield, Travis; Melnikov, Ilarion; Sethi, Savdeep
2015-08-14
We argue that the heterotic string does not have classical vacua corresponding to de Sitter space-times of dimension four or higher. The same conclusion applies to type II vacua in the absence of Ramond-Ramond fluxes. Our argument extends prior supergravity no-go results to regimes of high curvature. We discuss the interpretation of the heterotic result from the perspective of dual type II orientifold constructions. Our result suggests that the genericity arguments used in string landscape discussions should be viewed with caution. PMID:26317710
de Sitter Vacua via Consistent D Terms
Villadoro, Giovanni; Zwirner, Fabio
2005-12-02
We introduce a new mechanism for producing locally stable de Sitter or Minkowski vacua, with spontaneously broken N=1 supersymmetry and no massless scalars, applicable to superstring and M-theory compactifications with fluxes. We illustrate the mechanism with a simple N=1 supergravity model that provides parametric control on the sign and the size of the vacuum energy. The crucial ingredient is a gauged U(1) that involves both an axionic shift and an R symmetry, and severely constrains the F- and D-term contributions to the potential.
de Sitter vacua via consistent terms.
Villadoro, Giovanni; Zwirner, Fabio
2005-12-01
We introduce a new mechanism for producing locally stable de Sitter or Minkowski vacua, with spontaneously broken N = 1 supersymmetry and no massless scalars, applicable to superstring and M-theory compactifications with fluxes. We illustrate the mechanism with a simple N = 1 supergravity model that provides parametric control on the sign and the size of the vacuum energy. The crucial ingredient is a gauged U(1) that involves both an axionic shift and an R symmetry, and severely constrains the F- and D-term contributions to the potential. PMID:16384294
Gravitational waves in a de Sitter universe
NASA Astrophysics Data System (ADS)
Bishop, Nigel T.
2016-02-01
The construction of exact linearized solutions to the Einstein equations within the Bondi-Sachs formalism is extended to the case of linearization about de Sitter spacetime. The gravitational wave field measured by distant observers is constructed, leading to a determination of the energy measured by such observers. It is found that gravitational wave energy conservation does not normally apply to inertial observers but that it can be formulated for a class of accelerated observers, i.e., with worldlines that are timelike but not geodesic.
Graviton propagator in a general invariant gauge on de Sitter
Mora, P. J.; Woodard, R. P.; Tsamis, N. C.
2012-12-15
We construct the graviton propagator on de Sitter background in the one parameter family of exact, de Sitter invariant gauges. Our result takes the form of a universal spin two part and a gauge dependent spin zero part. Scalar equations are derived for the structure functions of each part. There is no de Sitter invariant solution for either structure function, although the de Sitter breaking contribution to the spin zero part may drop out for certain choices of the gauge parameter. Our results imply that de Sitter breaking is universal for the graviton propagator, and hence that there is an error in the contrary results derived by analytic continuation of average gauge fixing techniques.
Nekrasov-Shatashvili limit of the 5D superconformal index
NASA Astrophysics Data System (ADS)
Papageorgakis, Constantinos; Pini, Alessandro; Rodríguez-Gómez, Diego
2016-08-01
We consider the Nekrasov-Shatashvili limit of the five-dimensional (5D) superconformal index and propose a novel prescription for selecting the finite contributions. Applying the latter to various examples of U(1) theories, we find that the 5D Nekrasov-Shatashvili index can be reproduced using recent techniques of Córdova and Shao, who related the 4D Schur index to the Bogomol'nyi-Prasad-Sommerfield (BPS) spectrum of the theory on the Coulomb branch. In this picture, the 5D instanton solitons are interpreted as additional flavor nodes in an associated 5D BPS quiver.
NASA Astrophysics Data System (ADS)
Wang, Chun-Xiao; Liu, Mo-Lin; Liu, Hong-Ya
2008-10-01
As one exact candidate of the higher dimensional black hole, the 5D Ricci Qat Schwarzschild-de Sitter black string space presents something interesting. In this paper, we give a numerical solution to the real scalar field around the Nariai black hole by the polynomial approximation. Unlike the previous tangent approximation, this fitting function makes a perfect match in the leading intermediate region and gives a good description near both the event and the cosmological horizons. We can read from our results that the wave is close to a harmonic one with the tortoise coordinate. Furthermore, with the actual radial coordinate the waves pile up almost equally near the both horizons.
NASA Astrophysics Data System (ADS)
Reyes, L. M.; Madriz Aguilar, J. E.; Bellini, M.
2011-06-01
We develop a stochastic approach to study scalar-field fluctuations of the inflaton field in an early inflationary universe with a black hole (BH), which is described by an effective 4D Schwarzschild-de Sitter (SdS) metric. This effective 4D metric is the induced metric on a 4D hypersurface, here representing our universe, which is obtained from a 5D Ricci-flat SdS static metric, after implementing a planar coordinate transformation. On this background, we found that at the end of the inflation, the squared fluctuations of the inflaton field are not exactly scale independent and result sensitive to the mass of the BH.
Liu Molin; Gui Yuanxing; Liu Hongya
2008-12-15
In this paper, we study the quantum statistical entropy in a 5D Ricci-flat black string solution, which contains a 4D Schwarzschild-de Sitter black hole on the brane, by using the improved thin-layer method with the generalized uncertainty principle. The entropy is the linear sum of the areas of the event horizon and the cosmological horizon without any cutoff and any constraint on the bulk's configuration rather than the usual uncertainty principle. The system's density of state and free energy are convergent in the neighborhood of horizon. The small-mass approximation is determined by the asymptotic behavior of metric function near horizons. Meanwhile, we obtain the minimal length of the position {delta}x, which is restrained by the surface gravities and the thickness of layer near horizons.
Gravitational waves during inflation from a 5D large-scale repulsive gravity model
NASA Astrophysics Data System (ADS)
Reyes, Luz M.; Moreno, Claudia; Madriz Aguilar, José Edgar; Bellini, Mauricio
2012-10-01
We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during the early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de Sitter metric on cosmological scales. This metric is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that it is possible to derive the dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity-antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.
The critical phenomena of charged rotating de Sitter black holes
NASA Astrophysics Data System (ADS)
Guo, Xiongying; Li, Huaifan; Zhang, Lichun; Zhao, Ren
2016-07-01
In this paper, we investigate the effective thermodynamic quantities in Kerr–Newman–de Sitter spacetime by considering the relations between the black hole event horizon and the cosmological event horizon. We find the effect of the critical point of Kerr–Newman–de Sitter spacetime for the different state parameters. We study the critical phenomena of the system taking different state parameters. This result is consistent with the nature of a liquid–gas phase transition at the critical point, hence deepening the understanding of the analogy of charged de Sitter spacetime and liquid–gas systems.
de Sitter symmetry of Neveu-Schwarz spinors
NASA Astrophysics Data System (ADS)
Epstein, Henri; Moschella, Ugo
2016-05-01
We study the relations between Dirac fields living on the 2-dimensional Lorentzian cylinder and the ones living on the double-covering of the 2-dimensional de Sitter manifold, here identified as a certain coset space of the group SL(2 , R). We show that there is an extended notion of de Sitter covariance only for Dirac fields having the Neveu-Schwarz anti-periodicity and construct the relevant cocycle. Finally, we show that the de Sitter symmetry is naturally inherited by the Neveu-Schwarz massless Dirac field on the cylinder.
Neutrino Tunneling from NUT Kerr Newman de Sitter Black Hole
NASA Astrophysics Data System (ADS)
Yang, Nan; Yang, Juan; Li, Jin
2013-08-01
In this paper, the method of semi-classical is applied to explore the Hawking radiation of a NUT-Kerr-Newman de Sitter Black Hole from tunneling point of view. The Hamilton-Jacobi equation in NUT-Kerr-Newman de Sitter space time is derived by the method presented by Lin and Yang (Chin. Phys. B, 20:110403, 2011). We obtain the Hawking temperatures at the event horizon and cosmological horizon and we also obtain the tunneling probability of neutrino following the semi-classical quantum equation. The results show the common features of NUT-Kerr-Newman de Sitter Black Hole.
NASA Astrophysics Data System (ADS)
Chen, Xiang
2012-11-01
We investigate the net force on a rigid Casimir cavity generated by vacuum fluctuations of electromagnetic field in three cases: de Sitter space-time, de Sitter space-time with weak gravitational field and Schwarzschild-de Sitter space-time. In de Sitter space-time the resulting net force follows the square inverse law but unfortunately it is too weak to be measurable due to the large universe radius. By introducing a weak gravitational field into the de Sitter space-time, we find that the net force can now be split into two parts, one is the gravitational force due to the induced effective mass between the two plates and the other one is generated by the metric structure of de Sitter space-time. In order to investigate the vacuum fluctuation force on the rigid cavity under strong gravitational field, we perform a similar analysis in Schwarzschild-de Sitter space-time and results are obtained in three different limits. The most interesting one is when the cavity gets closer to the horizon of a blackhole, square inverse law is recovered and the repulsive force due to negative energy/mass of the cavity now has an observable strength. More importantly the force changes from being repulsive to attractive when the cavity crosses the event horizon, so that the energy/mass of the cavity switches the sign, which suggests the unusual time direction inside the event horizon.
Gravitational waves in open de Sitter space
NASA Astrophysics Data System (ADS)
Hawking, S. W.; Hertog, Thomas; Turok, Neil
2000-09-01
We compute the spectrum of primordial gravitational wave perturbations in open de Sitter spacetime. The background spacetime is taken to be the continuation of an O(5) symmetric instanton saddle point of the Euclidean no boundary path integral. The two-point tensor fluctuations are computed directly from the Euclidean path integral. The Euclidean correlator is then analytically continued into the Lorentzian region where it describes the quantum mechanical vacuum fluctuations of the graviton field. Unlike the results of earlier work, the correlator is shown to be unique and well behaved in the infrared. We show that the infrared divergence found in previous calculations is due to the contribution of a discrete gauge mode inadvertently included in the spectrum.
Ghost inflation and de Sitter entropy
NASA Astrophysics Data System (ADS)
Jazayeri, Sadra; Mukohyama, Shinji; Saitou, Rio; Watanabe, Yota
2016-08-01
In the setup of ghost condensation model the generalized second law of black hole thermodynamics can be respected under a radiatively stable assumption that couplings between the field responsible for ghost condensate and matter fields such as those in the Standard Model are suppressed by the Planck scale. Since not only black holes but also cosmology are expected to play important roles towards our better understanding of gravity, we consider a cosmological setup to test the theory of ghost condensation. In particular we shall show that the de Sitter entropy bound proposed by Arkani-Hamed, et al. is satisfied if ghost inflation happened in the early epoch of our universe and if there remains a tiny positive cosmological constant in the future infinity. We then propose a notion of cosmological Page time after inflation.
Perdurance of multiply connected de Sitter space
NASA Astrophysics Data System (ADS)
González-Díaz, Pedro F.
1999-06-01
This paper deals with a study of the effects that spherically symmetric first-order metric perturbations and vacuum quantum fluctuations have on the stability of the multiply connected de Sitter spacetime recently proposed by Gott and Li. It is the main conclusion of this study that although such a spacetime is stable to the classical metric perturbations for any size of the nonchronal region, it is only stable against the quantum fluctuations of vacuum if the size of the multiply connected region is of the order of the Planck scale. Therefore, boundary conditions for the state of the universe based on the notion that the universe created itself in a regime where closed timelike curves were active and stable still appear to be physically and philosophically well supported as are those boundary conditions relying on the notion that the universe was created out of nothing.
On higher spin symmetries in de Sitter QFTs
NASA Astrophysics Data System (ADS)
Costa, Renato; Morrison, Ian A.
2016-03-01
We consider the consequences of global higher-spin symmetries in quantum field theories on a fixed de Sitter background of spacetime dimension D ≥ 3. These symmetries enhance the symmetry group associated with the isometries of the de Sitter background and thus strongly constrain the dynamics of the theory. In particular, we consider the case when a higher spin charge acts linearly on a scalar operator to leading order in a Fefferman-Graham expansion near the future/past conformal boundaries. We show that this implies that the expectation values of the operator inserted near the boundaries are asymptotically Gaussian. Thus, these operators have trivial cosmological spectra, and on global de Sitter these operators have only Gaussian correlations between operators inserted near future/past infinity. The latter result may be interpreted as an analogue of the Coleman-Mandula theorem for QFTs on de Sitter spacetime.
Breaking of de Sitter invariance in quantum cosmological gravity
NASA Astrophysics Data System (ADS)
Kleppe, Gary
1993-11-01
The effects of de Sitter transformations on linearized quantum gravity in a de Sitter space background are worked out explicitly. It is shown that the linearized solutions are closed under the transformations of the de Sitter group. To do this it is necessary to use a compensating gauge transformation to return the transformed solution to the original gauge. It is then shown that the form of the graviton propagator in this background, as found by Tsamis and Woodard, is not de Sitter invariant, and no suitable invariant propagator exists, even when gauge transformations which compensate for the noninvariant gauge choice are introduced. This leads us to conclude that the vacuum is not invariant. Address after 1 August 1993: Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487, USA.
q-vertex operator from 5D Nekrasov function
NASA Astrophysics Data System (ADS)
Itoyama, H.; Oota, T.; Yoshioka, R.
2016-08-01
The five-dimensional AGT correspondence implies the connection between the q-deformed Virasoro block and the 5d Nekrasov partition function. In this paper, we determine a q-deformation of the four-point block in the Coulomb gas representation from the 5d Nekrasov function, and obtain an expression of the q-deformed vertex operator. If we use only one kind of the q-vertex operators, one of the insertion points of them must be modified in order to hold the 2d/5d correspondence.
Yeh, Chih-Kuo; Song, Peng; Lin, Peng-Yen; Fu, Chi-Wing; Lin, Chao-Hung; Lee, Tong-Yee
2013-02-01
This paper introduces double-sided 2.5D graphics, aiming at enriching the visual appearance when manipulating conventional 2D graphical objects in 2.5D worlds. By attaching a back texture image on a single-sided 2D graphical object, we can enrich the surface and texture detail on 2D graphical objects and improve our visual experience when manipulating and animating them. A family of novel operations on 2.5D graphics, including rolling, twisting, and folding, are proposed in this work, allowing users to efficiently create compelling 2.5D visual effects. Very little effort is needed from the user's side. In our experiment, various creative designs on double-sided graphics were worked out by the recruited participants including a professional artist, which show and demonstrate the feasibility and applicability of our proposed method. PMID:22529328
Substitutional 4d and 5d impurities in graphene.
Alonso-Lanza, Tomás; Ayuela, Andrés; Aguilera-Granja, Faustino
2016-08-21
We describe the structural and electronic properties of graphene doped with substitutional impurities of 4d and 5d transition metals. The adsorption energies and distances for 4d and 5d metals in graphene show similar trends for the later groups in the periodic table, which are also well-known characteristics of 3d elements. However, along earlier groups the 4d impurities in graphene show very similar adsorption energies, distances and magnetic moments to the 5d ones, which can be related to the influence of the 4d and 5d lanthanide contraction. Surprisingly, within the manganese group, the total magnetic moment of 3 μB for manganese is reduced to 1 μB for technetium and rhenium. We find that compared with 3d elements, the larger size of the 4d and 5d elements causes a high degree of hybridization with the neighbouring carbon atoms, reducing spin splitting in the d levels. It seems that the magnetic adjustment of graphene could be significantly different if 4d or 5d impurities are used instead of 3d impurities. PMID:27439363
NASA Astrophysics Data System (ADS)
Baxter, J. Erik
2016-02-01
We investigate dyonic black hole and dyon solutions of four-dimensional 𝔰𝔲(N) Einstein-Yang-Mills theory with a negative cosmological constant. We derive a set of field equations in this case, and prove the existence of non-trivial solutions to these equations for any integer N, with 2N - 2 gauge degrees of freedom. We do this by showing that solutions exist locally at infinity, and at the event horizon for black holes and the origin for solitons. We then prove that we can patch these solutions together regularly into global solutions that can be integrated arbitrarily far into the asymptotic regime. Our main result is to show that dyonic solutions exist in open sets in the parameter space, and hence that we can find non-trivial dyonic solutions in a number of regimes whose magnetic gauge fields have no zeros, which is likely important to the stability of the solutions.
NASA Astrophysics Data System (ADS)
Ponce de Leon, J.
2008-03-01
In this paper we find the most general self-similar, homogeneous and isotropic, Ricci-flat cosmologies in 5D. These cosmologies show a number of interesting features: (i) the field equations allow a complete integration in terms of one arbitrary function of the similarity variable, and a free parameter; (ii) the three-dimensional spatial surfaces are flat; (iii) the extra dimension is spacelike; (iv) the general solution is Riemann-flat in 5D but curved in 4D, which means that an observer confined to 4D spacetime can relate this curvature to the presence of matter, as determined by the Einstein equations in 4D. We show that these cosmologies can be interpreted, or used, as 5D Riemann-flat embeddings for spatially flat FRW cosmologies in 4D. In this interpretation our universe arises as a topological separation from an empty 5D Minkowski space, as envisaged by Zeldovich.
Tachyons in classical de Sitter vacua
NASA Astrophysics Data System (ADS)
Junghans, Daniel
2016-06-01
We revisit the possibility of de Sitter vacua and slow-roll inflation in type II string theory at the level of the classical two-derivative supergravity approximation. Previous attempts at explicit constructions were plagued by ubiquitous tachyons with a large η parameter whose origin has not been fully understood so far. In this paper, we determine and explain the tachyons in two setups that are known to admit unstable dS critical points: an SU(3) structure compactification of massive type IIA with O6-planes and an SU(2) structure compactification of type IIB with O5/O7-planes. We explicitly show that the tachyons are always close to, but never fully aligned with the sgoldstino direction in the considered examples and argue that this behavior is explained by a generalized version of a no-go theorem by Covi et al, which holds in the presence of large mixing in the mass matrix between the sgoldstino and the orthogonal moduli. This observation may also provide a useful stability criterion for general dS vacua in supergravity and string theory.
General aspects of the de Sitter phase
NASA Astrophysics Data System (ADS)
Imponente, G.; Montani, G.
2005-10-01
We present a detailed discussion of the inflationary scenario in the context of inhomogeneous cosmologies. After a review of the fundamental features characterizing the inflationary model, as referred to a homogeneous and isotropic Universe, we develop a generalization in view of including small inhomogeneous corrections in the theory. A second step in our discussion is devoted to show that the inflationary scenario provides a valuable dynamical “bridge” between a generic Kasner-like regime and a homogeneous and isotropic Universe in the horizon scale. This result is achieved by solving the Hamilton-Jacobi equation for a Bianchi IX model in the presence of a cosmological space-dependent term. In this respect, we construct a quasi-isotropic inflationary solution based on the expansion of the Einstein equations up to first two orders of approximation, in which the isotropy of the Universe is due to the dominance of the scalar field kinetic term; the first order of approximation corresponds to the inhomogeneous corrections and is driven by the matter evolution. We show how such a quasi-isotropic solution contains a certain freedom in fixing the space functions involved in the problem. The main physical issue of this analysis corresponds to outline the impossibility for the classical origin of density perturbations, due to the exponential decay of the matter term during the de Sitter phase.
Charlotte Moore Sitterly: A Life of Spectroscopy
NASA Astrophysics Data System (ADS)
Rubin, Vera C.
2010-01-01
Dr. Charlotte Moore Sitterly was a scientist in an era when it was rare for a woman to have the opportunity to devote her life to forefront science. Following her graduation from Swarthmore College in 1920, she accepted a position at Princeton University as an assistant to Henry Norris Russell. In 1925 she started a study of the solar spectrum. She could then not know that she would devote much of her scientific career to gathering basic atomic data that are invaluable to the scientific community, even today. In 1931 she obtained a PhD degree at U. California, Berkeley, and returned to Princeton as a staff member of the Princeton University Observatory. In 1945 she moved to the National Bureau of Science (NBS), to supervise preparation of the widely used tables of atomic energy levels. Following the successful lunching (1946) of a V2 rocket to obtain the ultra violet spectrum of the sun, Moore started working with Richard Tousey and his group at the Naval Research Laboratory (NRL). Ultimately, they extended the solar spectrum down to 2200 angstroms. She continued her affiliations with NBS and NRL until her death in 1990. Charlotte Moore was rare scientist who devoted her career to obtaining accurate numbers, thus enabling the scientific community to open her tables and know that the data are accurate.
Thermal interpretation of infrared dynamics in de Sitter
NASA Astrophysics Data System (ADS)
Rigopoulos, Gerasimos
2016-07-01
The infrared dynamics of a light, minimally coupled scalar field in de Sitter spacetime with Ricci curvature R = 12H2, averaged over horizon sized regions of physical volume VH = (4π/3)(1/H)3, can be interpreted as Brownian motion in a medium with de Sitter temperature TDS = hbarH/2π. We demonstrate this by directly deriving the effective action of scalar field fluctuations with wavelengths larger than the de Sitter curvature radius and generalizing Starobinsky's seminal results on stochastic inflation. The effective action describes stochastic dynamics and the fluctuating force drives the field to an equilibrium characterized by a thermal Gibbs distribution at temperature TDS which corresponds to a de Sitter invariant state. Hence, approach towards this state can be interpreted as thermalization. We show that the stochastic kinetic energy of the coarse-grained description corresponds to the norm of ∂μphi and takes a well defined value per horizon volume ½langle(∇phi)2rangle = ‑ ½TDS/VH. This approach allows for the non-perturbative computation of the de Sitter invariant stress energy tensor langleTμνrangle for an arbitrary scalar potential.
Vacua and correlators in hyperbolic de Sitter space
NASA Astrophysics Data System (ADS)
Dimitrakopoulos, Fotios V.; Kabir, Laurens; Mosk, Benjamin; Parikh, Maulik; van der Schaar, Jan Pieter
2015-06-01
We study the power- and bi-spectrum of vacuum fluctuations in a hyperbolic section of de Sitter space, comparing two states of physical interest: the Bunch-Davies and hyperbolic vacuum. We introduce a one-parameter family of de Sitter hyperbolic sections and their natural vacua, and identify a limit in which it reduces to the planar section and the corresponding Bunch-Davies vacuum state. Selecting the Bunch-Davies vacuum for a massless scalar field implies a mixed reduced density matrix in a hyperbolic section of de Sitter space. We stress that in the Bunch-Davies state the hyperbolic de Sitter n-point correlation functions have to match the planar de Sitter n-point correlation functions. The expressions for the planar and hyperbolic Bunch-Davies correlation functions only appear different because of the transformation from planar to hyperbolic coordinates. Initial state induced deviations from the standard inflationary predictions are instead obtained by considering the pure hyperbolic vacuum, as we verify explicitly by computing the power- and bi-spectrum. For the bi-spectrum in the hyperbolic vacuum we find that the corrections as compared to the standard Bunch-Davies result are not enhanced in specific momentum configurations and strongly suppressed for momenta large compared to the hyperbolic curvature scale. We close with some final remarks, in particular regarding the implications of these results for more realistic inflationary bubble scenarios.
5D Tempest simulations of kinetic edge turbulence
NASA Astrophysics Data System (ADS)
Xu, X. Q.; Xiong, Z.; Cohen, B. I.; Cohen, R. H.; Dorr, M. R.; Hittinger, J. A.; Kerbel, G. D.; Nevins, W. M.; Rognlien, T. D.; Umansky, M. V.; Qin, H.
2006-10-01
Results are presented from the development and application of TEMPEST, a nonlinear five dimensional (3d2v) gyrokinetic continuum code. The simulation results and theoretical analysis include studies of H-mode edge plasma neoclassical transport and turbulence in real divertor geometry and its relationship to plasma flow generation with zero external momentum input, including the important orbit-squeezing effect due to the large electric field flow-shear in the edge. In order to extend the code to 5D, we have formulated a set of fully nonlinear electrostatic gyrokinetic equations and a fully nonlinear gyrokinetic Poisson's equation which is valid for both neoclassical and turbulence simulations. Our 5D gyrokinetic code is built on 4D version of Tempest neoclassical code with extension to a fifth dimension in binormal direction. The code is able to simulate either a full torus or a toroidal segment. Progress on performing 5D turbulence simulations will be reported.
2.5D dictionary learning based computed tomography reconstruction
NASA Astrophysics Data System (ADS)
Luo, Jiajia; Eri, Haneda; Can, Ali; Ramani, Sathish; Fu, Lin; De Man, Bruno
2016-05-01
A computationally efficient 2.5D dictionary learning (DL) algorithm is proposed and implemented in the model- based iterative reconstruction (MBIR) framework for low-dose CT reconstruction. MBIR is based on the minimization of a cost function containing data-fitting and regularization terms to control the trade-off between data-fidelity and image noise. Due to the strong denoising performance of DL, it has previously been considered as a regularizer in MBIR, and both 2D and 3D DL implementations are possible. Compared to the 2D case, 3D DL keeps more spatial information and generates images with better quality although it requires more computation. We propose a novel 2.5D DL scheme, which leverages the computational advantage of 2D-DL, while attempting to maintain reconstruction quality similar to 3D-DL. We demonstrate the effectiveness of this new 2.5D DL scheme for MBIR in low-dose CT. By applying the 2D DL method in three different orthogonal planes and calculating the sparse coefficients accordingly, much of the 3D spatial information can be preserved without incurring the computational penalty of the 3D DL method. For performance evaluation, we use baggage phantoms with different number of projection views. In order to quantitatively compare the performance of different algorithms, we use PSNR, SSIM and region based standard deviation to measure the noise level, and use the edge response to calculate the resolution. Experimental results with full view datasets show that the different DL based algorithms have similar performance and 2.5D DL has the best resolution. Results with sparse view datasets show that 2.5D DL outperforms both 2D and 3D DL in terms of noise reduction. We also compare the computational costs, and 2.5D DL shows strong advantage over 3D DL in both full-view and sparse-view cases.
Holography for a De Sitter-Esque geometry
NASA Astrophysics Data System (ADS)
Anninos, Dionysios; de Buyl, Sophie; Detournay, Stéphane
2011-05-01
Warped dS3 arises as a solution to topologically massive gravity (TMG) with positive cosmological constant +1/ ℓ 2 and Chern-Simons coefficient 1/ μ in the region μ 2 ℓ 2 < 27. It is given by a real line fibration over two-dimensional de Sitter space and is equivalent to the rotating Nariai geometry at fixed polar angle. We study the thermodynamic and asymptotic structure of a family of geometries with warped dS3 asymptotics. Interestingly, these solutions have both a cosmological horizon and an internal one, and their entropy is unbounded from above unlike black holes in regular de Sitter space. The asymptotic symmetry group resides at future infinity and is given by a semi-direct product of a Virasoro algebra and a current algebra. The right moving central charge vanishes when μ 2 ℓ 2 = 27/5. We discuss the possible holographic interpretation of these de Sitter-esque spacetimes.
Hawking's radiation in non-stationary rotating de Sitter background
NASA Astrophysics Data System (ADS)
Ibohal, N.; Ibungochouba, T.
2011-05-01
Hawking's radiation effect of Klein-Gordon scalar field, Dirac particles and Maxwell's electromagnetic field in the non-stationary rotating de Sitter cosmological space-time is investigated by using a method of generalized tortoise co-ordinates transformation. The locations and the temperatures of the cosmological horizons of the non-stationary rotating de Sitter model are derived. It is found that the locations and the temperatures of the rotating cosmological model depend not only on the time but also on the angle. The stress-energy regularization techniques are applied to the two dimensional analog of the de Sitter metrics and the calculated stress-energy tensor contains the thermal radiation effect.
Super-gauge field in de Sitter universe
NASA Astrophysics Data System (ADS)
Parsamehr, S.; Enayati, M.; Takook, M. V.
2016-05-01
The Gupta-Bleuler triplet for a vector-spinor gauge field is presented in the de Sitter ambient space formalism. The invariant space of field equation solutions is obtained with respect to an indecomposable representation of the de Sitter group. By using the general solution of the massless spin-3/2 field equation, the vector-spinor quantum field operator and its corresponding Fock space is constructed. The quantum field operator can be written in terms of the vector-spinor polarization states and a quantum conformally coupled massless scalar field, which is constructed on Bunch-Davies vacuum state. The two-point function is also presented, which is de Sitter covariant and analytic.
Localization Problem in the 5d Standing Wave Braneworld
NASA Astrophysics Data System (ADS)
Gogberashvili, Merab; Midodashvili, Pavle; Midodashvili, Levan
2012-10-01
We investigate the problem of pure gravitational localization of matter fields within the 5D standing wave braneworld generated by gravity coupled to a phantom-like scalar field. We show that in the case of increasing warp factor there exist normalizable zero modes of spin-0, -1/2, -1 and -2 fields on the brane.
Super-Hubble de Sitter fluctuations and the dynamical RG
NASA Astrophysics Data System (ADS)
Burgess, C. P.; Leblond, L.; Holman, R.; Shandera, S.
2010-03-01
Perturbative corrections to correlation functions for interacting theories in de Sitter spacetime often grow secularly with time, due to the properties of fluctuations on super-Hubble scales. This growth can lead to a breakdown of perturbation theory at late times. We argue that Dynamical Renormalization Group (DRG) techniques provide a convenient framework for interpreting and resumming these secularly growing terms. In the case of a massless scalar field in de Sitter with quartic self-interaction, the resummed result is also less singular in the infrared, in precisely the manner expected if a dynamical mass is generated. We compare this improved infrared behavior with large-N expansions when applicable.
(Anti-)evaporation of Schwarzschild-de Sitter black holes
NASA Astrophysics Data System (ADS)
Bousso, Raphael; Hawking, Stephen W.
1998-02-01
We study the quantum evolution of black holes immersed in a de Sitter background space. For black holes whose size is comparable to that of the cosmological horizon, this process differs significantly from the evaporation of asymptotically flat black holes. Our model includes the one-loop effective action in the s-wave and large N approximation. Black holes of the maximal mass are in equilibrium. Unexpectedly, we find that nearly maximal quantum Schwarzschild-de Sitter black holes anti-evaporate. However, there is a different perturbative mode that leads to evaporation. We show that this mode will always be excited when a pair of cosmological holes nucleates.
Smooth transitions from the Schwarzschild vacuum to de Sitter space
Conboy, Steven; Lake, Kayll
2005-06-15
We provide an infinity of spacetimes which contain part of both the Schwarzschild vacuum and de Sitter space. The transition, which occurs below the Schwarzschild event horizon, involves only boundary surfaces (no surface layers). An explicit example is given in which the weak and strong energy conditions are satisfied everywhere (except in the de Sitter section) and the dominant energy condition is violated only in the vicinity of the boundary to the Schwarzschild section. The singularity is avoided by way of a change in topology in accord with a theorem due to Borde.
ERIC Educational Resources Information Center
Jelsma, Jennifer
2010-01-01
The aim of this study was to investigate the performance of the recent EQ-5D-Y instrument compared with the standard EQ-5D in assessing the health-related quality of life of high school children in Cape Town. Either the EQ-5D or the EQ-5D-Y was given to high school children. The sample consisted of 521 respondents. The EQ-5D-Y was found to be…
How to use retarded Green's functions in de Sitter spacetime
Higuchi, Atsushi; Cheong, Lee Yen
2008-10-15
We demonstrate in examples that the covariant retarded Green's functions in electromagnetism and linearized gravity work as expected in de Sitter spacetime. We first clarify how retarded Green's functions should be used in spacetimes with spacelike past infinity such as de Sitter spacetime. In particular, we remind the reader of a general formula which gives the field for given initial data on a Cauchy surface and a given source (a charge or stress-energy tensor distribution) in its future. We then apply this formula to three examples: (i) electromagnetism in the future of a Cauchy surface in Minkowski spacetime, (ii) electromagnetism in de Sitter spacetime, and (iii) linearized gravity in de Sitter spacetime. In each example the field is reproduced correctly as predicted by the general argument. In the third example we construct a linearized gravitational field from two equal point masses located at the 'North and South Poles' which is nonsingular on the cosmological horizon and satisfies a covariant gauge condition and show that this field is reproduced by the retarded Green's function with corresponding gauge parameters.
Consistency of scalar potentials from quantum de Sitter space
NASA Astrophysics Data System (ADS)
Espinosa, José R.; Fortin, Jean-François; Trépanier, Maxime
2016-06-01
Consistency of the unconventional view of de Sitter space as a quantum theory of gravity with a finite number of degrees of freedom requires that Coleman-De Luccia tunneling rates to vacua with negative cosmological constant should be interpreted as recurrences to low-entropy states. This demand translates into two constraints, or consistency conditions, on the scalar potential that are generically as follows: (1) the distance in field space between the de Sitter vacuum and any other vacuum with negative cosmological constant must be of the order of the reduced Planck mass or larger and (2) the fourth root of the vacuum energy density of the de Sitter vacuum must be smaller than the fourth root of the typical scale of the scalar potential. These consistency conditions shed a different light on both outstanding hierarchy problems of the standard model of particle physics: the scale of electroweak symmetry breaking and the scale of the cosmological constant. Beyond the unconventional interpretation of quantum de Sitter space, we complete the analytic understanding of the thin-wall approximation of Coleman-De Luccia tunneling, extend its numerical analysis to generic potentials and discuss the role of gravity in stabilizing the standard model potential.
Snyder-de Sitter model from two-time physics
Carrisi, M. C.; Mignemi, S.
2010-11-15
We show that the symplectic structure of the Snyder model on a de Sitter background can be derived from two-time physics in seven dimensions and propose a Hamiltonian for a free particle consistent with the symmetries of the model.
Further investigations of the Kerr--de Sitter space
Khanal, U.
1985-08-15
Some recursion relations pertaining to the radial functions of Dirac, electromagnetic, and gravitational fields in the Kerr--de Sitter universe are proved. The behavior of the tortoise coordinate is investigated and it is shown that super radiance can also occur in this space.
Quantum Vacuum Instability of ``Eternal'' de Sitter Space
NASA Astrophysics Data System (ADS)
Mottola, Emil
2015-04-01
The Euclidean or Bunch-Davies state of quantum fields in global de Sitter space is shown to be unstable to small perturbations, even for a massive free field with no self-interactions. There are perturbations of this state with arbitrarily small energy density at early times that is exponentially blueshifted in the contracting phase of ``eternal'' de Sitter space, and becomes large enough to disturb the classical geometry through the semiclassical Einstein eqs. at later times. In the closely analogous case of a constant, uniform electric field, a time symmetric state equivalent to the de Sitter invariant one is constructed, which is also not a stable vacuum state under perturbations. The role of a quantum anomaly in the growth of perturbations and symmetry breaking is emphasized in both cases. The anomaly stress tensor shows that states invariant under the O(4) subgroup of the de Sitter group are also unstable to perturbations of lower spatial symmetry, implying that both the O(4) subgroup are broken by quantum fluctuations. Consequences of this result for cosmology and the problem of vacuum energy will be discussed.
Inflation in Non-de Sitter Background with Coherent States
NASA Astrophysics Data System (ADS)
Yusofi, E.; Mohsenzadeh, M.; M. R., Tanhayi
2016-03-01
We use the excited coherent states built over the initial non-de Sitter modes, to study the modification of spectra of primordial scalar fluctuation. Non-de Sitter modes are actually the asymptotic solution of the inflaton field equation [J. High Energy Phys. 09 (2014) 020]. We build excited coherent states over the non-de Sitter modes and despite the lack of interactions in the Lagrangian, we find a non-zero one-point function. It is shown that the primordial non-Gaussianity resulting from excited-de Sitter modes depend both of time and background space-time. It is very tiny of order (≤ 10-24), at the Planck initial fixed time that confirmed by resent observations for single field inflation but it grows in the present epoch. Moreover, our results at the leading order are similar to what obtained with general initial states and in the dS limit leads to standard results [J. Cosmol. Astropart. Phys. 1202 (2012) 005]. We will show that the non-dS modes and its resulting spectrum are more usable for far past time limit.
Macroscopicity and classicality of quantum fluctuations in de Sitter space
Wada, S.
1988-08-01
On the basis of the non-probabilistic interpretation of quantum mechanics, the authors define ''macroscopicity'' and ''classicality'' of quantum fluctuations as closely related but separate concepts. Then these properties are examined in quantum states (wave functions) of matter fields in de Sitter spacetime.
Macroscopicity and Classicality of Quantum Fluctuations in de Sitter Space
NASA Astrophysics Data System (ADS)
Wada, Sumio
On the basis of the non-probabilistic interpretation of quantum mechanics, we define “macroscopicity” and “classicality” of quantum fluctuations as closely related but separate concepts. Then these properties are examined in quantum states (wave functions) of matter fields in de Sitter spacetime.
Modular properties of full 5D SYM partition function
NASA Astrophysics Data System (ADS)
Qiu, Jian; Tizzano, Luigi; Winding, Jacob; Zabzine, Maxim
2016-03-01
We study properties of the full partition function for the U(1) 5D N = {2}^{ast } gauge theory with adjoint hypermultiplet of mass M . This theory is ultimately related to abelian 6D (2,0) theory. We construct the full non-perturbative partition function on toric Sasaki-Einstein manifolds by gluing flat copies of the Nekrasov partition function and we express the full partition function in terms of the generalized double elliptic gamma function G 2 C associated with a certain moment map cone C. The answer exhibits a curious SL(4 , ℤ) modular property. Finally, we propose a set of rules to construct the partition function that resembles the calculation of 5d supersymmetric partition function with the insert ion of defects of various co-dimensions.
A 5-D hyperchaotic Rikitake dynamo system with hidden attractors
NASA Astrophysics Data System (ADS)
Vaidyanathan, S.; Pham, V.-T.; Volos, C. K.
2015-07-01
This paper presents a 5-D hyperchaotic Rikitake dynamo system with three positive Lyapunov exponents which is derived by adding two state feedback controls to the famous 3-D Rikitake two-disk dynamo system. It is noted that the proposed hyperchaotic system has no equilibrium points and hence it exhibits hidden attractors. In addition, the qualitative properties, as well as the adaptive synchronization of the hyperchaotic Rikitake dynamo system with unknown system parameters, are discussed in details. The main results are proved using Lyapunov stability theory and numerical simulations are shown using MATLAB. Moreover, an electronic circuit realization in SPICE has been detailed to confirm the feasibility of the theoretical 5-D hyperchaotic Rikitake dynamo model.
Mapping the EQ-5D Index from the SF-12
Sullivan, Patrick W.; Ghushchyan, Vahram
2008-01-01
Background Previous mapping algorithms estimating EQ-5D index scores from the SF-12 were based on preferences from a UK community sample. However, preferences based on the general US population are most appropriate for cost-effectiveness analyses done from the societal perspective in the United States. Objective To provide a mapping algorithm for estimating EQ-5D index scores from the SF-12 based on a nationally representative sample and using preferences based on the general US population. Methods The Medical Expenditure Panel Survey (MEPS) 2002 and 2000 data were used as independent derivation and validation sets to estimate the relationship between SF-12 scores and EQ-5D index scores, controlling for sociodemographic characteristics and comorbidity burden. Prediction equations for end-users who only have access to SF-12 scores were derived and compared. The empirical performance of censored least absolute deviations (CLAD), Tobit, and ordinary least squares (OLS) analytic methods were compared by calculating the mean prediction error in the validation set. Results The fully specified CLAD model resulted in the lowest mean prediction error, followed by OLS and Tobit. The CLAD prediction equation based only on SF-12 scores performed better than the fully specified OLS and Tobit models. Conclusion The current research provides an algorithm for mapping EQ-5D index scores from the SF-12. This algorithm may provide analysts with an avenue to obtain appropriate preference-based health-related quality-of-life scores for use in cost-effectiveness analyses when only SF-12 data are available. PMID:16855128
Numerical Solutions in 5d Standing Wave Braneworld
NASA Astrophysics Data System (ADS)
Gogberashvili, Merab; Sakhelashvili, Otari; Tukhashvili, Giorgi
2013-06-01
Within the 5D standing wave braneworld model numerical solutions of the equations for matter fields with various spins are found. It is shown that corresponding action integrals are factorizable and convergent over the extra coordinate, i.e. 4D fields are localized on the brane. We find that only left massless fermions are localized on the brane, while the right fermions are localized in the bulk. We demonstrate also quantization of Kaluza-Klein excited modes in our model.
2.5D Cartoon Hair Modeling and Manipulation.
Yeh, Chih-Kuo; Jayaraman, Pradeep Kumar; Liu, Xiaopei; Fu, Chi-Wing; Lee, Tong-Yee
2015-03-01
This paper addresses a challenging single-view modeling and animation problem with cartoon images. Our goal is to model the hairs in a given cartoon image with consistent layering and occlusion, so that we can produce various visual effects from just a single image. We propose a novel 2.5D modeling approach to deal with this problem. Given an input image, we first segment the hairs of the cartoon character into regions of hair strands. Then, we apply our novel layering metric, which is derived from the Gestalt psychology, to automatically optimize the depth ordering among the hair strands. After that, we employ our hair completion method to fill the occluded part of each hair strand, and create a 2.5D model of the cartoon hair. By using this model, we can produce various visual effects, e.g., we develop a simplified fluid simulation model to produce wind blowing animations with the 2.5D hairs. To further demonstrate the applicability and versatility of our method, we compare our results with real cartoon hair animations, and also apply our model to produce a wide variety of hair manipulation effects, including hair editing and hair braiding. PMID:26357063
Heterogeneous 2.5D integration on through silicon interposer
NASA Astrophysics Data System (ADS)
Zhang, Xiaowu; Lin, Jong Kai; Wickramanayaka, Sunil; Zhang, Songbai; Weerasekera, Roshan; Dutta, Rahul; Chang, Ka Fai; Chui, King-Jien; Li, Hong Yu; Wee Ho, David Soon; Ding, Liang; Katti, Guruprasad; Bhattacharya, Suryanarayana; Kwong, Dim-Lee
2015-06-01
Driven by the need to reduce the power consumption of mobile devices, and servers/data centers, and yet continue to deliver improved performance and experience by the end consumer of digital data, the semiconductor industry is looking for new technologies for manufacturing integrated circuits (ICs). In this quest, power consumed in transferring data over copper interconnects is a sizeable portion that needs to be addressed now and continuing over the next few decades. 2.5D Through-Si-Interposer (TSI) is a strong candidate to deliver improved performance while consuming lower power than in previous generations of servers/data centers and mobile devices. These low-power/high-performance advantages are realized through achievement of high interconnect densities on the TSI (higher than ever seen on Printed Circuit Boards (PCBs) or organic substrates), and enabling heterogeneous integration on the TSI platform where individual ICs are assembled at close proximity (<1 mm separation) compared with several centimeters on a typical PCB. In this paper, we have outlined the benefits of adopting 2.5D TSI technology and also highlighted the current day approaches to implement this technology in Si fabrication facilities, and in assembly/packaging factories. While the systems and devices that power the mobile society benefit from exploiting advantages of 2.5D integration on TSI, there do exist surmountable challenges that need to be addressed for this relatively new technology to be used in high volume production of next generation semiconductor devices. The key areas of focus and challenges include: Technology planning and design-execution that are necessary for harnessing 2.5D TSI for building systems, processing flow for the fabrication of 100 μm thick TSI at acceptable costs, manufacturing flow for assembling multiple ICs on a 100 μm thick TSI in a repeatable, and reliable manner, thermo-mechanical analysis and optimization for addressing warpage issues, and thermal
Argentine Valuation of the EQ-5D Health States
Augustovski, Federico Ariel; Irazola, Vilma Edit; Velazquez, Alberto Pascual; Gibbons, Luz; Craig, Benjamin M.
2013-01-01
Objective To develop a set of EQ-5D health state values for the Argentine general population. Methods Consecutive subjects attending six primary care centers in Argentina were selected based on quota sampling and interviewed using the EuroQol Group protocol for measurement and valuation of health studies. Initially respondents were randomly assigned a unique card set; however, to improve efficiency, subjects were later randomly assigned to one of three fixed sets of EQ-5D states. Using the VAS and TTO responses for these states, we estimated a valuation model using ordinary least squares regression clustered by respondent. Predicted values for EQ-5D health states are compared to published values for the United States. Results Six hundred eleven subjects were interviewed by 14 trained interviewers, rendering 6,887 TTO and 6,892 VAS responses. The model had an R2 of 0.897 and 0.928 for TTO and VAS respectively. The mean absolute difference between observed and predicted values was 0.039 for TTO and 0.020 for VAS, each showing a Lin’s concordance coefficient above 0.98. United States and Argentine TTO predicted values were highly correlated (Pearson’s rho=0.963), though the average absolute difference was clinically meaningful (0.06), rejecting the US values for nearly two thirds of the states (62.8%). The Argentine population placed lower values on mild states and higher values on severe states. Conclusion This study provides an Argentine value set that could be used locally or regionally, with meaningful and significant differences with that of the US. Health policy in Latin America must incorporate local values for sovereignty and validity. PMID:19900257
Electromagnetic energy dispersion in a 5D universe
Hartnett, John G.
2010-06-15
Electromagnetism is analyzed in a 5D expanding universe. Compared to the usual 4D description of electrodynamics it can be viewed as adding effective charge and current densities to the universe that are static in time. These lead to effective polarization and magnetization of the vacuum, which is most significant at high redshift. Electromagnetic waves propagate but group and phase velocities are dispersive. This introduces a new energy scale to the cosmos. And as a result electromagnetic waves propagate with superluminal speeds but no energy is transmitted faster than the canonical speed of light c.
Perturbative charged rotating 5D Einstein-Maxwell black holes
NASA Astrophysics Data System (ADS)
Navarro-Lérida, Francisco
2010-12-01
We present perturbative charged rotating 5D Einstein-Maxwell black holes with spherical horizon topology. The electric charge Q is the perturbative parameter, the perturbations being performed up to 4th order. The expressions for the relevant physical properties of these black holes are given. The gyromagnetic ratio g, in particular, is explicitly shown to be non-constant in higher order, and thus to deviate from its lowest order value, g = 3. Comparison of the perturbative analytical solutions with their non-perturbative numerical counterparts shows remarkable agreement.
Electromagnetic energy dispersion in a 5D universe
NASA Astrophysics Data System (ADS)
Hartnett, John G.
2010-06-01
Electromagnetism is analyzed in a 5D expanding universe. Compared to the usual 4D description of electrodynamics it can be viewed as adding effective charge and current densities to the universe that are static in time. These lead to effective polarization and magnetization of the vacuum, which is most significant at high redshift. Electromagnetic waves propagate but group and phase velocities are dispersive. This introduces a new energy scale to the cosmos. And as a result electromagnetic waves propagate with superluminal speeds but no energy is transmitted faster than the canonical speed of light c.
NASA Astrophysics Data System (ADS)
Singh, Abhishek K.; Pandey, K. Priyabrat; Singh, Sunita; Kar, Supriya
2013-05-01
The U(1) gauge dynamics on a D 4-brane is revisited, with a two form, to construct an effective curvature theory in a second order formalism. We exploit the local degrees in a two form, and modify its dynamics in a gauge invariant way, to incorporate a non-perturbative metric fluctuation in an effective D 4-brane. Interestingly, the near horizon D 4-brane is shown to describe an asymptotic Anti de Sitter (AdS) in a semi-classical regime. Using Weyl scaling(s), we obtain the emergent rotating geometries leading to primordial de Sitter (dS) and AdS vacua in a quantum regime. Under a discrete transformation, we re-arrange the mixed dS patches to describe a Schwazschild-like dS (SdS) and a topological-like dS (TdS) black holes. We analyze SdS vacuum for Hawking radiations to arrive at Nariai geometry, where a discrete torsion forms a condensate. We perform thermal analysis to identify Nariai vacuum with a TdS. Investigation reveals an AdS patch within a thermal dS brane, which may provide a clue to unfold dS/CFT. In addition, the role of dark energy, sourced by a discrete torsion, in the dS vacua is investigated using Painleve geometries. It is argued that a D-instanton pair is created by a discrete torsion, with a Big Bang/Crunch, at the past horizon in a pure dS. Nucleation, of brane/anti-brane pair(s), is qualitatively analyzed to construct an effective space-time on a D 4-brane and its anti brane. Analysis re-assures the significant role played by a non-zero mode, of NS-NS two form, to generalize the notion of branes within a brane.
Nearly free electrons in a 5d delafossite oxide metal
Kushwaha, Pallavi; Sunko, Veronika; Moll, Philip J. W.; Bawden, Lewis; Riley, Jonathon M.; Nandi, Nabhanila; Rosner, Helge; Schmidt, Marcus P.; Arnold, Frank; Hassinger, Elena; Kim, Timur K.; Hoesch, Moritz; Mackenzie, Andrew P.; King, Phil D. C.
2015-01-01
Understanding the role of electron correlations in strong spin-orbit transition-metal oxides is key to the realization of numerous exotic phases including spin-orbit–assisted Mott insulators, correlated topological solids, and prospective new high-temperature superconductors. To date, most attention has been focused on the 5d iridium-based oxides. We instead consider the Pt-based delafossite oxide PtCoO2. Our transport measurements, performed on single-crystal samples etched to well-defined geometries using focused ion beam techniques, yield a room temperature resistivity of only 2.1 microhm·cm (μΩ-cm), establishing PtCoO2 as the most conductive oxide known. From angle-resolved photoemission and density functional theory, we show that the underlying Fermi surface is a single cylinder of nearly hexagonal cross-section, with very weak dispersion along kz. Despite being predominantly composed of d-orbital character, the conduction band is remarkably steep, with an average effective mass of only 1.14me. Moreover, the sharp spectral features observed in photoemission remain well defined with little additional broadening for more than 500 meV below EF, pointing to suppressed electron-electron scattering. Together, our findings establish PtCoO2 as a model nearly-free–electron system in a 5d delafossite transition-metal oxide. PMID:26601308
3.5 D temperature model of a coal stockpile
Ozdeniz, A.H.; Corumluoglu, O.; Kalayci, I.; Sensogut, C.
2008-07-01
Overproduced coal mines that are not sold should remain in coal stock sites. If these coal stockpiles remain at the stock yards over a certain period of time, a spontaneous combustion can be started. Coal stocks under combustion threat can cost too much economically to coal companies. Therefore, it is important to take some precautions for saving the stockpiles from the spontaneous combustion. In this research, a coal stock which was 5 m wide, 10 m long, and 3 m in height, with a weight of 120 tons, was monitored to observe internal temperature changes with respect to time under normal atmospheric conditions. Internal temperature measurements were obtained at 20 points distributed all over the two layers in the stockpile. Temperatures measured by a specially designed mechanism were then stored into a computer every 3 h for a period of 3 months. Afterward, this dataset was used to delineate 3.5 D temporal temperature distribution models for these two levels, and they were used to analyze and interpret what was seen in these models to derive some conclusions. It was openly seen, followed, and analyzed that internal temperature changes in the stockpile went up to 31{sup o}C by 3.5 D models created for this research.
Toward 5D image reconstruction for optical interferometry
NASA Astrophysics Data System (ADS)
Baron, Fabien; Kloppenborg, Brian; Monnier, John
2012-07-01
We report on our progress toward a flexible image reconstruction software for optical interferometry capable of "5D imaging" of stellar surfaces. 5D imaging is here defined as the capability to image directly one or several stars in three dimensions, with both the time and wavelength dependencies taken into account during the reconstruction process. Our algorithm makes use of the Healpix (Gorski et al., 2005) sphere partition scheme to tesselate the stellar surface, 3D Open Graphics Language (OpenGL) to model the spheroid geometry, and the Open Compute Language (OpenCL) framework for all other computations. We use the Monte Carlo Markov Chain software SQUEEZE to solve the image reconstruction problem on the surfaces of these stars. Finally, the Compressed Sensing and Bayesian Evidence paradigms are employed to determine the best regularization for spotted stars. Our algorithm makes use of the Healpix (reference needed) sphere partition scheme to tesselate the stellar surface, 3D Open Graphics Language (OpenGL) to model the spheroid, and the Open Compute Language (OpenCL) framework to model the Roche gravitational potential equation.
Equations on knot polynomials and 3d/5d duality
Mironov, A.; Morozov, A.
2012-09-24
We briefly review the current situation with various relations between knot/braid polynomials (Chern-Simons correlation functions), ordinary and extended, considered as functions of the representation and of the knot topology. These include linear skein relations, quadratic Plucker relations, as well as 'differential' and (quantum) A-polynomial structures. We pay a special attention to identity between the A-polynomial equations for knots and Baxter equations for quantum relativistic integrable systems, related through Seiberg-Witten theory to 5d super-Yang-Mills models and through the AGT relation to the q-Virasoro algebra. This identity is an important ingredient of emerging a 3d- 5d generalization of the AGT relation. The shape of the Baxter equation (including the values of coefficients) depend on the choice of the knot/braid. Thus, like the case of KP integrability, where (some, so far torus) knots parameterize particular points of the Universal Grassmannian, in this relation they parameterize particular points in the moduli space of many-body integrable systems of relativistic type.
Fermionic Schwinger effect and induced current in de Sitter space
NASA Astrophysics Data System (ADS)
Hayashinaka, Takahiro; Fujita, Tomohiro; Yokoyama, Jun'ichi
2016-07-01
We explore Schwinger effect of spin 1/2 charged particles with static electric field in 1+3 dimensional de Sitter spacetime. We analytically calculate the vacuum expectation value of the spinor current which is induced by the produced particles in the electric field. The renormalization is performed with the adiabatic subtraction scheme. We find that the current becomes negative, namely it flows in the direction opposite to the electric field, if the electric field is weaker than a certain threshold value depending on the fermion mass, which is also known to happen in the case of scalar charged particles in 1+3 de Sitter spacetime. Contrary to the scalar case, however, the IR hyperconductivity is absent in the spinor case.
Schwinger effect and backreaction in de Sitter spacetime
NASA Astrophysics Data System (ADS)
Stahl, Clément; Xue, She-Sheng
2016-09-01
We consider the particle-antiparticle pairs produced by both a strong electric field and de Sitter curvature. We investigate in 1 + 1 D the backreaction of the pairs on the electromagnetic field. To do so we describe the canonical quantization of an electromagnetic field in de Sitter space and add in the Einstein-Maxwell equation the fermionic current induced by the pairs. After solving this equation, we find that the electric field gets either damped or unaffected depending on the value of the pair mass and the gauge coupling. No enhancement of the electromagnetic field to support a magnetogenesis scenario is found. The physical picture is that the Schwinger pairs locally created screen the production and amplification of the electromagnetic field. However, if one considers light bosons created by the Schwinger mechanism, we report a solution to the Einstein-Maxwell equation with an enhancement of the electromagnetic field. This solution could be a new path to primordial magnetogenesis.
Gravitomagnetic effects in Kerr-de Sitter space-time
Iorio, Lorenzo; Ruggiero, Matteo Luca E-mail: matteo.ruggiero@polito.it
2009-03-15
We explicitly worked out the orbital effects induced on the trajectory of a test particle by the the weak-field approximation of the Kerr-de Sitter metric. It results that the node, the pericentre and the mean anomaly undergo secular precessions proportional to k. We used such theoretical predictions and the latest observational determinations of the non-standard precessions of the perihelia of the inner planets of the Solar System to put a bound on k getting k {<=} 10{sup -29} m{sup -2}. The node rate of the LAGEOS Earth's satellite yields k {<=} 10{sup -26} m{sup -2}. The periastron precession of the double pulsar PSR J0737-3039A/B allows to obtain k {<=} 3 Multiplication-Sign 10{sup -21} m{sup -2}. Interpreting k as a cosmological constant {Lambda}, it turns out that such constraints are weaker than those obtained from the Schwarzschild-de Sitter metric.
Quantum nonthermal radiation of nonstationary rotating de Sitter cosmological model
NASA Astrophysics Data System (ADS)
Meitei, Irom Ablu; Singh, T. Ibungochouba; Singh, K. Yugindro
2014-08-01
Using the Hamilton-Jacobi method a study of quantum nonthermal radiation of nonstationary rotating de Sitter cosmological model is carried out. It is shown that there exist seas of positive and negative energy states in the vicinity of the cosmological event horizon and there also exists a forbidden energy gap between the two seas. The forbidden energy gap vanishes on the surface of the cosmological event horizon so that the positive and negative energy levels overlap. The width of the forbidden energy gap and the energy of the particle at the cosmological event horizon are found to depend on the cosmological constant, the rotation parameter, positions of the particle and the cosmological event horizon, angular momentum of the particle, evaporation rate and shape of the cosmological event horizon. The tunneling probability of the emitted particles constituting Hawking radiation is also deduced for stationary nonrotating de Sitter cosmological model and the standard Hawking temperature is recovered.
de Sitter Vacua from an Anomalous Gauge Symmetry
NASA Astrophysics Data System (ADS)
Buchmuller, Wilfried; Dierigl, Markus; Ruehle, Fabian; Schweizer, Julian
2016-06-01
We find a new class of metastable de Sitter solutions in compactifications of six-dimensional supergravity motivated by type IIB or heterotic string vacua. Two Fayet-Iliopoulos terms of a local U(1) symmetry are generated by magnetic flux and by the Green-Schwarz term canceling the gauge anomalies, respectively. The interplay between the induced D term, the moduli dependence of the effective gauge coupling, and a nonperturbative superpotential stabilizes the moduli and determines the size of the extra dimensions.
Semiclassical fermion pair creation in de Sitter spacetime
Stahl, Clément Eckhard, Strobel
2015-12-17
We present a method to semiclassically compute the pair creation rate of bosons and fermions in de Sitter spacetime. The results in the bosonic case agree with the ones in the literature. We find that for the constant electric field the fermionic and bosonic pair creation rate are the same. This analogy of bosons and fermions in the semiclassical limit is known from several flat spacetime examples.
Hawking radiation of the Vaidya Bonner de Sitter black hole
NASA Astrophysics Data System (ADS)
Chen, Deyou; Yang, Shuzheng
2007-08-01
Considering the unfixed background space-time and the self-gravitational interaction, we view the Hawking radiation of the Vaidya Bonner de Sitter black hole by the Hamilton Jacobi method and the radial geodesic method. The result shows the tunneling rate is related not only to the change of Bekenstein Hawking entropy but also to the integral of the black hole mass and charge, which does not satisfy the unitary theory and is not in accordance with the known result.
The solar photon thruster as a terrestrial pole sitter.
Matloff, Gregory L
2004-05-01
Geosynchronous satellites are invisible at high latitudes. A pole-sitting spacecraft would have communication, climate-studies, and near-polar Earth observation applications. We present a pole-sitter based on the solar photon thruster (SPT), a two-sail variant of the solar sail using a large curved collector sail (always normal to the Sun) to direct sunlight against a much smaller thruster. Thrust decreases slower for an SPT than for a conventional sail arrangement as the angle between sunlight and the collector normal increases. An SPT pole-sitter is offset from the terrestrial pole so that a component of Earth gravity balances the solar radiation-pressure component pushing the SPT off station. The component of gravitational attraction of the Earth pulling the spacecraft towards Earth is also balanced by a solar radiation-pressure component. Results are presented for 80-100% collector/thruster reflectivities. For a spacecraft areal mass thickness of 0.002 kg/m(2), collector and thruster reflectivities of 0.9, the SPT can be situated above latitude 45 degrees at a distance of approximately 60 Earth radii. An SPT pole sitter would be affected by lunar perturbation, which can be compensated for by an on-board rocket thruster producing 2 x 10(-6) g acceleration, a second SPT thruster sail thrusting against the influence of the Moon, or by directing a microwave beam against the spacecraft. Since an SPT pole sitter is in a position rather than an orbit, the effect of terrestrial gravitation limits the size and design of the payload package, which limits terrestrial target resolution. PMID:15220163
Dynamics of test bodies with spin in de Sitter spacetime
Obukhov, Yuri N.; Puetzfeld, Dirk
2011-02-15
We study the motion of spinning test bodies in the de Sitter spacetime of constant positive curvature. With the help of the 10 Killing vectors, we derive the 4-momentum and the tensor of spin explicitly in terms of the spacetime coordinates. However, in order to find the actual trajectories, one needs to impose the so-called supplementary condition. We discuss the dynamics of spinning test bodies for the cases of the Frenkel and Tulczyjew conditions.
Solutions of minimal four-dimensional de Sitter supergravity
NASA Astrophysics Data System (ADS)
Gutowski, J. B.; Sabra, W. A.
2010-12-01
Pseudo-supersymmetric solutions of minimal N = 2, D = 4 de Sitter supergravity are classified using spinorial geometry techniques. We find three classes of solutions. The first class of solution consists of geometries which are fibrations over a three-dimensional manifold equipped with a Gauduchon-Tod structure. The second class of solution is the cosmological Majumdar-Papapetrou solution of Kastor and Traschen, and the third corresponds to gravitational waves propagating in the Nariai cosmology.
Incompressible fluids of the de Sitter horizon and beyond
NASA Astrophysics Data System (ADS)
Anninos, Dionysios; Anous, Tarek; Bredberg, Irene; Ng, Gim Seng
2012-05-01
There are (at least) two surfaces of particular interest in eternal de Sitter space. One is the timelike hypersurface constituting the lab wall of a static patch observer and the other is the future boundary of global de Sitter space. We study both linear and non-linear deformations of four-dimensional de Sitter space which obey the Einstein equation. Our deformations leave the induced conformal metric and trace of the extrinsic curvature unchanged for a fixed hypersurface. This hypersurface is either timelike within the static patch or spacelike in the future diamond. We require the deformations to be regular at the future horizon of the static patch observer. For linearized perturbations in the future diamond, this corresponds to imposing incoming flux solely from the future horizon of a single static patch observer. When the slices are arbitrarily close to the cosmological horizon, the finite deformations are characterized by solutions to the incompressible Navier- Stokes equation for both spacelike and timelike hypersurfaces. We then study, at the level of linearized gravity, the change in the discrete dispersion relation as we push the timelike hypersurface toward the worldline of the static patch. Finally, we study the spectrum of linearized solutions as the spacelike slices are pushed to future infinity and relate our calculations to analogous ones in the context of massless topological black holes in AdS4.
Probing Planckian physics in de Sitter space with quantum correlations
Feng, Jun; Zhang, Yao-Zhong; Gould, Mark D.; Fan, Heng; Sun, Cheng-Yi; Yang, Wen-Li
2014-12-15
We study the quantum correlation and quantum communication channel of both free scalar and fermionic fields in de Sitter space, while the Planckian modification presented by the choice of a particular α-vacuum has been considered. We show the occurrence of degradation of quantum entanglement between field modes for an inertial observer in curved space, due to the radiation associated with its cosmological horizon. Comparing with standard Bunch–Davies choice, the possible Planckian physics causes some extra decrement on the quantum correlation, which may provide the means to detect quantum gravitational effects via quantum information methodology in future. Beyond single-mode approximation, we construct proper Unruh modes admitting general α-vacua, and find a convergent feature of both bosonic and fermionic entanglements. In particular, we show that the convergent points of fermionic entanglement negativity are dependent on the choice of α. Moreover, an one-to-one correspondence between convergent points H{sub c} of negativity and zeros of quantum capacity of quantum channels in de Sitter space has been proved. - Highlights: • Quantum correlation and quantum channel in de Sitter space are studied. • Gibbons–Hawking effect causes entanglement degradation for static observer. • Planckian physics causes extra decrement on quantum correlation. • Convergent feature of negativity relies on the choice of alpha-vacua. • Link between negativity convergence and quantum channel capacity is given.
Reconstruction of 5d Cosmological Models from Recent Observations
NASA Astrophysics Data System (ADS)
Zhang, Chengwu; Xu, Lixin; Ping, Yongli; Liu, Hongya
We use a parameterized equation of state (EOS) of dark energy to a 5D Ricci-flat cosmological solution and suppose the universe contains two major components: dark matter and dark energy. Using the recent observational datasets: the latest 182 type Ia Supernovae Gold data, the three-year WMAP CMB shift parameter and the SDSS baryon acoustic peak, we obtain the best fit values of the EOS and two major components' evolution. We find that the best fit EOS crosses -1 in the near past where z ≃ 0.07, the present best fit value of wx(0) < -1 and for this model, the universe experiences the acceleration at about z ≃ 0.5.
Gauge and modulus inflation from 5D orbifold SUGRA
NASA Astrophysics Data System (ADS)
Paccetti Correia, Filipe; Schmidt, Michael G.; Tavartkiladze, Zurab
2006-04-01
We study the inflationary scenarios driven by a Wilson line field—the fifth component of a 5D gauge field and corresponding modulus field—within S/Z orbifold supergravity (SUGRA). We use our off shell superfield formulation and give a detailed description of the issue of SUSY breaking by the F-component of the radion superfield. By a suitably gauged U1 symmetry and including couplings with compensator supermultiplets and a linear multiplet, we achieve a self consistent radion mediated SUSY breaking of no scale type. The inflaton 1-loop effective potential has attractive features needed for successful inflation. An interesting feature of both presented inflationary scenarios are the red tilted spectra with n≃0.96. For gauge inflation we obtain a significant tensor to scalar ratio (r≈0.1) of the density perturbations, while for the modulus inflation r is strongly suppressed.
5D extremal rotating black holes and CFT duals
NASA Astrophysics Data System (ADS)
Loran, Farhang; Soltanpanahi, Hesam
2009-08-01
Kerr/CFT correspondence has been recently applied to various types of 5D extremal rotating black holes. A common feature of all such examples is the existence of two chiral CFT duals corresponding to the U(1) symmetries of the near horizon geometry. In this paper, by studying the moduli space of the near horizon metric of five-dimensional extremal black holes which are asymptotically flat or AdS, we realize an SL(2, {\\mathbb Z} ) modular group which is a symmetry of the near horizon geometry. We show that there is a lattice of chiral CFT duals corresponding to the moduli points identified under the action of the modular group. The microscopic entropy corresponding to all such CFTs is equivalent and is in agreement with the Bekenstein-Hawking entropy.
5D gravitational waves from complexified black rings
NASA Astrophysics Data System (ADS)
Bretón, N.; Feinstein, A.; López, L. A.
2010-02-01
In this paper we construct and briefly study the 5D time-dependent solutions of general relativity obtained via double analytic continuation of the black hole (Myers-Perry) and of the black ring solutions with a double (Pomeransky-Senkov) and a single rotation (Emparan-Reall). The new solutions take the form of a generalized Einstein-Rosen cosmology representing gravitational waves propagating in a closed universe. In this context the rotation parameters of the rings can be interpreted as the extra wave polarizations, while it is interesting to state that the waves obtained from Myers-Perry Black holes exhibit an extra boost-rotational symmetry in higher dimensions which signals their better behavior at null infinity. The analogue to the C-energy is analyzed.
Black hole solutions in 5D Horava-Lifshitz gravity
Koutsoumbas, George; Papantonopoulos, Eletherios; Pasipoularides, Pavlos; Tsoukalas, Minas
2010-06-15
We study the full spectrum of spherically symmetric solutions in the five-dimensional nonprojectable Horava-Lifshitz type gravity theories. For appropriate ranges of the coupling parameters, we have found several classes of solutions which are characterized by an AdS{sub 5}, dS{sub 5}, or flat large distance asymptotic behavior, plus the standard 1/r{sup 2} tail of the usual five-dimensional Schwarzschild black holes. In addition we have found solutions with an unconventional short or large distance behavior, and, for a special range of the coupling parameters, solutions which coincide with black hole solutions of conventional relativistic five-dimensional Gauss-Bonnet gravity.
Jelsma, Jennifer
2010-06-01
The aim of this study was to investigate the performance of the recent EQ-5D-Y instrument compared with the standard EQ-5D in assessing the health-related quality of life of high school children in Cape Town. Either the EQ-5D or the EQ-5D-Y was given to high school children. The sample consisted of 521 respondents. The EQ-5D-Y was found to be superior in that there were statistically significant fewer missed item responses, both in the domains and the health status Visual Analogue Scale (VAS). A grade differential was noted with more missing responses in the lower grades, particularly with the EQ-5D. More children reported problems with the mobility, self-care and anxiety and depression domains when responding to the EQ-5D-Y. In addition, the mean VAS score was marginally greater using the EQ-5D-Y. The EQ-5D-Y performed better than the EQ-5D, particularly in the younger children, and should be used in early secondary school. The EQ-5D-Y generated a wider range of responses in both the domains and the VAS, and may be more responsive than the Adult version. The two seem to give different results and consequently should be considered two related but separate instruments. PMID:20351650
Closed conformal Killing Yano tensor and the uniqueness of generalized Kerr NUT de Sitter spacetime
NASA Astrophysics Data System (ADS)
Houri, Tsuyoshi; Oota, Takeshi; Yasui, Yukinori
2009-02-01
The higher-dimensional Kerr NUT de Sitter spacetime describes the general rotating asymptotically de Sitter black hole with NUT parameters. It is known that such a spacetime possesses a rank-2 closed conformal Killing Yano (CKY) tensor as a 'hidden' symmetry which provides the separation of variables for the geodesic equations and Klein Gordon equations. We present a classification of higher-dimensional spacetimes admitting a rank-2 closed CKY tensor. This provides a generalization of the Kerr NUT de Sitter spacetime. In particular, we show that the Kerr NUT de Sitter spacetime is the only spacetime with a non-degenerate CKY tensor.
Coulomb's law corrections and fermion field localization in a tachyonic de Sitter thick braneworld
NASA Astrophysics Data System (ADS)
Cartas-Fuentevilla, Roberto; Escalante, Alberto; Germán, Gabriel; Herrera-Aguilar, Alfredo; Rigel Mora-Luna, Refugio
2016-05-01
Following recent studies which show that it is possible to localize gravity as well as scalar and gauge vector fields in a tachyonic de Sitter thick braneworld, we investigate the solution of the gauge hierarchy problem, the localization of fermion fields in this model, the recovering of the Coulomb law on the non-relativistic limit of the Yukawa interaction between bulk fermions and gauge bosons localized in the brane, and confront the predicted 5D corrections to the photon mass with its upper experimental/observational bounds, finding the model physically viable since it passes these tests. In order to achieve the latter aims we first consider the Yukawa interaction term between the fermionic and the tachyonic scalar fields MF(T)ΨΨ̅ in the action and analyze four distinct tachyonic functions F(T) that lead to four different structures of the respective fermionic mass spectra with different physics. In particular, localization of the massless left-chiral fermion zero mode is possible for three of these cases. We further analyze the phenomenology of these Yukawa interactions among fermion fields and gauge bosons localized on the brane and obtain the crucial and necessary information to compute the corrections to Coulomb's law coming from massive KK vector modes in the non-relativistic limit. These corrections are exponentially suppressed due to the presence of the mass gap in the mass spectrum of the bulk gauge vector field. From our results we conclude that corrections to Coulomb's law in the thin brane limit have the same form (up to a numerical factor) as far as the left-chiral massless fermion field is localized on the brane. Finally we compute the corrections to the Coulomb's law for an arbitrarily thick brane scenario which can be interpreted as 5D corrections to the photon mass. By performing consistent estimations with brane phenomenology, we found that the predicted corrections to the photon mass, which are well bounded by the experimentally observed or
Inferring segmented dense motion layers using 5D tensor voting.
Min, Changki; Medioni, Gérard
2008-09-01
We present a novel local spatiotemporal approach to produce motion segmentation and dense temporal trajectories from an image sequence. A common representation of image sequences is a 3D spatiotemporal volume, (x,y,t), and its corresponding mathematical formalism is the fiber bundle. However, directly enforcing the spatiotemporal smoothness constraint is difficult in the fiber bundle representation. Thus, we convert the representation into a new 5D space (x,y,t,vx,vy) with an additional velocity domain, where each moving object produces a separate 3D smooth layer. The smoothness constraint is now enforced by extracting 3D layers using the tensor voting framework in a single step that solves both correspondence and segmentation simultaneously. Motion segmentation is achieved by identifying those layers, and the dense temporal trajectories are obtained by converting the layers back into the fiber bundle representation. We proceed to address three applications (tracking, mosaic, and 3D reconstruction) that are hard to solve from the video stream directly because of the segmentation and dense matching steps, but become straightforward with our framework. The approach does not make restrictive assumptions about the observed scene or camera motion and is therefore generally applicable. We present results on a number of data sets. PMID:18617717
Kinematics of particles with quantum-de Sitter-inspired symmetries
NASA Astrophysics Data System (ADS)
Barcaroli, Leonardo; Gubitosi, Giulia
2016-06-01
We present the first detailed study of the kinematics of free relativistic particles whose symmetries are compatible with the ones described by a quantum deformation of the de Sitter algebra, known as q -de Sitter Hopf algebra. In such algebra, the quantum deformation parameter is a function of the Planck length ℓ and the de Sitter radius H-1, such that when the Planck length vanishes, the algebra reduces to the de Sitter algebra, while when the de Sitter radius is sent to infinity, one recovers the κ -Poincaré Hopf algebra. In the first limit, the picture is that of a particle with trivial momentum space geometry moving on de Sitter spacetime; in the second one, the picture is that of a particle with de Sitter momentum space geometry moving on Minkowski spacetime. When both the Planck length and the inverse of the de Sitter radius are nonzero, effects due to spacetime curvature and nontrivial momentum space geometry are both present and affect each other. The particles' motion is then described in a full phase-space picture. We find that redshift effects that are usually associated with spacetime curvature become energy dependent. Also, the energy dependence of the particles' travel times that is usually associated with momentum space nontrivial properties is modified in a curvature-dependent way.
Gauge theory of a group of diffeomorphisms. II. The conformal and de Sitter groups
NASA Astrophysics Data System (ADS)
Lord, Eric A.
1986-12-01
The extension of Hehl's Poincaré gauge theory to more general groups that include space-time diffeomorphisms is worked out for two particular examples, one corresponding to the action of the conformal group on Minkowski space, and the other to the action of the de Sitter group on de Sitter space, and the effect of these groups on physical fields.
How To Feel Good about Leaving Your Children with A Sitter.
ERIC Educational Resources Information Center
Lane, Jordan
2003-01-01
Presents suggestions to help parents feel at ease when they leave their children with a babysitter, offering tips on: how to find a sitter, scheduling the sitter, paying fairly, laying down the rules, ensuring safety, preparing a list, and providing food. (SM)
CYB5D2 displays tumor suppression activities towards cervical cancer.
Xie, Yanyun; Shen, Yen Ting; Kapoor, Anil; Ojo, Diane; Wei, Fengxiang; De Melo, Jason; Lin, Xiaozeng; Wong, Nicholas; Yan, Judy; Tao, Lijian; Major, Pierre; Tang, Damu
2016-04-01
Cervical cancer is caused by infections with human papillomaviruses (HPV) and genetic alternations in the cervical epithelium. While the former is well studied, the latter remains unclear. We report here that CYB5D2/Neuferricin possesses tumor suppressing activity towards cervical tumorigenesis. Ectopic expression of CYB5D2 did not affect HeLa cell proliferation and the cell's ability to form xenograft tumors, but significantly inhibited HeLa cell invasion in vitro and the cell-produced lung metastasis in NOD/SCID mice. Knockdown of CYB5D2 enhanced HeLa cell invasion. Two mutations in CYB5D2, the substitutions of arginine (R) 7 with either proline (P) or glycine (G), were reported in colon cancer. Both CYB5D2(R7P) and CYB5D2(R7G) were incapable of inhibiting HeLa cell invasion. CYB5D2 binds heme, in which aspartate (D) 86 is required. While CYB5D2(D86G) is heme-binding defective, it inhibited HeLa cell invasion. On the other hand, CYB5D2(R7P) and CYB5D2(R7G) bound heme but did not inhibit HeLa cell invasion. Collectively, CYB5D2 inhibits HeLa cell invasion independently of its heme binding. Furthermore, immunohistochemistry examination of CYB5D2 expression in 20 normal cervical tissues and 40 cervical squamous cell carcinomas (SCC) revealed a CYB5D2 reduction in 87.5% (35/40) of SCC. Analysis of CYB5D2 gene expression and genomic alteration data available from Oncomeine™ detected significant reductions of CYB5D2 mRNA in 40 SCCs and CYB5D2 gene copy number in 107 SCCs. Collectively, we provide evidence that CYB5D2 is a candidate tumor suppressor of cervical tumorigenesis. PMID:26692170
Inflation in de Sitter spacetime and CMB large scale anomaly
NASA Astrophysics Data System (ADS)
Zhao, Dong; Li, Ming-Hua; Wang, Ping; Chang, Zhe
2015-09-01
The influence of cosmological constant-type dark energy in the early universe is investigated. This is accommodated by a new dispersion relation in de Sitter spacetime. We perform a global fit to explore the cosmological parameter space by using the CosmoMC package with the recently released Planck TT and WMAP polarization datasets. Using the results from the global fit, we compute a new CMB temperature-temperature (TT) spectrum. The obtained TT spectrum has lower power compared with that based on the ACDM model at large scales. Supported by National Natural Science Foundation of China (11375203)
Reexamination of the Power Spectrum in De Sitter Inflation
NASA Astrophysics Data System (ADS)
Agulló, Iván; Navarro-Salas, José; Olmo, Gonzalo J.; Parker, Leonard
2008-10-01
We find that the amplitude of quantum fluctuations of the invariant de Sitter vacuum coincides exactly with that of the vacuum of a comoving observer for a massless scalar (inflaton) field. We propose redefining the actual physical power spectrum as the difference between the amplitudes of the above vacua. An inertial particle detector continues to observe the Gibbons-Hawking temperature. However, although the resulting power spectrum is still scale-free, its amplitude can be drastically reduced since now, instead of the Hubble’s scale at the inflationary period, it is determined by the square of the mass of the inflaton fluctuation field.
Holographic de Sitter Geometry from Entanglement in Conformal Field Theory
NASA Astrophysics Data System (ADS)
de Boer, Jan; Heller, Michal P.; Myers, Robert C.; Neiman, Yasha
2016-02-01
We demonstrate that, for general conformal field theories (CFTs), the entanglement for small perturbations of the vacuum is organized in a novel holographic way. For spherical entangling regions in a constant time slice, perturbations in the entanglement entropy are solutions of a Klein-Gordon equation in an auxiliary de Sitter (dS) spacetime. The role of the emergent timelike direction in dS spacetime is played by the size of the entangling sphere. For CFTs with extra conserved charges, e.g., higher-spin charges, we show that each charge gives rise to a separate dynamical scalar field in dS spacetime.
Schwarzschild-De Sitter Black Hole from Entropic Viewpoint
NASA Astrophysics Data System (ADS)
Ee, Chang-Young; Eune, Myungseok; Kimm, Kyoungtae; Lee, Daeho
In a Schwarzschild-de Sitter space, we consider an equipotential surface which consists of two holographic screens. Adapting the Bousso-Hawking's reference point of vanishing force, we divide the space into two regions, which are from the reference point to each holographic screen. These two regions can be treated as independent thermodynamical systems, because the Bousso-Hawking reference point with zero temperature behaves like a thermally insulating wall. The entropy obtained in this way agrees with the conventional results: (i) when the holographic screens lie at the black hole and cosmological horizons, (ii) in the Nariai limit.
The deflationary universe: An instability of the de Sitter universe
NASA Astrophysics Data System (ADS)
Barrow, John D.
1986-11-01
The relevance is discussed of the initial value structure of the cosmological problem for inflationary explanations of its present structure. Existing proofs of the cosmic ``no hair'' conjecture are found to make use of an unrealistic strong energy condition on the stress tensor of the matter fields not driving the inflation. It is shown by explicit example that the no hair conjecture fails even in isotropic cosmological models if the strong energy conditions is relaxed. A class of exact cosmological models are given which begin in a de Sitter state but subsequently deflate towards the flat Friedman model. Various implications of these examples are discussed.
An Infinite Number of Static Soliton Solutions to the 5D Einstein-Maxwell Equations
NASA Astrophysics Data System (ADS)
Azuma, T.; Koikawa, T.
2007-08-01
The soliton technique is applied to the 5D static Einstein-Maxwell equations, and an infinite number of solutions are explicitly obtained. We study the rod structure of 2-soliton solutions and show that the 5D Reissner-Nordström solution and the 5D Majumdar-Papapetrou-type solution are included among the 2-soliton solutions.
Initial states and infrared physics in locally de Sitter spacetime
NASA Astrophysics Data System (ADS)
Larjo, Klaus; Lowe, David A.
2012-02-01
The long wavelength physics in a de Sitter region depends on the initial quantum state. While such long wavelength physics is under control for massive fields near the Hartle-Hawking vacuum state, such initial states make unnatural assumptions about initial data outside the region of causal contact of a local observer. We argue that a reasonable approximation to a maximum entropy state, one that makes minimal assumptions outside an observer’s horizon volume, is one where a cutoff is placed on a surface bounded by timelike geodesics, just outside the horizon. For sufficiently early times, such a cutoff induces secular logarithmic divergences with the expansion of the region. For massive fields, these effects sum to finite corrections at sufficiently late times. The difference between the cutoff correlators and Hartle-Hawking correlators provides a measure of the theoretical uncertainty due to lack of knowledge of the initial state in causally disconnected regions. These differences are negligible for primordial inflation, but can become significant during epochs with very long-lived de Sitter regions, such as we may be entering now.
Auxiliary ``Massless'' Spin-2 Field in De Sitter Universe
NASA Astrophysics Data System (ADS)
Pejhan, H.; Tanhayi, M. R.; Takook, M. V.
2010-09-01
For the tensor field of rank-2 there are two unitary irreducible representation (UIR) in de Sitter (dS) space denoted by Pi^{±}_{2,2} and Pi^{±}_{2,1} (Dixmier in Bull Soc. Math. France 89:9, 1961). In the flat limit only the Pi^{±}_{2,2} coincides to the UIR of Poincaré group, the second one becomes important in the study of conformal gravity. In the previous work, Dirac’s six-cone formalism has been utilized to obtain conformally invariant (CI) field equation for the “massless” spin-2 field in dS space (Dehghani et al. in Phys. Rev. D 77:064028, 2008). This equation results in a field which transformed according to Pi^{±}_{2,1}, we name this field the auxiliary field. In this paper this auxiliary field is considered and also related two-point function is calculated as a product of a polarization tensor and “massless” conformally coupled scalar field. This two-point function is de Sitter invariant.
Rotating, radiating mass imbedded in a de Sitter universe
Hadley, R.H.
1991-01-01
This study presents a new solution to the Einstein field equations for a rotating, radiating mass imbedded in a de Sitter universe, the Kerr de Sitter-Vaidya or KDV line element. Solutions presented were precursers to the new solution. One of these, the Vaidya-Mallett or VM metric is used as a starting point to derive the KDV metric by a method called complexification. The mathematical framework for the KDV metric is the Newman-Penrose formalism, a powerful tool that provides insight into the various properties of the space-time geometry and optical properties of the radiation field. Using this formalism, the metric can be expressed in tetrad form and the Newman-Penrose spin coefficient equations solved for tetrad components of the trace-free Ricci tensor, Ricci scalar, Maxwell tensor, and Weyl tensor. Using the tetrad components of the Weyl tensor, the Petrov type for the gravitational and electromagnetic fields are found. The new solution is shown to be a solution to the Einstein-Maxwell equations for a particular choice of energy-momentum tensor which is studied in detail.
Superluminal Neutrinos from Special Relativity with de Sitter Spacetime Symmetry
NASA Astrophysics Data System (ADS)
Yan, Mu-Lin; Xiao, Neng-Chao; Huang, Wei; Hu, Sen
2012-05-01
We explore the recent OPERA experiment of superluminal neutrinos in the framework of special relativity with de Sitter spacetime symmetry (dS-SR). According to Einstein, a photon is treated as a massless particle in the framework of special relativity. In special relativity (SR) we have the universal parameter c, the photon velocity cphoton and the phase velocity of a light wave in vacuum cwave = λν. Due to the null experiments of Michelson-Morley we have c = cwave. The parameter cphoton is determined by the Noether charges corresponding to the spacetime symmetries of SR. In Einstein's special relativity (E-SR) we have c = cphoton. In dS-SR, i.e. the special relativity with SO(4, 1) de Sitter spacetime symmetry, we have cphoton > c. In this paper, the OPERA datum are examined in the framework of dS-SR. We show that OPERA anomaly is in agreement with the prediction of dS-SR with R≃1.95×1012 l.y. Based on the p-E relation of dS-SR, we also prove that the Cohen and Glashow's argument of possible superluminal neutrino's Cherenkov-like radiation is forbidden. We conclude that OPERA and ICARUS results are consistent and they are explained in the dS-SR framework.
Probing Planckian physics in de Sitter space with quantum correlations
NASA Astrophysics Data System (ADS)
Feng, Jun; Zhang, Yao-Zhong; Gould, Mark D.; Fan, Heng; Sun, Cheng-Yi; Yang, Wen-Li
2014-12-01
We study the quantum correlation and quantum communication channel of both free scalar and fermionic fields in de Sitter space, while the Planckian modification presented by the choice of a particular α-vacuum has been considered. We show the occurrence of degradation of quantum entanglement between field modes for an inertial observer in curved space, due to the radiation associated with its cosmological horizon. Comparing with standard Bunch-Davies choice, the possible Planckian physics causes some extra decrement on the quantum correlation, which may provide the means to detect quantum gravitational effects via quantum information methodology in future. Beyond single-mode approximation, we construct proper Unruh modes admitting general α-vacua, and find a convergent feature of both bosonic and fermionic entanglements. In particular, we show that the convergent points of fermionic entanglement negativity are dependent on the choice of α. Moreover, an one-to-one correspondence between convergent points Hc of negativity and zeros of quantum capacity of quantum channels in de Sitter space has been proved.
One-loop gravitational wave spectrum in de Sitter spacetime
Fröb, Markus B.; Verdaguer, Enric
2012-08-01
The two-point function for tensor metric perturbations around de Sitter spacetime including one-loop corrections from massless conformally coupled scalar fields is calculated exactly. We work in the Poincare patch (with spatially flat sections) and employ dimensional regularization for the renormalization process. Unlike previous studies we obtain the result for arbitrary time separations rather than just equal times. Moreover, in contrast to existing results for tensor perturbations, ours is manifestly invariant with respect to the subgroup of de Sitter isometries corresponding to a simultaneous time translation and rescaling of the spatial coordinates. Having selected the right initial state for the interacting theory via an appropriate iε prescription is crucial for that. Finally, we show that although the two-point function is a well-defined spacetime distribution, the equal-time limit of its spatial Fourier transform is divergent. Therefore, contrary to the well-defined distribution for arbitrary time separations, the power spectrum is strictly speaking ill-defined when loop corrections are included.
Quasinormal modes in de Sitter space: Plane wave method
NASA Astrophysics Data System (ADS)
Tanhayi, M. Reza
2014-09-01
Recently, in the context of dS/CFT correspondence, quasinormal modes have been put forward to address certain features of this conjecture. In particular, it is argued that the dual states of quasinormal modes are in fact the states of CFT3 which are created by operator insertions. For a scalar field in dS4, quasinormal modes which are singular on the past horizon of the south pole and decay exponentially towards the future have been considered in [G. S. Ng and A. Strominger, Classical Quantum Gravity 30, 104002 (2013); D. L. Jafferis et al., arXiv:1305.5523]; these modes lie in two complex highest-weight representations of the dS4 isometry group. In this work, we present a simple group representation analysis of these modes so that the de Sitter invariance is obviously manifest. By making use of the so-called plane wave method, we will show that the quasinormal modes correspond to one class of the unitary irreducible representation of the de Sitter group. This consideration could be generalized straightforwardly for higher-spin fields and higher dimensions; in particular, we will study the quasinormal modes for gauge and spinor fields, and, in the case of a scalar field, the generalization to higher dimensions is also obtained.
A note on entropy of de Sitter black holes
NASA Astrophysics Data System (ADS)
Bhattacharya, Sourav
2016-03-01
A de Sitter black hole or a black hole spacetime endowed with a positive cosmological constant has two Killing horizons—a black hole and a cosmological event horizon surrounding it. It is natural to expect that the total Bekenstein-Hawking entropy of such spacetimes should be the sum of the two horizons' areas. In this work we apply the recently developed formalism using the Gibbons-Hawking-York boundary term and the near horizon symmetries to derive the total entropy of such two horizon spacetimes. We construct a suitable general geometric set up for general stationary axisymmetric spacetimes with two or more than two commuting Killing vector fields in an arbitrary spacetime dimensions. This framework helps us to deal with both horizons on an equal footing. We show that in order to obtain the total entropy of such spacetimes, the near horizon mode functions for the diffeomorphism generating vector fields have to be restricted in a certain manner, compared to the single horizon spacetimes. We next discuss specific known exact solutions belonging to the Kerr-Newman or the Plebanski-Demianski-de Sitter families to show that they fall into the category of our general framework. We end with a sketch of further possible extensions of this work.
NASA Astrophysics Data System (ADS)
Maneva, Y. G.; Poedts, S.; Araneda, J. A.
2016-02-01
We compare the results from 1.5D and 2.5D hybrid simulations (with fluid electrons, and kinetic/particle-in-cell protons and α particles) to investigate the effect of the solar wind expansion on the evolution of ion relative drifts in collisionless fast wind streams. We initialize the system with initial relative drifts and follow its evolution in time within and without the expanding box model, which takes into account the gradual solar wind expansion in the interplanetary medium. The decay of the differential streaming follows similar pattern in the 1.5D and 2.5D non-expanding cases. For the 1.5D studies we find no difference in the evolution of the initial relative drift speed with and without expansion, whereas in the two-dimensional case the differential streaming is further suppressed once the solar wind expansion is taken into account. This implies that a stronger acceleration source is required to compensate for the effect of the expansion and produce the observed solar wind acceleration rate. The 1.5D case shows stronger oscillations in all plasma properties with higher temperature anisotropies for the minor ions in the first few hundred gyro-periods of the simulations. Yet the preferential perpendicular heating for the minor ions is stronger in the 2.5D case with higher temperature anisotropies at the final stage.
NASA Astrophysics Data System (ADS)
Suresh Kumar, J.; Pavani, K.; Sasikala, T.; Jayasimhadri, M.; Jang, Kiwan; Rama Moorthy, L.
2011-02-01
Calcium fluoroborate (CFB) glasses doped with different concentrations of Tb3+ ions have been prepared with molar composition of (42-x) B2O3 + 20 CaF2 +15 CaO + 15 BaO + 8 Al2O3 + x TbF3 (x=0.05, 0.1, 0.5, 1.0, 2.0 and 4.0) by melt quenching method. Optical absorption spectrum for 1.0 mol% of Tb3+:CFB glass was recorded in UV-Vis-NIR regions. Radiative parameters such as radiative transition probabilities (AR), radiative lifetimes (τR), radiative branching ratios (βR) for the 5D3 and 5D4 excited states have been calculated by using the Judd-Ofelt parameters (Ωλ=2,4,6). The luminescence spectra recorded for different concentrations of Tb3+ ions in CFB glasses exhibit seven and four bands originating from 5D4 and 5D3 excited states respectively. As the concentration of Tb3+ ions increases the intensities of luminescence peaks originating from 5D4 state increases, whereas, the quenching of intensities has been observed for the emission peaks originating from 5D3 state due to energy transfer through cross-relaxation channel (5D3 : 7F6) --> (5D4 : 7F0). The experimental lifetimes of 5D4 state for all the concentrations of Tb3+ ions are equal and exhibit single exponential decay with highest quantum efficiency which confirms that these glasses can be used for high intensity green emission even at high concentrations of Tb3+ ions.
Plane waves in de Sitter space: Spin-1/2 field
NASA Astrophysics Data System (ADS)
Reza Tanhayi, M.; Mohsenzadeh, M.; Yusofi, E.
2016-06-01
We employ the coordinate-independent plane wave solution in de Sitter space to study the spin-1/2 particle production. The so-called plane waves in the zero-curvature limit reduce to the usual plane waves in flat space. Previously in (Int. J. Mod. Phys. D 24, 1550052 (2015)) we used such modes to study the instability of the de Sitter space, here, by explicit calculation, we study the sipn-1/2 particle creation in de Sitter space caused by mixing modes.
Separability of Gravitational Perturbation in Generalized Kerr-Nut Sitter Space-Time
NASA Astrophysics Data System (ADS)
Oota, Takeshi; Yasui, Yukinori
Generalized Kerr-NUT-de Sitter space-time is the most general space-time which admits a rank-2 closed conformal Killing-Yano tensor. It contains the higher-dimensional Kerr-de Sitter black holes with partially equal angular momenta. We study the separability of gravitational perturbations in the generalized Kerr-NUT-de Sitter space-time. We show that a certain type of tensor perturbations admits the separation of variables. The linearized perturbation equations for the Einstein condition are transformed into the ordinary differential equations of Fuchs type.
Self-Similar Cosmologies in 5D: Spatially Flat Anisotropic Models
NASA Astrophysics Data System (ADS)
Ponce de Leon, J.
In the context of theories of the Kaluza-Klein type, with a large extra dimension, we study self-similar cosmological models in 5D that are homogeneous, anisotropic and spatially flat. The "ladder" to go between the physics in 5D and in 4D is provided by Campbell-Maagard's embedding theorems. We show that the 5D field equations RAB = 0 determine the form of the similarity variable. There are three different possibilities: homothetic, conformal and "wavelike" solutions in 5D. We derive the most general homothetic and conformal solutions to the 5D field equations. They require the extra dimension to be spacelike, and are given in terms of one arbitrary function of the similarity variable and three parameters. The Riemann tensor in 5D is not zero, except in the isotropic limit, which corresponds to the case where the parameters are equal to each other. The solutions can be used as 5D embeddings for a great variety of 4D homogeneous cosmological models, with and without matter, including the Kasner universe. Since the extra dimension is spacelike, the 5D solutions are invariant under the exchange of spatial coordinates. Therefore they also embed a family of spatially inhomogeneous models in 4D. We show that these models can be interpreted as vacuum solutions in braneworld theory. Our work (I) generalizes the 5D embeddings used for FLRW models; (II) shows that anisotropic cosmologies are, in general, curved in 5D, in contrast with FLRW models, which can always be embedded in a 5D Riemann-flat (Minkowski) manifold; and (III) reveals that anisotropic cosmologies can be curved and devoid of matter, both in 5D and in 4D, even when the metric in 5D explicitly depends on the extra coordinate, which is quite different from the isotropic case.
Lecture Notes on Interacting Quantum Fields in de Sitter Space
NASA Astrophysics Data System (ADS)
Akhmedov, E. T.
2013-09-01
We discuss peculiarities of quantum fields in de Sitter (dS) space on the example of the self-interacting massive real scalar, minimally coupled to the gravity background. Nonconformal quantum field theories (QFTs) in dS space show very special infrared behavior, which is not shared by quantum fields neither in flat nor in anti-dS space: in dS space loops are not suppressed in comparison with tree level contributions because there are strong infrared corrections. That is true even for massive fields. Our main concern is the interrelation between these infrared effects, the invariance of the QFT under the dS isometry and the (in)stability of dS invariant states (and of dS space itself) under nonsymmetric perturbations.
Lecture Notes on Interacting Quantum Fields in de Sitter Space
NASA Astrophysics Data System (ADS)
Akhmedov, E. T.
2014-10-01
We discuss peculiarities of quantum fields in de Sitter (dS) space on the example of the self-interacting massive real scalar, minimally coupled to the gravity background. Nonconformal quantum field theories (QFTs) in dS space show very special infrared behavior, which is not shared by quantum fields neither in flat nor in anti-dS space: in dS space loops are not suppressed in comparison with tree level contributions because there are strong infrared corrections. That is true even for massive fields. Our main concern is the interrelation between these infrared effects, the invariance of the QFT under the dS isometry and the (in)stability of dS invariant states (and of dS space itself) under nonsymmetric perturbations.
Gauge dependence in QED amplitudes in expanding de Sitter space
NASA Astrophysics Data System (ADS)
Nicolaevici, Nistor
2016-04-01
We consider first-order transition amplitudes in external fields in QED in the expanding de Sitter space and point out that they are gauge dependent quantities. We examine the gauge variations of the amplitudes assuming a decoupling of the interaction at large times, which allows to conclude that the source of the problem lies in the fact that the frequencies of the modes in the infinite future become independent of the comoving momenta. We show that a possibility to assure the gauge invariance of the external field amplitudes is to restrict to potentials which vanish sufficiently fast at infinite times, and briefly discuss a number of options in the face of the possible gauge invariance violation in the full interacting theory.
Brane induced supersymmetry breaking and de Sitter supergravity
NASA Astrophysics Data System (ADS)
Bandos, Igor; Martucci, Luca; Sorokin, Dmitri; Tonin, Mario
2016-02-01
We obtain a four-dimensional supergravity with spontaneously broken super-symmetry allowing for de Sitter vacua by coupling a superspace action of minimal N = 1, D = 4 supergravity to a locally supersymmetric generalization of the Volkov-Akulov goldstino action describing the dynamics of a space-filling non-BPS 3-brane in N = 1, D = 4 superspace. To the quadratic order in the goldstino field the obtained action coincides with earlier constructions of supergravities with nilpotent superfields, while matching the higher-order contributions will require a non-linear redefinition of fields. In the unitary gauge, in which the goldstino field is set to zero, the action coincides with that of Volkov and Soroka. We also show how a nilpotency constraint on a chiral curvature superfield emerges in this formulation.
Entanglement entropy of α-vacua in de Sitter space
NASA Astrophysics Data System (ADS)
Kanno, Sugumi; Murugan, Jeff; Shock, Jonathan P.; Soda, Jiro
2014-07-01
We consider the entanglement entropy of a free massive scalar field in the one parameter family of α-vacua in de Sitter space by using a method developed by Maldacena and Pimentel. An α-vacuum can be thought of as a state filled with particles from the point of view of the Bunch-Davies vacuum. Of all the α-vacua we find that the entanglement entropy takes the minimal value in the Bunch-Davies solution. We also calculate the asymptotic value of the Rényi entropy and find that it increases as α increases. We argue these features stem from pair condensation within the non-trivial α-vacua where the pairs have an intrinsic quantum correlation.
Energy, momentum and angular momentum conservations in de Sitter gravity
NASA Astrophysics Data System (ADS)
Lu, Jia-An
2016-08-01
In de Sitter (dS) gravity, where gravity is a gauge field introduced to realize the local dS invariance of the matter field, two kinds of conservation laws are derived. The first kind is a differential equation for a dS-covariant current, which unites the canonical energy-momentum (EM) and angular momentum (AM) tensors. The second kind presents a dS-invariant current which is conserved in the sense that its torsion-free divergence vanishes. The dS-invariant current unites the total (matter plus gravity) EM and AM currents. It is well known that the AM current contains an inherent part, called the spin current. Here it is shown that the EM tensor also contains an inherent part, which might be observed by its contribution to the deviation of the dust particle’s world line from a geodesic. All the results are compared to the ordinary Lorentz gravity.
Nonlinear Laplace equation, de Sitter vacua, and information geometry
Loran, Farhang
2005-06-15
Three exact solutions say {phi}{sub 0} of massless scalar theories on Euclidean space, i.e. D=6 {phi}{sup 3}, D=4 {phi}{sup 4} and D=3 {phi}{sup 6} models are obtained which share similar properties. The information geometry of their moduli spaces coincide with the Euclidean AdS{sub 7}, AdS{sub 5} and AdS{sub 4} respectively on which {phi}{sub 0} can be described as a stable tachyon. In D=4 we recognize that the SU(2) instanton density is proportional to {phi}{sub 0}{sup 4}. The original action S[{phi}] written in terms of new scalars {phi}-tilde={phi}-{phi}{sub 0} is shown to be equivalent to an interacting scalar theory on D-dimensional de Sitter background.
Quantum backreactions in slow-roll andde Sitter spacetimes
NASA Astrophysics Data System (ADS)
Losic, Bojan
2006-06-01
approximation of a slowly rolling spacetime may, under reasonable circumstances, be intrinsically sick since higher order contributions are comparable to, or substantially larger than, the linear contributions. In the third and final project, backreactions are considered in a pure de Sitter space whose cosmological constant is generated by the potential of scalar field. The leading order effect of matter backreactions on the gravitational field is considered. The initial value problem for the perturbed Einstein equations is proven to generically possess linearization instabilites. I furthermore show that these linearization instabilities can be avoided by assuming strict de Sitter invariance of the quantum states of the linearized fluctuations. This invariance constraint applies to the entire spectrum of states, from the vacuum to the excited states, and is in that sense much stronger than the usual Poincare invariance of the Minkowski vacuum. Some sketches are presented on how to construct de Sitter invariant states. The main conclusion is that to leading order in their effect on the gravitational field, the quantum states of the matter and metric fluctuations must be de Sitter invariant.
Surviving in a metastable de Sitter space-time
NASA Astrophysics Data System (ADS)
Kashyap, Sitender Pratap; Mondal, Swapnamay; Sen, Ashoke; Verma, Mritunjay
2015-09-01
In a metastable de Sitter space any object has a finite life expectancy beyond which it undergoes vacuum decay. However, by spreading into different parts of the universe which will fall out of causal contact of each other in future, a civilization can increase its collective life expectancy, defined as the average time after which the last settlement disappears due to vacuum decay. We study in detail the collective life expectancy of two comoving objects in de Sitter space as a function of the initial separation, the horizon radius and the vacuum decay rate. We find that even with a modest initial separation, the collective life expectancy can reach a value close to the maximum possible value of 1.5 times that of the individual object if the decay rate is less than 1% of the expansion rate. Our analysis can be generalized to any number of objects, general trajectories not necessarily at rest in the comoving coordinates and general FRW space-time. As part of our analysis we find that in the current state of the universe dominated by matter and cosmological constant, the vacuum decay rate is increasing as a function of time due to accelerated expansion of the volume of the past light cone. Present decay rate is about 3.7 times larger than the average decay rate in the past and the final decay rate in the cosmological constant dominated epoch will be about 56 times larger than the average decay rate in the past. This considerably weakens the lower bound on the half-life of our universe based on its current age.
Interpretational conflicts between the static and non-static forms of the de Sitter metric.
Mitra, Abhas
2012-01-01
The de-Sitter metric is a special form of the non-static Friedmann metric, and appears to be genuinely non-static since it describes the initial exponential expansion of the Big Bang universe. However, the de Sitter metric appears to be perfectly static in the Schwarzschild frame where the vacuum fluid is supposed to be in motion. Here we highlight the conflicts between the static and non-static versions of the de-Sitter metric from a physical perspective. In particular, while the "Principle of Energy Conservation" is honored in one case, the same is badly violated for the other. However, we offer a partial resolution of such conflicts by deriving the static de Sitter metric by solving the relevant field equations. It is seen that, it is the very special vacuum equation of state pressure = -density which results in the static form even when the vacuum fluid is supposed to be in motion. PMID:23213359
Conformally invariant 'massless' spin-2 field in the de Sitter universe
Dehghani, M.; Rouhani, S.; Takook, M. V.; Tanhayi, M. R.
2008-03-15
A massless spin-2 field equation in de Sitter space, which is invariant under the conformal transformation, has been obtained. The framework utilized is the symmetric rank-2 tensor field of the conformal group. Our method is based on the group theoretical approach and six-cone formalism, initially introduced by Dirac. Dirac's six-cone is used to obtain conformally invariant equations on de Sitter space. The solution of the physical sector of massless spin-2 field (linear gravity) in de Sitter ambient space is written as a product of a generalized polarization tensor and a massless minimally coupled scalar field. Similar to the minimally coupled scalar field, for quantization of this sector, the Krein space quantization is utilized. We have calculated the physical part of the linear graviton two-point function. This two-point function is de Sitter invariant and free of pathological large-distance behavior.
Kapteyn and de Sitter; a rare and special teacher-student and coach-player relationship
NASA Astrophysics Data System (ADS)
de Sitter, Wolter Reinold
Measured along the yardstick of subsequent success, Willem de Sitter [1872-1934] was one of Kapteyn's foremost pupils along with van Rhijn, Schilt and Jan Hendrik Oort. From his appointment as professor at Leiden University in 1908 until Kapteyn's death in 1922, de Sitter maintained in close contact with his teacher. Kapteyn was his trusted sounding board and consultant in scientific and administrative matters, as well as academic politics. De Sitter had his ideas on a complete reorganisation and restructuring of Leiden Observatory scrutinized by Kapteyn's experienced judgement, and together they developed ideas and completed a plan of action, including touchy staffing, salary and budgettary aspects. Together they were a formidable team and operated as such. Notes by de Sitter and many letters from Kapteyn illustrate their fruitful relationship.
Filling the Gaps: "The Baby-Sitters Club," the Series Book, and the Learning Reader.
ERIC Educational Resources Information Center
Mackey, Margaret
1990-01-01
Explores the enormous attraction for young readers of series books (such as Nancy Drew, Hardy Boys, and currently "The Baby-Sitters Club"). Discusses what children might learn from such reading, often thought of as pap literature by adults. (SR)
Natural realization of a large extra dimension in 5D supersymmetric theory
NASA Astrophysics Data System (ADS)
Sakamura, Yutaka; Yamada, Yusuke
2014-09-01
An exponentially large extra dimension can be naturally realized by the Casimir energy and the gaugino condensation in 5D supersymmetric theory. The model does not require any hierarchies among the 5D parameters. The key ingredient is an additional modulus other than the radion, which generically exists in 5D supergravity. SUSY is broken at the vacuum, which can be regarded as the Scherk-Schwarz SUSY breaking. We also analyze the mass spectrum and discuss some phenomenological aspects.
Doukas, Jason; Cho, H. T.; Cornell, A. S.; Naylor, Wade
2009-08-15
In this article we present results for tensor graviton modes (in seven dimensions and greater, n{>=}3) for gray-body factors of Kerr-de Sitter black holes and for Hawking radiation from simply rotating (n+4)-dimensional Kerr black holes. Although there is some subtlety with defining the Hawking temperature of a Kerr-de Sitter black hole, we present some preliminary results for emissions assuming the standard Hawking normalization and a Bousso-Hawking-like normalization.
Light bending in Reissner-Nordstrom-de Sitter black hole by Rindler-Ishak method
NASA Astrophysics Data System (ADS)
Heydari-Fard, M.; Mojahed, S.; Rokni, S. Y.
2014-05-01
We investigate the influence of the cosmological constant, Λ, on the bending of light by a charged black hole in a de Sitter spacetime. Despite vanishing of the cosmological constant in the second order null geodesic equation, considering the method introduced by Rindler and Ishak (2007), we obtain an expression for the deflection angle, consistent with previous results for Schwarzschild, Schwarzschild-de Sitter (SdS), and Reissner-Nordstrom (RN) spacetimes.
Contribution of the cosmological constant to the bending of light in Kerr-de Sitter spacetime
NASA Astrophysics Data System (ADS)
Sultana, Joseph
2013-08-01
We examine the effect of the cosmological constant Λ on the angle of deflection of null geodesics in the equatorial plane of the Kerr-de Sitter spacetime. This is done by employing a procedure used recently by Rindler and Ishak to obtain the bending angle of light in the Schwarzschild-de Sitter geometry. We show that this approach yields a contribution from the cosmological constant in the expression for the bending angle.
5D radiating black holes in Einstein-Yang-Mills-Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Ghosh, S. G.
2011-10-01
We derive nonstatic spherically symmetric solutions of a null fluid, in five dimension (5D), to Einstein-Yang-Mills (EYM) equations with the coupling of Gauss-Bonnet (GB) combination of quadratic curvature terms, namely, 5D EYMGB radiating black hole solution. It is shown that, in the limit, we can recover known radiating black hole solutions. The spherically symmetric known 5D static black hole solutions are also retrieved. The effect of the GB term and Yang-Mills (YM) gauge charge on the structure and location of horizons, of the 5D radiating black hole, is also discussed.
Jangravi, Zohreh; Najafi, Mohammad; Shabani, Mohammd
2016-01-01
Background: It is now well-demonstrated that histone demethylases play an important role in developmental controls, cell-fate decisions, and a variety of diseases such as cancer. Lysine-specific demethylase 5D (KDM5D) is a male-specific histone demethylase that specifically demethylates di- and tri-methyl H3K4 at the start site of active gene. In this light, the aim of this study was to investigate isoform/transcript-specific expression profiles of KDM5D in three prostate cancer cell lines, Du-145, LNCaP, and PC3. Methods: Real-time PCR analysis was performed to determine the expression levels of different KDM5D transcripts in the prostate cell lines. A gene regulatory network was established to analyze the gene expression profile. Results: Significantly different expression levels of both isoforms were found among the three cell lines. Interestingly, isoform I was expressed in three cell lines while isoform III did only in DU-145. The expression levels of both isoforms were higher in DU-145 when compared to other cell lines (P<0.0001). The observed expression profile was determined by using regulatory network analyses. Conclusion: The present study, for the first time, not only showed the expression profiles of KDM5D isoforms in prostate cancer cell lines but also evaluated the effects of the gene regulatory network on the expression profile of this gene. PMID:26728332
NASA Astrophysics Data System (ADS)
dos Santos, J. F. M.; Terra, I. A. A.; Astrath, N. G. C.; Guimarães, F. B.; Baesso, M. L.; Nunes, L. A. O.; Catunda, T.
2015-02-01
Trivalent Tb-doped materials exhibit strong emission in the green and weak emission in the UV-blue levels. Usually, this behavior is attributed to the cross relaxation (CR) process. In this paper, the luminescence properties of Tb3+-doped low silica calcium aluminosilicate glasses are analyzed for UV (λexc = 325 nm) and visible (488 nm) excitations. Under 325 nm excitation, the intensity of green luminescence increases proportionally to Tb3+ concentration. However, the blue luminescence intensity is strongly reduced with the increase of concentration from 0.5-15.0 wt. %. In the case of 488 nm excitation, a saturation behavior of the green emission is observed at intensities two orders of magnitude smaller than expected for bleaching of the ground state population. Using a rate equation model, we showed that this behavior can be explained by an excited state absorption cross section two orders of magnitude larger than the ground state absorption. The blue emission is much weaker than expected from our rate equations (325 nm and 488 nm excitation). We concluded that only the CR process cannot explain the overall feature of measured luminescence quenching in the wide range of Tb3+ concentrations. Cooperative upconversion from a pair of excited ions (5D3:5D3 or 5D3:5D4) and other mechanisms involving upper lying states (4f5d, charge transfer, host matrix, defects, etc.) may play a significant role.
The effective rest mass concept and magnetic monopole problem in 5D Theory
NASA Astrophysics Data System (ADS)
Aliyev, B. G.
In this article we have considered and analyzed the new aspects of the rest mass concept of the 5D charged test particle which interacts with the scalar gravitational field and also it was shown that the 5D Ricci identities give us the way to clear the magnetic monopole problem.
Holography and quantum states in elliptic de Sitter space
NASA Astrophysics Data System (ADS)
Halpern, Illan F.; Neiman, Yasha
2015-12-01
We outline a program for interpreting the higher-spin dS/CFT model in terms of physics in the causal patch of a dS observer. The proposal is formulated in "elliptic" de Sitter space d{S}_4/{Z}_2 , obtained by identifying antipodal points in dS 4. We discuss recent evidence that the higher-spin model is especially well-suited for this, since the antipodal symmetry of bulk solutions has a simple encoding on the boundary. For context, we test some other (free and interacting) theories for the same property. Next, we analyze the notion of quantum field states in the non-time-orientable d{S}_4/{Z}_2 . We compare the physics seen by different observers, with the outcome depending on whether they share an arrow of time. Finally, we implement the marriage between higher-spin holography and observers in d{S}_4/{Z}_2 , in the limit of free bulk fields. We succeed in deriving an observer's operator algebra and Hamiltonian from the CFT, but not her S-matrix. We speculate on the extension of this to interacting higher-spin theory.
Altman, Alison B; Pacold, Joseph I; Wang, Jian; Lukens, Wayne W; Minasian, Stefan G
2016-06-14
The electronic structure in the complete series of stable lanthanide sesquioxides, Ln2O3 (Ln = La to Lu, except radioactive Pm), has been evaluated using oxygen K-edge X-ray absorption spectroscopy (XAS) with a scanning transmission X-ray microscope (STXM). The experimental results agree with recent synthetic, spectroscopic and theoretical investigations that provided evidence for 5d orbital involvement in lanthanide bonding, while confirming the traditional viewpoint that there is little Ln 4f and O 2p orbital mixing. However, the results also showed that changes in the energy and occupancy of the 4f orbitals can impact Ln 5d and O 2p mixing, leading to several different bonding modes for seemingly identical Ln2O3 structures. On moving from left to right in the periodic table, abrupt changes were observed for the energy and intensity of transitions associated with Ln 5d and O 2p antibonding states. These changes in peak intensity, which were directly related to the amounts of O 2p and Ln 5d mixing, were closely correlated to the well-established trends in the chemical accessibility of the 4f orbitals towards oxidation or reduction. The unique insight provided by the O K-edge XAS is discussed in the context of several recent theoretical and physical studies on trivalent lanthanide compounds. PMID:26979662
On the R 5d band polarization in rare-earth-transition metal compounds.
Burzo, E; Chioncel, L; Tetean, R; Isnard, O
2011-01-19
Magnetic measurements and band structure calculations were performed on RT(2) and RT(5) compounds, where R is a heavy rare-earth and T = Fe, Co, Ni, Al, as well as on pseudobinary compounds GdCo(2 - x)A(x) (A = Ni, Cu, Si), YFe(2 - x)V(x) and YCo(4 - x)Ni(x)B. The calculated moments per formula unit described well the experimentally determined magnetizations. By considering the 4f-5d-3d exchange interactions, we evaluate the contributions of local 4f-5d and short range 5d-3d interactions to R 5d and Y 4d band polarizations. The 4f-5d induced polarizations are proportional to the De Gennes factor and are the same for a given R and a similar type structure. The R 5d and Y 4d band polarizations induced by R 5d-T3d or Y 4d-T3d hybridizations are proportional to the number of neighbouring T atoms, to a given R, and their magnetic moments. Previous results on the matter are also discussed. PMID:21406851
5 d-4 f luminescence of Er 3+ in YAG:Er 3+
NASA Astrophysics Data System (ADS)
Aleksanyan, Eduard; Harutunyan, Vachagan; Kostanyan, Radik; Feldbach, Eduard; Kirm, Marco; Liblik, Peeter; Makhov, Vladimir N.; Vielhauer, Sebastian
2009-04-01
Interconfigurational 4 f105 d ↔ 4 f11 transitions of the Er 3+ ion in the YAG host were studied under both VUV photon (synchrotron radiation) and electron beam excitation. It was found that the lowest low-spin 5 d level of the Er 3+ ion has a rather large energy gap to the next lower 4 f2D(2) 5/2 crystal-field level, which results in a relatively low rate of nonradiative transitions from this 5 d level leading to the appearance of weak spin-allowed 5 d-4 f luminescence at low temperature. The lowest high-spin 5 d level, from which spin-forbidden 5 d-4 f radiative transitions could occur potentially, is situated only at ˜500 cm -1 above the 4D1/2 level. Such close location allows fast depopulation of the 5 d level resulting in the absence of spin-forbidden 5 d-4 f luminescence and appearance of 4D1/2 4 f-4 f luminescence.
A review of health utilities using the EQ-5D in studies of cardiovascular disease
2010-01-01
Background The EQ-5D has been extensively used to assess patient utility in trials of new treatments within the cardiovascular field. The aims of this study were to review evidence of the validity and reliability of the EQ-5D, and to summarise utility scores based on the use of the EQ-5D in clinical trials and in studies of patients with cardiovascular disease. Methods A structured literature search was conducted using keywords related to cardiovascular disease and EQ-5D. Original research studies of patients with cardiovascular disease that reported EQ-5D results and its measurement properties were included. Results Of 147 identified papers, 66 met the selection criteria, with 10 studies reporting evidence on validity or reliability and 60 reporting EQ-5D responses (VAS or self-classification). Mean EQ-5D index-based scores ranged from 0.24 (SD 0.39) to 0.90 (SD 0.16), while VAS scores ranged from 37 (SD 21) to 89 (no SD reported). Stratification of EQ-5D index scores by disease severity revealed that scores decreased from a mean of 0.78 (SD 0.18) to 0.51 (SD 0.21) for mild to severe disease in heart failure patients and from 0.80 (SD 0.05) to 0.45 (SD 0.22) for mild to severe disease in angina patients. Conclusions The published evidence generally supports the validity and reliability of the EQ-5D as an outcome measure within the cardiovascular area. This review provides utility estimates across a range of cardiovascular subgroups and treatments that may be useful for future modelling of utilities and QALYs in economic evaluations within the cardiovascular area. PMID:20109189
Hamiltonian Formulation of the 5-D Kaluza-Klein Model and Test-Particle Motion
NASA Astrophysics Data System (ADS)
Lacquaniti, Valentino; Montani, Giovanni
2008-09-01
We examine the ADM reformulation of the 5-D KK model: the dimensional reduction is provided to commute with the ADM splitting and we show how the time component of the gauge vector is given by combination of the Lagrangian multipliers for the 5-D gravitational field. We consider 5D particles motion and after dimensional reduction the definition of charge is recovered within electrodynamic coupling. A time-varying fine structure constant is recognized because an extra scalar field is present in the 4-D theory.
Induced inflation from a 5D purely kinetic scalar field formalism on warped product spaces
NASA Astrophysics Data System (ADS)
Madriz Aguilar, J. E.
2008-01-01
Considering a separable and purely kinetic 5D scalar field we investigate the induction of 4D scalar potentials on a 4D constant foliation on the class of 5D warped product space-times. We obtain a quantum confinement of the inflaton modes given naturally from the model for at least a class of warping factors. We can recover a 4D inflationary scenario where the inflationary potential is geometrically induced from 5D and the effective equation of state in 4D that includes the effect of the inflaton field and the induced matter is Peff≃-ρeff.
Auxiliary Conformally Invariant Higher-Spin Field in de Sitter Space
NASA Astrophysics Data System (ADS)
Elmizadeh, M.; Tanhayi, M. R.
2016-03-01
We employ de Sitter isometry to study a mixed symmetric rank-3 tensor field in de Sitter space by finding the field equation, solution and two-point function which are conformally invariant. It is proved that such a tensor field plays a key role in conformal theory of linear gravity (Binegar et al., Phys. Rev. D 27, 2249, 1983) . In de Sitter space from the group theoretical point of view this kind of tensor could associate with two unitary irreducible representations (UIR) of the de Sitter group (Takook et al., J.Math. Phys. 51, 032503, 2010), which one representation has a flat limit, namely, in zero curvature coincides to the UIR of Poincaré group, however, the second one which is named as auxiliary field, becomes significant in the study of conformal gravity in de Sitter background. We show that the rank-3 tensor solution can be written in terms of a massless minimally coupled scalar field and also the related two-point function is a function of a massless minimally coupled scalar two-point function.
5D Einstein-Maxwell solitons and concentric rotating dipole black rings
Yazadjiev, Stoytcho S.
2008-09-15
We discuss the application of the solitonic techniques to the 5D Einstein-Maxwell gravity. As an illustration we construct a new exact solution describing two concentric rotating dipole black rings. The properties of the solution are investigated.
Exact Solutions of the 5d Space-Time Universe and Their Implications
NASA Astrophysics Data System (ADS)
Fukui, Takao
2008-09-01
What can the exact solutions of the 5D STM Universe imply when they are compared to the field equations of a Corrected Metric Tensor Universe? The comparison implies the possibility of clarifying the meaning of the cosmological term.
Fermions in the 5D gravity-scalar standing wave braneworld
NASA Astrophysics Data System (ADS)
Gogberashvili, Merab; Midodashvili, Pavle
2014-09-01
In this paper, we investigate localization problem for spinor fields within the (5D) standing wave braneworld with the bulk real scalar field and show that there exist normalizable fermion field zero modes on the brane.
Validation of a 2.5D CFD model for cylindrical gas–solids fluidized beds
Li, Tingwen
2015-09-25
The 2.5D model recently proposed by Li et al. (Li, T., Benyahia, S., Dietiker, J., Musser, J., and Sun, X., 2015. A 2.5D computational method to simulate cylindrical fluidized beds. Chemical Engineering Science. 123, 236-246.) was validated for two cylindrical gas-solids bubbling fluidized bed systems. Different types of particles tested under various flow conditions were simulated using the traditional 2D model and the 2.5D model. Detailed comparison against the experimental measurements on solid concentration and velocity were conducted. Comparing to the traditional Cartesian 2D flow simulation, the 2.5D model yielded better agreement with the experimental data especially for the solid velocity prediction in the column wall region.
Validation of a 2.5D CFD model for cylindrical gas–solids fluidized beds
Li, Tingwen
2015-09-25
The 2.5D model recently proposed by Li et al. (Li, T., Benyahia, S., Dietiker, J., Musser, J., and Sun, X., 2015. A 2.5D computational method to simulate cylindrical fluidized beds. Chemical Engineering Science. 123, 236-246.) was validated for two cylindrical gas-solids bubbling fluidized bed systems. Different types of particles tested under various flow conditions were simulated using the traditional 2D model and the 2.5D model. Detailed comparison against the experimental measurements on solid concentration and velocity were conducted. Comparing to the traditional Cartesian 2D flow simulation, the 2.5D model yielded better agreement with the experimental data especially for the solidmore » velocity prediction in the column wall region.« less
Correspondence Between Dgp Brane Cosmology and 5d Ricci-Flat Cosmology
NASA Astrophysics Data System (ADS)
Ping, Yongli; Xu, Lixin; Liu, Hongya
We discuss the correspondence between the DGP brane cosmology and 5D Ricci-flat cosmology by letting their metrics equal each other. By this correspondence, a specific geometrical property of the arbitrary integral constant I in DGP metric is given and it is related to the curvature of 5D bulk. At the same time, the relation of arbitrary functions μ and ν in a class of Ricci-flat solutions is obtained from DGP brane metric.
Pathways to relativistic curved momentum spaces: de Sitter case study
NASA Astrophysics Data System (ADS)
Amelino-Camelia, Giovanni; Gubitosi, Giulia; Palmisano, Giovanni
2016-01-01
Several arguments suggest that the Planck scale could be the characteristic scale of curvature of momentum space. As other recent studies, we assume that the metric of momentum space determines the condition of on-shellness while the momentum space affine connection governs the form of the law of composition of momenta. We show that the possible choices of laws of composition of momenta are more numerous than the possible choices of affine connection on a momentum space. This motivates us to propose a new prescription for associating an affine connection to momentum composition, which we compare to the one most used in the recent literature. We find that the two prescriptions lead to the same picture of the so-called κ-momentum space, with de Sitter (dS) metric and κ-Poincaré connection. We then show that in the case of “proper dS momentum space”, with the dS metric and its Levi-Civita connection, the two prescriptions are inequivalent. Our novel prescription leads to a picture of proper dS momentum space which is DSR-relativistic and is characterized by a commutative law of composition of momenta, a possibility for which no explicit curved momentum space picture had been previously found. This momentum space can serve as laboratory for the exploration of the properties of DSR-relativistic theories which are not connected to group-manifold momentum spaces and Hopf algebras, and is a natural test case for the study of momentum spaces with commutative, and yet deformed, laws of composition of momenta.
Wave-like solutions for Bianchi type I cosmologies in 5D
NASA Astrophysics Data System (ADS)
Ponce de Leon, J.
2008-10-01
We derive exact solutions to the vacuum Einstein field equations in 5D, under the assumption that (i) the line element in 5D possesses self-similar symmetry, in the classical understanding of Sedov, Taub and Zeldovich, and that (ii) the metric tensor is diagonal and independent of the coordinates for ordinary 3D space. These assumptions lead to three different types of self-similarity in 5D: homothetic, conformal and 'wave-like'. In this work we present the most general wave-like solutions to the 5D field equations. Using the standard technique based on Campbell's theorem, they generate a large number of anisotropic cosmological models of Bianchi type I, which can be applied to our universe after the big bang, when anisotropies could have played an important role. We present a complete review of all possible cases of self-similar anisotropic cosmologies in 5D. Our analysis extends a number of previous studies on wave-like solutions in 5D with spatial spherical symmetry.
Riemann correlator in de Sitter including loop corrections from conformal fields
NASA Astrophysics Data System (ADS)
Fröb, Markus B.; Roura, Albert; Verdaguer, Enric
2014-07-01
The Riemann correlator with appropriately raised indices characterizes in a gauge-invariant way the quantum metric fluctuations around de Sitter spacetime including loop corrections from matter fields. Specializing to conformal fields and employing a method that selects the de Sitter-invariant vacuum in the Poincaré patch, we obtain the exact result for the Riemann correlator through order H4/mp4. The result is expressed in a manifestly de Sitter-invariant form in terms of maximally symmetric bitensors. Its behavior for both short and long distances (sub- and superhorizon scales) is analyzed in detail. Furthermore, by carefully taking the flat-space limit, the explicit result for the Riemann correlator for metric fluctuations around Minkowki spacetime is also obtained. Although the main focus is on free scalar fields (our calculation corresponds then to one-loop order in the matter fields), the result for general conformal field theories is also derived.
Riemann correlator in de Sitter including loop corrections from conformal fields
Fröb, Markus B.; Verdaguer, Enric
2014-07-01
The Riemann correlator with appropriately raised indices characterizes in a gauge-invariant way the quantum metric fluctuations around de Sitter spacetime including loop corrections from matter fields. Specializing to conformal fields and employing a method that selects the de Sitter-invariant vacuum in the Poincaré patch, we obtain the exact result for the Riemann correlator through order H{sup 4}/m{sub p}{sup 4}. The result is expressed in a manifestly de Sitter-invariant form in terms of maximally symmetric bitensors. Its behavior for both short and long distances (sub- and superhorizon scales) is analyzed in detail. Furthermore, by carefully taking the flat-space limit, the explicit result for the Riemann correlator for metric fluctuations around Minkowki spacetime is also obtained. Although the main focus is on free scalar fields (our calculation corresponds then to one-loop order in the matter fields), the result for general conformal field theories is also derived.
Dark fluid or cosmological constant: Why there are different de Sitter-type spacetimes
NASA Astrophysics Data System (ADS)
Nouri-Zonoz, M.; Koohbor, J.; Ramezani-Aval, H.
2015-03-01
Many different forms of the de Sitter metric in different coordinate systems are used in the general relativity literature. Two of them are the most common: the static form and the cosmological (exponentially expanding) form. The staticity and nonstationarity of these two different forms are traced back to the noncomoving and comoving nature of the corresponding coordinate systems. In this paper, using the quasi-Maxwell form of the Einstein field equations and a definition of static spacetimes based upon them, we look at these two different forms of the same solution from a new perspective which classifies them as a special case in a general one-parameter family of solutions. Specifically it is proved that, irrespective of the spacetime symmetry, a one-element perfect fluid in any frame noncomoving with the fluid could be the source of a static spacetime, only if its equation of state is that of a dark fluid, namely, p =-ρ =const . These static solutions, which include the well-known de Sitter spacetime, are called de Sitter-type spacetimes. To answer the question posed in the title, we consider static axially and cylindrically symmetric de Sitter-type spacetimes and their dynamic (cosmological) versions. It is shown how despite the seemingly natural expectation based on the presence of Λ as their only parameter, the nonspherical expansions of these genuinely different solutions should be expected indeed. To the best of our knowledge the dynamic version of the cylindrically symmetric de Sitter-type spacetime is introduced here for the first time. Finally it is noted that the identification of the geometric term Λ gi j with a perfect fluid with equation of state p =-ρ =const , although mathematically consistent, obscures the crucial role of the (dark) fluid's velocity in defining a preferred (comoving) coordinate system in de Sitter-type spacetimes.
Site-specific strong ground motion prediction using 2.5-D modelling
NASA Astrophysics Data System (ADS)
Narayan, J. P.
2001-08-01
An algorithm was developed using the 2.5-D elastodynamic wave equation, based on the displacement-stress relation. One of the most significant advantages of the 2.5-D simulation is that the 3-D radiation pattern can be generated using double-couple point shear-dislocation sources in the 2-D numerical grid. A parsimonious staggered grid scheme was adopted instead of the standard staggered grid scheme, since this is the only scheme suitable for computing the dislocation. This new 2.5-D numerical modelling avoids the extensive computational cost of 3-D modelling. The significance of this exercise is that it makes it possible to simulate the strong ground motion (SGM), taking into account the energy released, 3-D radiation pattern, path effects and local site conditions at any location around the epicentre. The slowness vector (py) was used in the supersonic region for each layer, so that all the components of the inertia coefficient are positive. The double-couple point shear-dislocation source was implemented in the numerical grid using the moment tensor components as the body-force couples. The moment per unit volume was used in both the 3-D and 2.5-D modelling. A good agreement in the 3-D and 2.5-D responses for different grid sizes was obtained when the moment per unit volume was further reduced by a factor equal to the finite-difference grid size in the case of the 2.5-D modelling. The components of the radiation pattern were computed in the xz-plane using 3-D and 2.5-D algorithms for various focal mechanisms, and the results were in good agreement. A comparative study of the amplitude behaviour of the 3-D and 2.5-D wavefronts in a layered medium reveals the spatial and temporal damped nature of the 2.5-D elastodynamic wave equation. 3-D and 2.5-D simulated responses at a site using a different strike direction reveal that strong ground motion (SGM) can be predicted just by rotating the strike of the fault counter-clockwise by the same amount as the azimuth of
Gravitationally induced adiabatic particle production: from big bang to de Sitter
NASA Astrophysics Data System (ADS)
de Haro, Jaume; Pan, Supriya
2016-08-01
In the background of a flat homogeneous and isotropic space–time, we consider a scenario of the Universe driven by the gravitationally induced ‘adiabatic’ particle production with constant creation rate. We have shown that this Universe attains a big bang singularity in the past and at late-time it asymptotically becomes de Sitter. To clarify this model Universe, we performed a dynamical analysis and found that the Universe attains a thermodynamic equilibrium in this late de Sitter phase. Finally, for the first time, we have discussed the possible effects of ‘adiabatic’ particle creations in the context of loop quantum cosmology.
Nonperturbative semiclassical stability of de Sitter spacetime for small metric deviations
NASA Astrophysics Data System (ADS)
Fröb, Markus B.; Papadopoulos, Demetrios B.; Roura, Albert; Verdaguer, Enric
2013-03-01
We consider the linearized semiclassical Einstein equations for small deviations around de Sitter spacetime including the vacuum polarization effects of conformal fields. Employing the method of order reduction, we find the exact solutions for general metric perturbations (of scalar, vector and tensor type). Our exact (nonperturbative) solutions show clearly that in this case de Sitter is stable with respect to small metric deviations and a late-time attractor. Furthermore, they also reveal a breakdown of perturbative solutions for a sufficiently long evolution inside the horizon. Our results are valid for any conformal theory, even self-interacting ones with arbitrarily strong coupling.
More on the covariant retarded Green's function for the electromagnetic field in de Sitter spacetime
Higuchi, Atsushi; Lee, Yen Cheong; Nicholas, Jack R.
2009-11-15
In a recent paper 2 it was shown in examples that the covariant retarded Green's functions in certain gauges for electromagnetism and linearized gravity can be used to reproduce field configurations correctly in spite of the spacelike nature of past infinity in de Sitter spacetime. In this paper we extend the work of Ref. 2 concerning the electromagnetic field and show that the covariant retarded Green's function with an arbitrary value of the gauge parameter reproduces the electromagnetic field from two opposite charges at antipodal points of de Sitter spacetime.
Distinguishing de Sitter universe from thermal Minkowski spacetime by Casimir-Polder-like force
NASA Astrophysics Data System (ADS)
Tian, Zehua; Jing, Jiliang
2014-07-01
We demonstrate that the static ground state atom, which interacts with a conformally coupled massless scalar field in the de Sitter invariant vacuum, can obtain a position-dependent energy-level shift and this shift could cause a Casimir-Polder-like force on it. Interestingly no such force arises on the inertial atom bathed in a thermal radiation in the Minkowski universe. Thus, although the energy-level shifts of the static atom for these two cases are structurally the same, whether the energy-level shift causes the Casimir-Polder-like force, in principle, could be as an indicator to distinguish de Sitter universe from the thermal Minkowski spacetime.
NASA Astrophysics Data System (ADS)
Görnitz, Th.; Weizsäcker, C. F. V.
The theory of urs (basic two-valued observables) is used to describe particles in cosmic space-time. Cosmic position space is described as S3, interpreted as a homogeneous space of SU(2). An expanding model of the universe is locally approximated by de Sitter spaces. Irreducible representations of the de Sitter group are explicitly constructed in ur theory. From these, Poincaré group representations in Minkowski space with well-defined rest mass are deduced by a special rule of contraction.
Fermion production in dipolar electric field on de Sitter expanding universe
NASA Astrophysics Data System (ADS)
Bǎloi, Mihaela-Andreea; Crucean, Cosmin
2015-12-01
The production of fermions in dipolar electric fields on de Sitter universe is studied. The amplitude and probability of pair production are computed using the exact solution of the Dirac equation in de Sitter spacetime. The form of the dipolar fields is established using the conformal invariance of the Maxwell equations. We obtain that the momentum conservation law is broken in the process of pair production in dipolar electric fields. Also we establish that there are nonvanishing probabilities for processes in which the helicity is conserved/nonconserved. The Minkowski limit is recovered when the expansion factor becomes zero.
Annihilation of the scalar pair into a photon in a de Sitter universe
NASA Astrophysics Data System (ADS)
Băloi, Mihaela-Andreea
2016-05-01
The annihilation of massive scalar particles in one photon in de Sitter expanding universe is studied, using perturbative QED. The amplitude and probability corresponding to this process is computed using the exact solutions of the Klein-Gordon and Maxwell equations on de Sitter geometry. Our results show that the expression of the total probability of photon emission is a function dependent on the ratio mass/expansion factor. We perform a graphical study of the total probability in terms of the parameter mass/expansion factor, showing that this effect is significant only in strong gravitational fields. We also obtain that the total probability for this process vanishes in the Minkowski limit.
Fermion production in dipolar electric field on de Sitter expanding universe
Băloi, Mihaela-Andreea Crucean, Cosmin
2015-12-07
The production of fermions in dipolar electric fields on de Sitter universe is studied. The amplitude and probability of pair production are computed using the exact solution of the Dirac equation in de Sitter spacetime. The form of the dipolar fields is established using the conformal invariance of the Maxwell equations. We obtain that the momentum conservation law is broken in the process of pair production in dipolar electric fields. Also we establish that there are nonvanishing probabilities for processes in which the helicity is conserved/nonconserved. The Minkowski limit is recovered when the expansion factor becomes zero.
Solution of the Dyson-Schwinger equation on a de Sitter background in the infrared limit
NASA Astrophysics Data System (ADS)
Akhmedov, E. T.; Burda, Ph.
2012-08-01
We propose an ansatz which solves the Dyson-Schwinger equation for the real scalar fields in a Poincaré patch of de Sitter space in the infrared limit. The Dyson-Schwinger equation for this ansatz reduces to the kinetic equation, if one considers scalar fields from the principal series. Solving the latter equation we show that under the adiabatic switching on and then off of the coupling constant, the Bunch-Davies vacuum relaxes in future infinity to the state with the flat Gibbons-Hawking density of out-Jost harmonics on top of the corresponding de Sitter invariant out vacuum.
Mission analysis and systems design of a near-term and far-term pole-sitter mission
NASA Astrophysics Data System (ADS)
Heiligers, Jeannette; Ceriotti, Matteo; McInnes, Colin R.; Biggs, James D.
2014-01-01
This paper provides a detailed mission analysis and systems design of a near-term and far-term pole-sitter mission. The pole-sitter concept was previously introduced as a solution to the poor temporal resolution of polar observations from highly inclined, low Earth orbits and the poor high-latitude coverage from geostationary orbit. It considers a spacecraft that is continuously above either the north or south pole and, as such, can provide real-time, continuous and hemispherical coverage of the polar regions. Being on a non-Keplerian orbit, a continuous thrust is required to maintain the pole-sitter position. For this, two different propulsion strategies are proposed, which result in a near-term pole-sitter mission using solar electric propulsion (SEP) and a far-term pole-sitter mission where the SEP thruster is hybridized with a solar sail. For both propulsion strategies, minimum propellant pole-sitter orbits are designed. In order to maximize the spacecraft mass at the start of the operations phase of the mission, the transfer from Earth to the pole-sitter orbit is designed and optimized assuming either a Soyuz or an Ariane 5 launch. The maximized mass upon injection into the pole-sitter orbit is subsequently used in a detailed mass budget analysis that will allow for a trade-off between mission lifetime and payload mass capacity. Also, candidate payloads for a range of applications are investigated. Finally, transfers between north and south pole-sitter orbits are considered to overcome the limitations in observations due to the tilt of the Earth's rotational axis that causes the poles to be alternately situated in darkness. It will be shown that in some cases these transfers allow for propellant savings, enabling a further extension of the pole-sitter mission.
The validity of EQ-5D US preference weights in liver transplant candidates and recipients.
Russell, Robert T; Feurer, Irene D; Wisawatapnimit, Panarut; Pinson, C Wright
2009-01-01
Health utility instruments assess patients' valuation of specific health states, which can be converted to quality-adjusted life years for cost-utility analysis. Data from the EQ-5D, a generic health-related quality of life questionnaire from EuroQoL, can be reported as 5 health status scores or as a single health preference weight (HPW). US population-based HPWs were published by Shaw and colleagues in 2005 (Med Care 2005;43:203-220). Our aim was to test the validity of US EQ-5D HPWs and health status scores in liver transplant patients. EQ-5D scores were converted to HPWs with Shaw et al.'s model. Data were stratified by measurement period: pretransplant period, early posttransplant period (< or =12 months), intermediate posttransplant period (13-36 months), and late posttransplant period (>36 months). EQ-5D scores were compared to specific, hypothesized Short Form 36 Health Survey, Center for Epidemiologic Studies Depression Scale, and Beck Anxiety Inventory scores that were identified a priori on the basis of construct similarity. Criterion-related and construct validity were tested with nonparametric methods. Two hundred eighty-five adults participated (113 in the pretransplant period, 60 in the early posttransplant period, 47 in the intermediate posttransplant period, and 65 in the late posttransplant period), and follow-up averaged 36 +/- 36 months. Eighty-one percent of the hypothesized relationships between EQ-5D and gold-standard scales were strong (r > or = |0.5|, P < 0.001), and the remainder were moderate (r > |0.3|, P < 0.001). Differences between pretransplant and posttransplant EQ-5D HPWs were statistically significant. In conclusion, EQ-5D dimensions and the health utility index generated from Shaw's US population preference weights demonstrated criterion-related and construct validity in liver transplant patients. It is a valid instrument for cost-utility analysis in this setting. PMID:19109831
Non-local thermodynamic equilibrium 1.5D modeling of red giant stars
Young, Mitchell E.; Short, C. Ian
2014-05-20
Spectra for two-dimensional (2D) stars in the 1.5D approximation are created from synthetic spectra of one-dimensional (1D) non-local thermodynamic equilibrium (NLTE) spherical model atmospheres produced by the PHOENIX code. The 1.5D stars have the spatially averaged Rayleigh-Jeans flux of a K3-4 III star while varying the temperature difference between the two 1D component models (ΔT {sub 1.5D}) and the relative surface area covered. Synthetic observable quantities from the 1.5D stars are fitted with quantities from NLTE and local thermodynamic equilibrium (LTE) 1D models to assess the errors in inferred T {sub eff} values from assuming horizontal homogeneity and LTE. Five different quantities are fit to determine the T {sub eff} of the 1.5D stars: UBVRI photometric colors, absolute surface flux spectral energy distributions (SEDs), relative SEDs, continuum normalized spectra, and TiO band profiles. In all cases except the TiO band profiles, the inferred T {sub eff} value increases with increasing ΔT {sub 1.5D}. In all cases, the inferred T {sub eff} value from fitting 1D LTE quantities is higher than from fitting 1D NLTE quantities and is approximately constant as a function of ΔT {sub 1.5D} within each case. The difference between LTE and NLTE for the TiO bands is caused indirectly by the NLTE temperature structure of the upper atmosphere, as the bands are computed in LTE. We conclude that the difference between T {sub eff} values derived from NLTE and LTE modeling is relatively insensitive to the degree of the horizontal inhomogeneity of the star being modeled and largely depends on the observable quantity being fit.
Physical and geometrical aspects of de sitter interior of a gravastar
NASA Astrophysics Data System (ADS)
Morawiec, Pawel Jan
The principal motivation for the investigations reported in this thesis is the gravastar model for physical black holes. According to this model the final state of the gravitational collapse of cold super-dense stars with the mass greater than some critical value is a non-singular object called a gravastar. This thesis presents results related to the various aspects of the de Sitter interior of a gravastar. The main object of the research was a generalized rotating interior of a gravastar. It was shown that the rotation, characterized by the vorticity, is localized on the vortex line. The metric under considerations is the de Sitter metric, however in some variant of the oblate spheroidal coordinates. Additionally a cosmic string on the rotation axis is present. This new result is the de Sitter version of the Mazur string, which was obtained from the four dimensional Levi-Civita metric as the generalization of the three-dimensional cosmic string by Adler and Jackiw. Also, using analogy between rotation in the superfluid and the magnetic field we gave another example of the Cosmic No Hair Theorem, this time "no magnetic fields in de Sitter space". But we also have shown that when the de Sitter event horizon is replaced by a thin shell (with a finite thickness), as it is in the gravastar model, the non-vanishing magnetic field could be present. To our knowledge these are new results. In this thesis we have studied behavior of the massless Dirac field as an example of a matter field in the de Sitter spacetime in the vicinity of an event horizon. We found convenient to work in the frame of the optical geometry of the de Sitter space as it is related to the metric in the static coordinates through a conformal Weyl rescaling and the dynamics of the massless Dirac fields is conformally invariant. The fact that the spatial part of the metric in the optical geometry of de Sitter space is the constant negative curvature Lobachevski space (the Euclidean ant-de Sitter space
Interplay of 3 d-5 d interactions in high-TC osmium-based double perovskites
NASA Astrophysics Data System (ADS)
Taylor, A. E.; Calder, S.; Morrow, R.; Woodward, P. M.; Yan, J. Q.; Winn, B.; Lumsden, M. D.; Christianson, A. D.
2015-03-01
In 3d-5d systems the strongly magnetic 3d orbitals and extended 5d orbitals with enhanced spin-orbit coupling lead to a range of high TC magnetic states and novel behavior not present in systems consisting solely of 3d or 5d ions. The two distinct octahedral sites in double perovskites A2 BB 'O6 allow an ordered 3d-5d structure to form, providing a variety of systems to be investigated. Unravelling the interactions controlling these systems, however, is an open challenge. The highest known TC in such a system, 725K, is found in insulator Sr2CrOsO6. This questions the theory for high-TCs in systems such as TC=400K Sr2FeReO6 which relies on half-metallic behavior. To unravel the nature of the interactions in 3d-5d systems, we have studied the series of compounds Sr2 X OsO6. We have utilized elastic and inelastic neutron scattering to probe the spin states in the systems, and therefore test predictions that the magnetic interactions are controlled by a frustrated AFM Heisenberg model. By studying the series, we are able to relate changes in the spin wave spectrum to dramatic changes in the magnetic order from TN = 95 K antiferromagnetism to TC = 725 K ferrimagnetism.
The minimum clinically important difference for EQ-5D index: a critical review.
Coretti, Silvia; Ruggeri, Matteo; McNamee, Paul
2014-04-01
The European Quality of Life-5 Dimensions Questionnaire (EQ-5D) is the most common instrument to value health outcomes under the patient's perspective. Several studies have investigated whether observed changes are meaningful to patients, using a variety of approaches to estimate the minimum clinically important difference (MCID). This study provides an overview of the state of art of the estimation of the MCID for the three-level EQ-5D index based on the UK scoring algorithm, critically assessing the available evidence. The interest in estimation of MCID for the EQ-5D has been increasing in recent years. However, some additional standardization in the estimation procedures may be of value, in order to enhance the ability to make comparisons across measures and disease areas. Further methodological research might also contribute to reducing gaps between theory and practice. PMID:24625040
Exact Solutions of Embedding the 4d Universe in a 5d Einstein Manifold
NASA Astrophysics Data System (ADS)
Meng, Xin-He; Ren, Jie; Zhang, Hong-Guang
One of the simplest ways to extend 4D cosmological models is to add another spatial dimension to make them 5D. In particular, it has been shown that the simplest of such 5D models, i.e. one in which the right-hand side of the Einstein equation is empty, induces a 4D nonempty universe. Accordingly, the origin of matter in a real 4D universe might be mathematically attributed to the existence of one (fictitious) extra spatial dimension. Here we consider the case of an empty 5D universe possessing a cosmological constant Λ and obtain exact solutions for both positive and negative values of the Λ. It is seen that such a model can naturally reduce to a power law ΛCDM model for the real universe. Further, it can be seen that the arbitrary constants and functions appearing in this model are endowed with definite physical meanings.
Covariant and infrared-free graviton two-point function in de Sitter spacetime
NASA Astrophysics Data System (ADS)
Pejhan, Hamed; Rahbardehghan, Surena
2016-02-01
In this paper, the two-point function of linearized gravitons on de Sitter (dS) space is presented. Technically, respecting the dS ambient space notation, the field equation is given by the coordinate-independent Casimir operators of the de Sitter group. Analogous to the quantization of the electromagnetic field in Minkowski space, the field equation admits gauge solutions. The notation allows us to exhibit the formalism of Gupta-Bleuler triplets for the present field in exactly the same manner as it occurs for the electromagnetic field. In this regard, centering on the spin-two part (the traceless part, Kt), the field solution is written as a product of a generalized polarization tensor and a minimally coupled massless scalar field. Then, admitting a de Sitter-invariant vacuum through the so-called "Krein space quantization," the de Sitter fully covariant two-point function is calculated. This function is interestingly free of pathological large distance behavior (infrared divergence). Moreover, the spin-zero part (the pure-trace part; Kp t) of the field is discussed in this paper. It is shown that the implications of the dS group unitary irreducible representations restrict the gauge-fixing parameter to the optimal value, which remarkably results in the pure-trace part be written in terms of a conformally coupled massless scalar field.
The Booth Sitters of Santa Fe's Indian Market: Making and Maintaining Authenticity
ERIC Educational Resources Information Center
Bernstein, Bruce
2007-01-01
In this article, the author addresses the burden of non-Native expectation on Native artists, highlighting issues of authenticity, creation, and public display. The author writes about the booth sitters hired by collectors to sit--sometimes all night--and wait for the official opening of the annual Indian Market in Santa Fe, New Mexico. He focuses…
A new method of researching fermion tunneling from the Vaidya-Bonner de Sitter black hole
NASA Astrophysics Data System (ADS)
Lin, Kai; Yang, Shu-Zheng
2009-06-01
Using the general tortoise coordinate transformation, we research the fermion tunneling of the Vaidya-Bonner de Sitter black hole via a semi-classical method and finally obtain the right surface gravity, Hawking temperature and tunneling rate near the event horizon and cosmical horizon.
On the solution of the Dirac equation in de Sitter space
NASA Astrophysics Data System (ADS)
Klishevich, V. V.; Tyumentsev, V. A.
2005-10-01
It is shown that the maximal number of first-order symmetry operators for the Dirac equation (including spin symmetries), both in arbitrary signature flat space and in de Sitter space, is equal. The isomorphic representation of 11-dimensional nonlinear symmetry algebra (W-algebra) of first-order operators for the Dirac operator in flat space and de Sitter space is considered. The algebra is an extension of the Lie algebra of the group of pseudo-orthogonal rotations and this extension is unique. We have found all linear Lie subalgebras in the nonlinear algebra that satisfy the conditions of the noncommutative integration theorem. Using one subalgebra we have integrated the Dirac equation in the generalized spherical system of coordinates and have constructed the complete class of exact solutions. The solution is found by a method that differs from the variable separation method and is new in the literature. The massive particle spectrum, models of particle into antiparticle transmutation, the disappearance of particles and the quantization conditions of the motion are discussed. One can use the results of the paper to pose the boundary problem for the Dirac equation in de Sitter space if the interval is used in the boundary condition. As an example, we consider a model of asymptotically flat space that is glued from the de Sitter space and flat space. We interpret the model as a gravitational well or barrier.
Interpretational conflicts between the static and non-static forms of the de Sitter metric
Mitra, Abhas
2012-01-01
The de-Sitter metric is a special form of the non-static Friedmann metric, and appears to be genuinely non-static since it describes the initial exponential expansion of the Big Bang universe. However, the de Sitter metric appears to be perfectly static in the Schwarzschild frame where the vacuum fluid is supposed to be in motion. Here we highlight the conflicts between the static and non-static versions of the de-Sitter metric from a physical perspective. In particular, while the “Principle of Energy Conservation” is honored in one case, the same is badly violated for the other. However, we offer a partial resolution of such conflicts by deriving the static de Sitter metric by solving the relevant field equations. It is seen that, it is the very special vacuum equation of state pressure = –density which results in the static form even when the vacuum fluid is supposed to be in motion. PMID:23213359
Relative unitary implementability of perturbed quantum field dynamics on de-Sitter space
NASA Astrophysics Data System (ADS)
Poon, Gary K.
In this article, we study the quantum dynamics of a Klein-Gordon field on de-Sitter space. We prove time evolution is not unitarily implementable. We also consider a Klein-Gordon field perturbed by a local potential V. In this case we prove that the deviation from the V = 0 dynamics is unitarily implementable.
General Solution of Massless Spin-{3}/{2} Field in de Sitter Universe
NASA Astrophysics Data System (ADS)
Parsamehr, S.
2016-02-01
This paper is devoted to a general solution of the massless spin-{3}/{2} field in de Sitter space without any conditions in ambient space formalism. A general solution of the second-order field equation can be written in terms of a vector-spinor polarization state and a massless conformally coupled scalar field.
Instability of higher-dimensional charged black holes in the de sitter world.
Konoplya, R A; Zhidenko, A
2009-10-16
We have shown that higher-dimensional Reissner-Nordström-de Sitter black holes are gravitationally unstable for large values of the electric charge and cosmological constant in D>or=7 space-time dimensions. We have found the shape of the slightly perturbed black hole at the threshold point of instability. PMID:19905685
On the weak field approximation of the de Sitter gauge theory of gravity
NASA Astrophysics Data System (ADS)
Ma, Meng-Sen; Huang, Chao-Guang
2013-01-01
The weak field approximation of a model of de Sitter gauge theory of gravity is studied in two cases. Without torsion and spin current, the model cannot give the right non-relativistic approximation unless the density is a constant. With small torsion, a satisfactory Newtonian approximation can be obtained.
a 5d Noncompact Kaluza-Klein Cosmology in the Presence of Null Perfect Fluid
NASA Astrophysics Data System (ADS)
Farajollahi, Hossein; Amiri, Hamed
For the description of the early inflation and acceleration expansion of the universe that are compatible with observational data, the 5D noncompact Kaluza-Klein cosmology is investigated. It is proposed that the 5D space is filled with a null perfect fluid, resulting in a perfect fluid in a 4D universe, plus one along the fifth dimension. By analyzing the reduced field equations for the flat FRW model, we show the early inflationary behavior and the current acceleration of the universe.
Active Dirac neutrinos via SU(2) L doublets in 5d
NASA Astrophysics Data System (ADS)
Fujimoto, Yukihiro; Hasegawa, K.; Nagasawa, Tomoaki; Nishiwaki, Kenji; Sakamoto, Makoto; Tatsumi, Kentaro
2016-06-01
We propose a new mechanism to generate minuscule active neutrino masses in a five-dimensional (5d) spacetime of an interval without introducing SU(2) L singlet neutrinos. Under asymmetric boundary conditions on the two end points, a bulk mass for a 5d fermion allows a Dirac particle with a tiny mass eigenvalue. Implementing this mechanism, which provides us a new tool for building neutrino mass models, to the standard model gauge structure is possible when all the gauge bosons and the Higgs boson are localized on one of the branes.
Enhanced spin-phonon-electronic coupling in a 5d oxide.
Calder, S; Lee, J H; Stone, M B; Lumsden, M D; Lang, J C; Feygenson, M; Zhao, Z; Yan, J-Q; Shi, Y G; Sun, Y S; Tsujimoto, Y; Yamaura, K; Christianson, A D
2015-01-01
Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions that drive novel emergent behaviour. This is exemplified in osmates that host metal-insulator transitions where magnetic order appears intimately entwined. Here we consider such a material, the 5d perovskite NaOsO3, and observe a coupling between spin and phonon manifested in a frequency shift of 40 cm(-1), the largest measured in any material. The anomalous modes are shown to involve solely Os-O interactions and magnetism is revealed as the driving microscopic mechanism for the phonon renormalization. The magnitude of the coupling in NaOsO3 is primarily due to a property common to all 5d materials: the large spatial extent of the ion. This allows magnetism to couple to phonons on an unprecedented scale and in general offers multiple new routes to enhanced coupled phenomena in 5d materials. PMID:26608626
Enhanced spin-phonon-electronic coupling in a 5d oxide
NASA Astrophysics Data System (ADS)
Calder, S.; Lee, J. H.; Stone, M. B.; Lumsden, M. D.; Lang, J. C.; Feygenson, M.; Zhao, Z.; Yan, J.-Q.; Shi, Y. G.; Sun, Y. S.; Tsujimoto, Y.; Yamaura, K.; Christianson, A. D.
2015-11-01
Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions that drive novel emergent behaviour. This is exemplified in osmates that host metal-insulator transitions where magnetic order appears intimately entwined. Here we consider such a material, the 5d perovskite NaOsO3, and observe a coupling between spin and phonon manifested in a frequency shift of 40 cm-1, the largest measured in any material. The anomalous modes are shown to involve solely Os-O interactions and magnetism is revealed as the driving microscopic mechanism for the phonon renormalization. The magnitude of the coupling in NaOsO3 is primarily due to a property common to all 5d materials: the large spatial extent of the ion. This allows magnetism to couple to phonons on an unprecedented scale and in general offers multiple new routes to enhanced coupled phenomena in 5d materials.
Simulation of Laser Wake Field Acceleration using a 2.5D PIC Code
NASA Astrophysics Data System (ADS)
An, W. M.; Hua, J. F.; Huang, W. H.; Tang, Ch. X.; Lin, Y. Z.
2006-11-01
A 2.5D PIC simulation code is developed to study the LWFA( Laser WakeField Acceleration ). The electron self-injection and the generation of mono-energetic electron beam in LWFA is briefly discussed through the simulation. And the experiment of this year at SILEX-I laser facility is also introduced.
Enhanced spin-phonon-electronic coupling in a 5d oxide
Calder, Stuart A.; Yamaura, K.; Tsujimoto, Y.; Sun, Y. S.; Stone, Matthew B.; Shi, Y. G.; Lang, Jonathan; Christianson, Andrew D.; Lumsden, Mark D.; Lee, Jun Hee; Feygenson, Mikhail; Zhao, Zhiying; Yan, Jiaqiang
2015-11-26
Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions that drive novel emergent behaviour. This is exemplified in osmates that host metal insulator transitions where magnetic order appears intimately entwined. Here we consider such a material, the 5d perovskite NaOsO_{3}, and observe a coupling between spin and phonon manifested in a frequency shift of 40 cm 1, the largest measured in any material. The anomalous modes are shown to involve solely Os O interactions and magnetism is revealed as the driving microscopic mechanism for the phonon renormalization. The magnitude of the coupling in NaOsO_{3} is primarily due to a property common to all 5d materials: the large spatial extent of the ion. This allows magnetism to couple to phonons on an unprecedented scale and in general offers multiple new routes to enhanced coupled phenomena in 5d materials.
Enhanced spin-phonon-electronic coupling in a 5d oxide
Calder, Stuart A.; Yamaura, K.; Tsujimoto, Y.; Sun, Y. S.; Stone, Matthew B.; Shi, Y. G.; Lang, Jonathan; Christianson, Andrew D.; Lumsden, Mark D.; Lee, Jun Hee; et al
2015-11-26
Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions that drive novel emergent behaviour. This is exemplified in osmates that host metal insulator transitions where magnetic order appears intimately entwined. Here we consider such a material, the 5d perovskite NaOsO3, and observe a coupling between spin and phonon manifested in a frequency shift of 40 cm 1, the largest measured in any material. The anomalous modes are shown to involve solely Os O interactions and magnetism is revealed as the driving microscopic mechanism formore » the phonon renormalization. The magnitude of the coupling in NaOsO3 is primarily due to a property common to all 5d materials: the large spatial extent of the ion. This allows magnetism to couple to phonons on an unprecedented scale and in general offers multiple new routes to enhanced coupled phenomena in 5d materials.« less
Dyonic Reissner-Nordström black hole: extended Dirac quantization from 5D invariants
NASA Astrophysics Data System (ADS)
Romero, Jesús Martín; Bellini, Mauricio
2015-10-01
The aim of present work is to extend the application of Weitzenböck Induced Matter Theory (WIMT) to a dyonic Reissner-Nordström Black Hole (RNBH), by proposing a condition compatible with a quantization relation between gravitational mass and both magnetic and electric charges from a geometric product defined as an invariant in 5D.
Brans-Dicke cosmology in 4D from scalar-vacuum in 5D
NASA Astrophysics Data System (ADS)
Ponce de Leon, J.
2010-03-01
We show that Brans-Dicke (BD) theory in 5D may explain the present cosmic accelerated expansion without recurring to matter fields in 5D or dark energy in 4D. Without making any assumption on the nature of the extra coordinate or the matter content in 5D, here we demonstrate that the vacuum BD field equations in 5D are equivalent, on every hypersurface orthogonal to the extra dimension, to a BD theory in 4D with a self interacting potential and an effective matter field. The potential is not introduced by hand, instead the reduction procedure provides an expression that determines its shape up to a constant of integration. It also establishes the explicit formulae for the effective matter in 4D. In the context of FRW cosmologies, we show that the reduced BD theory gives rise to models for accelerated expansion of a matter-dominated universe which are consistent with current observations and with a decelerating radiation-dominated epoch.
Enhanced spin-phonon-electronic coupling in a 5d oxide
Calder, S.; Lee, J. H.; Stone, M. B.; Lumsden, M. D.; Lang, J. C.; Feygenson, M.; Zhao, Z.; Yan, J.-Q.; Shi, Y. G.; Sun, Y. S.; Tsujimoto, Y.; Yamaura, K.; Christianson, A. D.
2015-01-01
Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions that drive novel emergent behaviour. This is exemplified in osmates that host metal–insulator transitions where magnetic order appears intimately entwined. Here we consider such a material, the 5d perovskite NaOsO3, and observe a coupling between spin and phonon manifested in a frequency shift of 40 cm−1, the largest measured in any material. The anomalous modes are shown to involve solely Os–O interactions and magnetism is revealed as the driving microscopic mechanism for the phonon renormalization. The magnitude of the coupling in NaOsO3 is primarily due to a property common to all 5d materials: the large spatial extent of the ion. This allows magnetism to couple to phonons on an unprecedented scale and in general offers multiple new routes to enhanced coupled phenomena in 5d materials. PMID:26608626
Comparison of SF-6D and EQ-5D Scores in Patients With Breast Cancer
Yousefi, Mahmood; Najafi, Safa; Ghaffari, Shahram; Mahboub-Ahari, Alireza; Ghaderi, Hossein
2016-01-01
Background Utility values are a key component of a cost-utility analysis. The EQ-5D and SF-6D are two commonly used measures for deriving utilities. Of particular importance is assessing the performance of these instruments in terms of validity. Objectives This study aimed to compare the performance of the EQ-5D and the SF-6D in different states of breast cancer. Patients and Methods This was a cross-sectional study of 163 patients with breast cancer who attended the breast cancer subspecialty clinic affiliated with the breast cancer research center (BCRC) at ACECR, in Tehran, Iran, and were consecutively recruited. Patients completed several questionnaires, including the EQ-5D, SF-36, and general questions regarding their demographic characteristics. Utility values for different states of breast cancer were obtained using predetermined algorithms for the EQ-5D and SF-6D. The distribution of the utility values and the differences between the different states for both instruments were statistically assessed. Furthermore, the agreement between the two instruments was evaluated using intra-class correlation coefficients and Bland-Altman plots. Results The mean and median EQ-5D utility scores for the total sample were 0.685 and 0.761, respectively. The mean SF-6D utility score for the total sample was 0.653, and the median utility score was 0.640. The mean utility values of the EQ-5D for “state P,” “state R,” “state S,” and “state M” were estimated as 0.674, 0.718, 0.730, and 0.552, respectively. The SF-6D provided mean utility values of 0.638, 0.677, 0.681, and 0.587 for those states. Both instruments assigned statistically significant (P < 0.01) scores for different states. The intra-class correlation for the two measures was 0.677 (95% confidence interval (CI): 0.558 - 0.764). The Bland-Altman plot indicated a better agreement on the higher values and that at higher values, the EQ-5D yields a higher score than the SF-6D; this relationship was
A 5D holographic dark energy in DGP-BRANE cosmology
NASA Astrophysics Data System (ADS)
Farajollahi, H.; Ravanpak, A.
2014-02-01
This paper is aimed to investigate 5D holographic dark energy (HDE) in DGP-Brane cosmology by employing a combination of Sne Ia, BAO and CMB observational data and constraining cosmological parameters. The FRW dynamics for the normal branch ( ɛ=+1) solution of induced gravity brane-world model is taken with the assumption that matter in 5D bulk is HDE such that its holographic nature is reproduced effectively in 4D universe. In the HDE model, we used Hubble horizon as IR cutoff instead of future event horizon. This way, while the model predicts current universe acceleration, it also removes the problem of circular reasoning and causality observed in using future event horizon as IR cutoff.
Quintessence interacting dark energy and a scalar dark fluid from 5D vacuum
NASA Astrophysics Data System (ADS)
Reyes, L. M.; Madriz Aguilar, José Edgar
2011-11-01
Considering a five-dimensional (5D) spacetime empty of matter, we develop a procedure from which an interacting scalar field and its potential are induced on our 4D spacetime by the 5D geometry. We use the procedure to derive a new 4D interacting quintessence scenario, where the quintessence field, its potential and the interaction between the dark matter and dark energy components have a geometrical origin. The mass of the interacting quintessence field depends on the extra dimension, thus giving more freedom to avoid conflicts with nucleosynthesis. Then, inspired from some scalar dark matter models, we extend the geometrical formalism to derive a novel 4D late-time cosmological scenario, where the whole dark sector of the universe (scalar dark matter plus dark energy) admits a unified description by a single geometrical scalar field.
Late time cosmic acceleration from vacuum Brans-Dicke theory in 5D
NASA Astrophysics Data System (ADS)
Ponce de Leon, J.
2010-05-01
We show that the scalar-vacuum Brans-Dicke equations in 5D are equivalent to Brans-Dicke theory in 4D with a self-interacting potential and an effective matter field. The cosmological implication, in the context of FRW models, is that the observed accelerated expansion of the universe comes naturally from the condition that the scalar field is not a ghost, i.e. ω > -3/2. We find an effective matter-dominated 4D universe which shows accelerated expansion if -3/2 < ω < -1. We study the question of whether accelerated expansion can be made compatible with large values of ω, within the framework of a 5D scalar-vacuum Brans-Dicke theory with variable, instead of constant, parameter ω. In this framework, and based on a general class of solutions of the field equations, we demonstrate that accelerated expansion is incompatible with large values of ω.
Area functional relation for 5D-Gauss-Bonnet-AdS black hole
NASA Astrophysics Data System (ADS)
Pradhan, Parthapratim
2016-08-01
We present area (or entropy) functional relation for multi-horizons five dimensional (5D) Einstein-Maxwell-Gauss-Bonnet-AdS black hole. It has been observed by exact and explicit calculation that some complicated function of two or three horizons area is mass-independent whereas the entropy product relation is not mass-independent. We also study the local thermodynamic stability of this black hole. The phase transition occurs at certain condition. Smarr mass formula and first law of thermodynamics have been derived. This mass-independent relation suggests they could turn out to be an universal quantity and further helps us to understanding the nature of black hole entropy (both interior and exterior) at the microscopic level. In the "Appendix", we have derived the thermodynamic products for 5D Einstein-Maxwell-Gauss-Bonnet black hole with vanishing cosmological constant.
Optimal design analysis for thermal performance of high power 2.5D package
NASA Astrophysics Data System (ADS)
Xiaoyang, Liu; He, Ma; Daquan, Yu; Wenlu, Chen; Xiaolong, Wu
2016-03-01
Based on ANSYS and Icepak softwares, the numerical analysis method is used to build up the thermal analysis model of the 2.5D package, which contains a high power CPU chip. The focus of the research is on the determination of the contributing factors and their effects on the thermal resistance and heat distribution of the package. The parametric analysis illustrates that the substrate conductivity, TIM conductivity and fin height are more crucial for heat conduction in the package. Furthermore, these major parameters are compared and analyzed by orthogonal tests, and the optimal solution for 2.5D integration is proposed. The factors' influence patterns on thermal resistance, obtained in this article, could be utilized as a thermal design reference. Project supported by the National S & T Major Projects (No. 2011ZX02709-2) and the China National Science Foundation (No. 61176098).
A 2.5D Computational Method to Simulate Cylindrical Fluidized Beds
Li, Tingwen; Benyahia, Sofiane; Dietiker, Jeff; Musser, Jordan; Sun, Xin
2015-02-17
In this paper, the limitations of axisymmetric and Cartesian two-dimensional (2D) simulations of cylindrical gas-solid fluidized beds are discussed. A new method has been proposed to carry out pseudo-two-dimensional (2.5D) simulations of a cylindrical fluidized bed by appropriately combining computational domains of Cartesian 2D and axisymmetric simulations. The proposed method was implemented in the open-source code MFIX and applied to the simulation of a lab-scale bubbling fluidized bed with necessary sensitivity study. After a careful grid study to ensure the numerical results are grid independent, detailed comparisons of the flow hydrodynamics were presented against axisymmetric and Cartesian 2D simulations. Furthermore, the 2.5D simulation results have been compared to the three-dimensional (3D) simulation for evaluation. This new approach yields better agreement with the 3D simulation results than with axisymmetric and Cartesian 2D simulations.
Numerical study of leptogenesis in a 5D split fermion model with bulk neutrinos
Kuismanen, Heidi; Vilja, Iiro; Maalampi, Jukka
2011-03-01
We study numerically a 5D hybrid model which incorporates a split fermion scenario and bulk neutrinos. We perform a Monte Carlo analysis of the model in order to find the regions in the parameter space allowing for the realization of the leptogenesis. We find that higher order Yukawa terms must be included in order for the model to produce a CP violation and net baryon number sufficient for the creation of the observed baryon asymmetry of the Universe.
Adjustment of foreign EQ-5D-3L utilities can increase their transferability
Oddershede, Lars; Petersen, Karin Dam
2015-01-01
Background Foreign utilities of the EQ-5D-3L (3-level version of the EuroQol-5 Dimension of health questionnaire) are not readily transferrable to economic evaluations conducted from a national perspective. It has been advised to avoid transferring mean utilities from one country to another without adjusting them; yet no such method exists. Purpose The present study aimed to develop a method for adjusting mean utilities to increase their transferability from one country to another. Methods Seven datasets containing EQ-5D-3L answers were valued using value sets from four countries: the UK, the Netherlands, Germany, and Spain. Hereby, seven mean utility values were obtained for each country. This allowed for three pairwise comparisons: 1) UK mean values vs Dutch mean values; 2) UK mean values vs German mean values; and 3) UK mean values vs Spanish mean values. For each of these three comparisons, a regression model was fitted using the mean UK utilities as the dependent variable and the other country’s mean utilities as the independent variable. The coefficients from the three regression models were validated using results from a published article containing mean utilities obtained by valuing the EQ-5D-3L data using all four value sets. Results The findings suggested that adjustment of foreign utilities may increase transferability between countries where value sets are not comparable. It was possible to adjust the mean utilities valued by the Dutch and German value sets to make them reflect mean UK utilities as there were substantial differences between these value sets. Transferability of the Spanish mean utility values was not improved as the Spanish and UK value sets are sufficiently similar. Conclusion It is feasible to adjust foreign mean utilities of the EQ-5D-3L to make them reflect national preferences for health. PMID:26719715
Dynamics of the universe as a ``test 3-brane'' in a 5D bulk
NASA Astrophysics Data System (ADS)
Farajollahi, Hossein; Ravanpak, Arvin
2011-08-01
In this paper we study the dynamics of a 5D bulk space-time with our universe as a "test 3-brane" located in the bulk, an idealized model of a topological object whose physical properties is negligible in comparison with that of the bulk. Our universe experiences acceleration and its equation of state parameter crosses the phantom divide line due to the geometry of the bulk space-time.
Some cosmological solutions of 5D Einstein equations with dark spinor condensate
NASA Astrophysics Data System (ADS)
Lee, Tae Hoon
2012-05-01
We study the 5D Einstein gravity equations with dark spinor condensate, and under the cylinder condition we find an exponentially expanding cosmological solution for the scale factor of our universe, even without a cosmological constant. The stability condition for the solution is given. Some power-law cosmological solutions are also derived when bulk matter sources in the form of a perfect fluid are additionally introduced.
Waveform tomography in 2.5D: Parameterization for crooked-line acquisition geometry
NASA Astrophysics Data System (ADS)
Smithyman, B. R.; Clowes, R. M.
2013-05-01
A method for 2.5D viscoacoustic waveform tomography that can be applied to generate 2D models of velocity and attenuation from inversion of refraction waveforms on land seismic reflection data acquired along crooked roads is developed. It is particularly useful for typical crustal reflection surveys. First-arrival travel time tomography is applied using a 3D method, but with constraints on the intermediate 3D velocity model; the result is the starting model for the next step. A 2.5D frequency-domain full-waveform inversion stage parameterizes 3D geometry in the seismic source and receiver arrays, with the assumption that the velocity and attenuation models are homogeneous in the out-of-plane direction. This approach results in superior results compared to a strictly 2D approach when the acquisition line is crooked, with a moderate increase in computational cost. A case study using data acquired in the Nechako Basin in south-central British Columbia, Canada, exemplifies and validates the procedure. The velocity model derived from 2.5D waveform tomography is compared with that from a previous study in which 2D waveform tomography was applied to the same data set and with results from 3D travel time tomography. The resolution and accuracy of the velocity model from 2.5D waveform tomography are demonstrated to be greater than those from travel time or 2D waveform tomography. A model of viscoacoustic attenuation, which was not possible in the 2D case, is also generated. These models are interpreted jointly to highlight features of geological interest, such as a sedimentary basin, basement rocks, and faults, from surface to about 3 km depth.
Simultaneous denoising and reconstruction of 5D seismic data via damped rank-reduction method
NASA Astrophysics Data System (ADS)
Chen, Yangkang; Zhang, Dong; Jin, Zhaoyu; Chen, Xiaohong; Zu, Shaohuan; Huang, Weilin; Gan, Shuwei
2016-06-01
The Cadzow rank-reduction method can be effectively utilized in simultaneously denoising and reconstructing 5D seismic data that depends on four spatial dimensions. The classic version of Cadzow rank-reduction method arranges the 4D spatial data into a level-four block Hankel/Toeplitz matrix and then applies truncated singular value decomposition (TSVD) for rank-reduction. When the observed data is extremely noisy, which is often the feature of real seismic data, traditional TSVD cannot be adequate for attenuating the noise and reconstructing the signals. The reconstructed data tends to contain a significant amount of residual noise using the traditional TSVD method, which can be explained by the fact that the reconstructed data space is a mixture of both signal subspace and noise subspace. In order to better decompose the block Hankel matrix into signal and noise components, we introduced a damping operator into the traditional TSVD formula, which we call the damped rank-reduction method. The damped rank-reduction method can obtain a perfect reconstruction performance even when the observed data has extremely low signal-to-noise ratio (SNR). The feasibility of the improved 5D seismic data reconstruction method was validated via both 5D synthetic and field data examples. We presented comprehensive analysis of the data examples and obtained valuable experience and guidelines in better utilizing the proposed method in practice. Since the proposed method is convenient to implement and can achieve immediate improvement, we suggest its wide application in the industry.
Simultaneous denoising and reconstruction of 5-D seismic data via damped rank-reduction method
NASA Astrophysics Data System (ADS)
Chen, Yangkang; Zhang, Dong; Jin, Zhaoyu; Chen, Xiaohong; Zu, Shaohuan; Huang, Weilin; Gan, Shuwei
2016-09-01
The Cadzow rank-reduction method can be effectively utilized in simultaneously denoising and reconstructing 5-D seismic data that depend on four spatial dimensions. The classic version of Cadzow rank-reduction method arranges the 4-D spatial data into a level-four block Hankel/Toeplitz matrix and then applies truncated singular value decomposition (TSVD) for rank reduction. When the observed data are extremely noisy, which is often the feature of real seismic data, traditional TSVD cannot be adequate for attenuating the noise and reconstructing the signals. The reconstructed data tend to contain a significant amount of residual noise using the traditional TSVD method, which can be explained by the fact that the reconstructed data space is a mixture of both signal subspace and noise subspace. In order to better decompose the block Hankel matrix into signal and noise components, we introduced a damping operator into the traditional TSVD formula, which we call the damped rank-reduction method. The damped rank-reduction method can obtain a perfect reconstruction performance even when the observed data have extremely low signal-to-noise ratio. The feasibility of the improved 5-D seismic data reconstruction method was validated via both 5-D synthetic and field data examples. We presented comprehensive analysis of the data examples and obtained valuable experience and guidelines in better utilizing the proposed method in practice. Since the proposed method is convenient to implement and can achieve immediate improvement, we suggest its wide application in the industry.
Automatic 2.5-D Facial Landmarking and Emotion Annotation for Social Interaction Assistance.
Zhao, Xi; Zou, Jianhua; Li, Huibin; Dellandrea, Emmanuel; Kakadiaris, Ioannis A; Chen, Liming
2016-09-01
People with low vision, Alzheimer's disease, and autism spectrum disorder experience difficulties in perceiving or interpreting facial expression of emotion in their social lives. Though automatic facial expression recognition (FER) methods on 2-D videos have been extensively investigated, their performance was constrained by challenges in head pose and lighting conditions. The shape information in 3-D facial data can reduce or even overcome these challenges. However, high expenses of 3-D cameras prevent their widespread use. Fortunately, 2.5-D facial data from emerging portable RGB-D cameras provide a good balance for this dilemma. In this paper, we propose an automatic emotion annotation solution on 2.5-D facial data collected from RGB-D cameras. The solution consists of a facial landmarking method and a FER method. Specifically, we propose building a deformable partial face model and fit the model to a 2.5-D face for localizing facial landmarks automatically. In FER, a novel action unit (AU) space-based FER method has been proposed. Facial features are extracted using landmarks and further represented as coordinates in the AU space, which are classified into facial expressions. Evaluated on three publicly accessible facial databases, namely EURECOM, FRGC, and Bosphorus databases, the proposed facial landmarking and expression recognition methods have achieved satisfactory results. Possible real-world applications using our algorithms have also been discussed. PMID:26316289
Evidence from Lake Baikal for Siberian glaciation during oxygen-isotope substage 5d
Karabanov, E.B.; Prokopenko, A.A.; Williams, D.F.; Colman, Steven M.
1998-01-01
The paleoclimatic record from bottom sediments of Lake Baikal (eastern Siberia) reveals new evidence for an abrupt and intense glaciation during the initial part of the last interglacial period (isotope substage 5d). This glaciation lasted about 12 000 yr from 117 000 to 105 000 yr BP according to correlation with the SPEC-MAP isotope chronology. Lithological and biogeochemical evidence of glaciation from Lake Baikal agrees with evidence for the advance of ice sheet in northwestern Siberia during this time period and also with cryogenic features within the strata of Kazantzevo soils in Southern Siberia. The severe 5d glaciation in Siberia was caused by dramatic cooling due to the decrease in solar insolation (as predicted by the model of insulation changes for northern Asia according to Milankovich theory) coupled with western atmospheric transport of moisture from the opea areas of Northern Atlantic and Arctic seas (which became ice-free due to the intense warming during preceeding isotope substage 5e). Other marine and continental records show evidence for cooling during 5d, but not for intense glaciation. Late Pleistocene glaciations in the Northern Hemisphere may have begun in northwestern Siberia.
Regularized Fully 5D Reconstruction of Cardiac Gated Dynamic SPECT Images.
Niu, Xiaofeng; Yang, Yongyi; Jin, Mingwu; Wernick, Miles N; King, Michael A
2010-01-01
In our recent work, we proposed an image reconstruction procedure aimed to unify gated imaging and dynamic imaging in nuclear cardiac imaging. With this procedure the goal is to obtain an image sequence from a single acquisition which shows simultaneously both cardiac motion and tracer distribution change over the course of imaging. In this work, we further develop and demonstrate this procedure for fully 5D (3D space plus time plus gate) reconstruction in gated, dynamic cardiac SPECT imaging, where the challenge is even greater without the use of multiple fast camera rotations. For 5D reconstruction, we develop and compare two iterative algorithms: one is based on the modified block sequential regularized EM (BSREM-II) algorithm, and the other is based on the one-step late (OSL) algorithm. In our experiments, we simulated gated cardiac imaging with the NURBS-based cardiac-torso (NCAT) phantom and Tc99m-Teboroxime as the imaging agent, where acquisition with the equivalent of only three full camera rotations was used during the course of a 12-minute postinjection period. We conducted a thorough evaluation of the reconstruction results using a number of quantitative measures. Our results demonstrate that the 5D reconstruction procedure can yield gated dynamic images which show quantitative information for both perfusion defect detection and cardiac motion. PMID:24049191
Universal spin-1/2 fermion field localization on a 5D braneworld
NASA Astrophysics Data System (ADS)
Barbosa-Cendejas, Nandinii; Malagón-Morejón, Dagoberto; Mora-Luna, Refugio Rigel
2015-07-01
In this work we present a refined method for the localization of spin- fermions on the 5D braneworld paradigm. We begin by proposing a more natural ansatz for the Yukawa coupling in the 5D bulk fermionic action, that guarantees the localization of the ground states for the 4D fermions with right- or left-chirality. In earlier works the existing freedom on the form of the Yukawa coupling was used in a rather speculative way depending on the type of model, the ansatz proposed in this work is suitable for thin and thick braneworld models and can be applied to branes made of a scalar field or not and in this sense it is the more natural choice. Furthermore, we show that the fermion ground states localization allow us to show the absence of tachyonic modes in the left- and right-chiral Kaluza-Klein mass spectrum. More precisely, we show that localization of gravity in the 5D braneworld implies the localization of the spin- fermions.
Late-time structure of the Bunch-Davies de Sitter wavefunction
Anninos, Dionysios; Anous, Tarek; Freedman, Daniel Z.; Konstantinidis, George
2015-11-30
We examine the late time behavior of the Bunch-Davies wavefunction for interacting light fields in a de Sitter background. We use perturbative techniques developed in the framework of AdS/CFT, and analytically continue to compute tree and loop level contributions to the Bunch-Davies wavefunction. We consider self-interacting scalars of general mass, but focus especially on the massless and conformally coupled cases. We show that certain contributions grow logarithmically in conformal time both at tree and loop level. We also consider gauge fields and gravitons. The four-dimensional Fefferman-Graham expansion of classical asymptotically de Sitter solutions is used to show that the wavefunction contains no logarithmic growth in the pure graviton sector at tree level. Finally, assuming a holographic relation between the wavefunction and the partition function of a conformal field theory, we interpret the logarithmic growths in the language of conformal field theory.
Perturbative approach to the problem of particle production in electric field on de Sitter universe
NASA Astrophysics Data System (ADS)
Crucean, Cosmin; Băloi, Mihaela-Andreea
2016-04-01
In this paper, we study the problem of scalar particle production in external electric field in de Sitter geometry. The total probability is calculated using the previously obtained result in [M. A. Băloi, Mod. Phys. Lett. A 29, 1450138 (2014)] for transition amplitude in external electric field on de Sitter space. Then we make a graphical study of the total probability in terms of the ratio mass of the particle/expansion factor. Our results show that the probability depend on the direction in which the particles are emitted and that the probability becomes maximum when particles are emitted on the direction of the electric field. In the Minkowski limit, we obtain that the probability is vanishing.
Isometry generators in momentum representation of the Dirac theory on the de Sitter spacetime
NASA Astrophysics Data System (ADS)
Cotăescu, Ion I.; Băltăţeanu, Doru-Marcel
2015-11-01
In this paper, it is shown that the covariant representation (CR) transforming the Dirac field under de Sitter isometries is equivalent to a direct sum of two unitary irreducible representations (UIRs) of the Sp(2, 2) group transforming alike the particle and antiparticle field operators in momentum representation. Their basis generators and Casimir operators are written down for the first time finding that these representations are equivalent to an UIR from the principal series whose canonical labels are determined by the fermion mass and spin. The properties of the conserved observables (i.e. one-particle operators) associated to the de Sitter isometries via Noether theorem and of the corresponding Pauli-Lubanski type operator are also pointed out.
Gravitational lensing effects of a Reissner-Nordstrom-de Sitter black hole
NASA Astrophysics Data System (ADS)
Zhao, Fan; Tang, Jianfeng; He, Feng
2016-06-01
We investigate the influence of cosmological constant Λ on gravitational lensing. By the method of an elliptic integral, we give out the solution to the null geodesic equation in the Reissner-Nordstrom-de Sitter spacetime. The deflection angle of light is obtained by studying the intrinsic geometry of the spatial equatorial plane in the Reissner-Nordstrom-de Sitter spacetime. By applying the expansion of elliptic integrals, we find the deflection angle in the weak field limit and in the strong field limit, respectively. We find the angular position and magnification of images and discuss its behavior under changed Λ . At last, we give out the higher-order term in the strong field limit.
Equilibration of a quantum field in de Sitter space-time
NASA Astrophysics Data System (ADS)
Albrecht, Andreas; Holman, R.; Richard, Benoit J.
2015-02-01
We address the following question: To what extent can a quantum field tell if it has been placed in de Sitter space? Our approach is to use the techniques of nonequilibrium quantum field theory to compute the time evolution of a state which starts off in flat space for (conformal) times η <η0 and then evolves in a de Sitter background turned on instantaneously at η =η0. We find that the answer depends on what quantities one examines. We study a range of them, all based on two-point correlation functions, and analyze which ones approach the standard Bunch-Davies values over time. The outcome of this analysis suggests that the nature of the equilibration process in this system is similar to that in more familiar systems.
Late-time structure of the Bunch-Davies de Sitter wavefunction
NASA Astrophysics Data System (ADS)
Anninos, Dionysios; Anous, Tarek; Freedman, Daniel Z.; Konstantinidis, George
2015-11-01
We examine the late time behavior of the Bunch-Davies wavefunction for interacting light fields in a de Sitter background. We use perturbative techniques developed in the framework of AdS/CFT, and analytically continue to compute tree and loop level contributions to the Bunch-Davies wavefunction. We consider self-interacting scalars of general mass, but focus especially on the massless and conformally coupled cases. We show that certain contributions grow logarithmically in conformal time both at tree and loop level. We also consider gauge fields and gravitons. The four-dimensional Fefferman-Graham expansion of classical asymptotically de Sitter solutions is used to show that the wavefunction contains no logarithmic growth in the pure graviton sector at tree level. Finally, assuming a holographic relation between the wavefunction and the partition function of a conformal field theory, we interpret the logarithmic growths in the language of conformal field theory.
Evidence for a bound on the lifetime of de Sitter space
NASA Astrophysics Data System (ADS)
Freivogel, Ben; Lippert, Matthew
2008-12-01
Recent work has suggested a surprising new upper bound on the lifetime of de Sitter vacua in string theory. The bound is parametrically longer than the Hubble time but parametrically shorter than the recurrence time. We investigate whether the bound is satisfied in a particular class of de Sitter solutions, the KKLT vacua. Despite the freedom to make the supersymmetry breaking scale exponentially small, which naively would lead to extremely stable vacua, we find that the lifetime is always less than about exp(1022) Hubble times, in agreement with the proposed bound. This result, however, is contingent on several estimates and assumptions; in particular, we rely on a conjectural upper bound on the Euler number of the Calabi-Yau fourfolds used in KKLT compactifications.
Restoration of the covariant gauge α in the initial field of gravity in de Sitter spacetime
Cheong, Lee Yen; Yan, Chew Xiao
2014-03-05
The gravitational field generated by a mass term and the initial surface through covariant retarded Green's function for linearized gravity in de Sitter spacetime was studied recently [4, 5] with the covariant gauges set to β = 2/3 and α = 5/3. In this paper we extend the work to restore the gauge parameter α in the field coming from the initial data using the method of shifting the parameter. The α terms in the initial field cancels exactly with the one coming from the source term. Consequently, the correct field configuration, with two equal mass points moving in its geodesic, one located at the North pole and another one located at the South pole, is reproduced in the whole manifold of de Sitter spacetime.
Slipher's Redshifts as Support for de Sitter's Model and the Discovery of the Dynamic Universe
NASA Astrophysics Data System (ADS)
Nussbaumer, H.
2013-04-01
Of the first two relativistic world models, only the one by de Sitter predicted redshifted spectra from far away astronomical objects. Slipher's redshifts therefore seemed to arbitrate against Einstein's model which made no such predictions. Both models were trying to describe a static universe. However, Lemaître found that de Sitter's construct resulted in a spatially inhomogeneous universe. He then opted for a model that corresponded to Einstein's closed, curved universe but allowed the radius of curvature to change with time. Slipher's redshifts suggested to him that the universe is dynamic and expanding. We also discuss the respective merits of Friedman and Lemaître in revealing the dynamic nature of the universe.
Lifting of Flat Directions of the MSSM in de Sitter Background
Garbrecht, Bjoern
2008-11-23
We derive one-loop effective potentials in de Sitter background for scalar, fermion and gauge-boson loops. The results are applied to flat directions of the MSSM. It is found that due to Yukawa couplings, a lifting mass term of order of the Hubble rate arises. The lifting contributions mediated by the gauge couplings are found to cancel at leading order in the Hubble rate.
Point splitting renormalization of Schwinger induced current in de Sitter spacetime
NASA Astrophysics Data System (ADS)
Hayashinaka, Takahiro; Yokoyama, Jun'ichi
2016-07-01
The covariant and gauge invariant calculation of the current expectation value in the homogeneous electric field in 1+3 dimensional de Sitter spacetime is shown. The result accords with previous work obtained by using adiabatic subtraction scheme. We therefore conclude the counterintuitive behaviors of the current in the infrared (IR) regime such as IR hyperconductivity and negative current are not artifacts of the renormalization scheme, but are real IR effects of the spacetime.
Quantum nonthermal effect of the Vaidya-Bonner-de Sitter black hole
NASA Astrophysics Data System (ADS)
Pan, Wei-Zhen; Yang, Xue-Jun; Yu, Guo-Xiang
2014-02-01
Using the Hamilton-Jacobi equation of a scalar particle in the curve space-time and a correct-dimension new tortoise coordinate transformation, the quantum nonthermal radiation of the Vaidya-Bonner-de Sitter black hole is investigated. The energy condition for the occurrence of the Starobinsky-Unruh process is obtained. The event horizon surface gravity and the Hawking temperature on the event horizon are also given.
Quantum Radiation of a Non-stationary Kerr Newman Black Hole in de Sitter Space Time
NASA Astrophysics Data System (ADS)
Jiang, Qing-Quan; Yang, Shu-Zheng
2006-12-01
Hawking radiation of Klein-Gordon and Dirac particles in a non-stationary Kerr-Newman-de-Sitter black hole is studied by introducing a new tortoise coordinate transformation. The result shows that the Fermi-Dirac radiant spectrum displays a new term that represents the interaction between the spin of spinor particles and the rotation of black holes, which is absent in the Bose-Einstein distribution of Klein-Gordon particles.
All gaugings and stable de Sitter in D = 7 half-maximal supergravity
NASA Astrophysics Data System (ADS)
Dibitetto, Giuseppe; Fernández-Melgarejo, Jose J.; Marqués, Diego
2015-11-01
We study the general formulation of gauged supergravity in seven dimensions with sixteen supercharges keeping duality covariance by means of the embedding tensor formalism. We first classify all inequivalent duality orbits of consistent deformations. Secondly, we analyse the complete set of critical points in a systematic way. Interestingly, we find the first examples of stable de Sitter solutions within a theory with such a large amount of supersymmetry.
Thermodynamics of the Schwarzschild-de Sitter black hole: Thermal stability of the Nariai black hole
Myung, Yun Soo
2008-05-15
We study the thermodynamics of the Schwarzschild-de Sitter black hole in five dimensions by introducing two temperatures based on the standard and Bousso-Hawking normalizations. We use the first-law of thermodynamics to derive thermodynamic quantities. The two temperatures indicate that the Nariai black hole is thermodynamically unstable. However, it seems that black hole thermodynamics favors the standard normalization and does not favor the Bousso-Hawking normalization.
2.5D complex resistivity modeling and inversion using unstructured grids
NASA Astrophysics Data System (ADS)
Xu, Kaijun; Sun, Jie
2016-04-01
The characteristic of complex resistivity on rock and ore has been recognized by people for a long time. Generally we have used the Cole-Cole Model(CCM) to describe complex resistivity. It has been proved that the electrical anomaly of geologic body can be quantitative estimated by CCM parameters such as direct resistivity(ρ0), chargeability(m), time constant(τ) and frequency dependence(c). Thus it is very important to obtain the complex parameters of geologic body. It is difficult to approximate complex structures and terrain using traditional rectangular grid. In order to enhance the numerical accuracy and rationality of modeling and inversion, we use an adaptive finite-element algorithm for forward modeling of the frequency-domain 2.5D complex resistivity and implement the conjugate gradient algorithm in the inversion of 2.5D complex resistivity. An adaptive finite element method is applied for solving the 2.5D complex resistivity forward modeling of horizontal electric dipole source. First of all, the CCM is introduced into the Maxwell's equations to calculate the complex resistivity electromagnetic fields. Next, the pseudo delta function is used to distribute electric dipole source. Then the electromagnetic fields can be expressed in terms of the primary fields caused by layered structure and the secondary fields caused by inhomogeneities anomalous conductivity. At last, we calculated the electromagnetic fields response of complex geoelectric structures such as anticline, syncline, fault. The modeling results show that adaptive finite-element methods can automatically improve mesh generation and simulate complex geoelectric models using unstructured grids. The 2.5D complex resistivity invertion is implemented based the conjugate gradient algorithm.The conjugate gradient algorithm doesn't need to compute the sensitivity matrix but directly computes the sensitivity matrix or its transpose multiplying vector. In addition, the inversion target zones are
Niu, Xiaofeng; Yang, Yongyi; King, Michael A
2012-09-01
Temporal regularization plays a critical role in cardiac gated dynamic SPECT reconstruction, of which the goal is to obtain an image sequence from a single acquisition which simultaneously shows both cardiac motion and tracer distribution change over the course of imaging (termed 5D). In our recent work, we explored two different approaches for temporal regularization of the dynamic activities in gated dynamic reconstruction without the use of fast camera rotation: one is the dynamic EM (dEM) approach which is imposed on the temporal trend of the time activity of each voxel, and the other is a B-spline modeling approach in which the time activity is regulated by a set of B-spline basis functions. In this work, we extend the B-spline approach to fully 5D reconstruction and conduct a thorough quantitative comparison with the dEM approach. In the evaluation of the reconstruction results, we apply a number of quantitative measures on two major aspects of the reconstructed dynamic images: (1) the accuracy of the reconstructed activity distribution in the myocardium and (2) the ability of the reconstructed dynamic activities to differentiate perfusion defects from normal myocardial wall uptake. These measures include the mean square error (MSE), bias-variance analysis, accuracy of time-activity curves (TAC), contrast-to-noise ratio of a defect, composite kinetic map of the left ventricle wall and perfusion defect detectability with channelized Hotelling observer. In experiments, we simulated cardiac gated imaging with the NURBS-based cardiac-torso phantom and Tc99m-Teboroxime as the imaging agent, where acquisition with the equivalent of only three full camera rotations was used during the imaging period. The results show that both dEM and B-spline 5D could achieve similar overall accuracy in the myocardium in terms of MSE. However, compared to dEM 5D, the B-spline approach could achieve a more accurate reconstruction of the voxel TACs; in particular, B-spline 5D could
Global Results for Linear Waves on Expanding Kerr and Schwarzschild de Sitter Cosmologies
NASA Astrophysics Data System (ADS)
Schlue, Volker
2015-03-01
In this global study of solutions to the linear wave equation on Schwarzschild de Sitter spacetimes we attend to the cosmological region of spacetime which is bounded in the past by cosmological horizons and to the future by a spacelike hypersurface at infinity. We prove an energy estimate capturing the expansion of that region, which combined with earlier results for the static region, yields a global boundedness result for linear waves. It asserts that a general finite energy solution to the global initial value problem has a limit on the future boundary at infinity that can be viewed as a function on the standard cylinder with finite energy, and that, moreover, any decay along the cosmological horizon is inherited along the future boundary. In particular, we exhibit an explicit nonvanishing quantity on the future boundary of the spacetime consistent with our expectations for the nonlinear stability problem. Our results apply to a large class of expanding cosmologies near the Schwarzschild de Sitter geometry, in particular subextremal Kerr de Sitter spacetimes.
Equivalence between Euclidean and in-in formalisms in de Sitter QFT
Higuchi, Atsushi; Marolf, Donald; Morrison, Ian A.
2011-04-15
We study the relation between two sets of correlators in interacting quantum field theory on de Sitter space. The first are correlators computed using in-in perturbation theory in the expanding cosmological patch of de Sitter space (also known as the conformal patch, or the Poincare patch), and for which the free propagators are taken to be those of the free Euclidean vacuum. The second are correlators obtained by analytic continuation from Euclidean de Sitter; i.e., they are correlators in the fully interacting Hartle-Hawking state. We give an analytic argument that these correlators coincide for interacting massive scalar fields with any m{sup 2}>0. We also verify this result via direct calculation in simple examples. The correspondence holds diagram by diagram, and at any finite value of an appropriate Pauli-Villars regulator mass M. Along the way, we note interesting connections between various prescriptions for perturbation theory in general static spacetimes with bifurcate Killing horizons.
Huygens' principle for the Klein-Gordon equation in the de Sitter spacetime
Yagdjian, Karen
2013-09-15
In this article we prove that the Klein-Gordon equation in the de Sitter spacetime obeys the Huygens' principle only if the physical mass m of the scalar field and the dimension n⩾ 2 of the spatial variable are tied by the equation m{sup 2}= (n{sup 2}−1)/4. Moreover, we define the incomplete Huygens' principle, which is the Huygens' principle restricted to the vanishing second initial datum, and then reveals that the massless scalar field in the de Sitter spacetime obeys the incomplete Huygens' principle and does not obey the Huygens' principle, for the dimensions n= 1, 3, only. Thus, in the de Sitter spacetime the existence of two different scalar fields (in fact, with m= 0 and m{sup 2}= (n{sup 2}−1)/4), which obey incomplete Huygens' principle, is equivalent to the condition n= 3, the spatial dimension of the physical world. In fact, Paul Ehrenfest in 1917 addressed the question: “Why has our space just three dimensions?”. For n= 3 these two values of the mass are the endpoints of the so-called in quantum field theory the Higuchi bound. The value m{sup 2}= (n{sup 2}−1)/4 of the physical mass allows us also to obtain complete asymptotic expansion of the solution for the large time.
Dynamics and quantum entanglement of two-level atoms in de Sitter spacetime
Tian, Zehua; Jing, Jiliang
2014-11-15
In the framework of open quantum systems, we study the internal dynamics of both freely falling and static two-level atoms interacting with quantized conformally coupled massless scalar field in de Sitter spacetime. We find that the atomic transition rates depend on both the nature of de Sitter spacetime and the motion of atoms, interestingly the steady states for both cases are always driven to being purely thermal, regardless of the atomic initial states. This thermalization phenomenon is structurally similar to what happens to an elementary quantum system immersed in a thermal field, and thus reveals the thermal nature of de Sitter spacetime. Besides, we find that the thermal baths will drive the entanglement shared by the freely falling atom (the static atom) and its auxiliary partner, a same two-level atom which is isolated from external fields, to being sudden death, and the proper time for the entanglement to be extinguished is computed. We also analyze that such thermalization and disentanglement phenomena, in principle, could be understood from the perspective of table-top simulation experiment.
Geometric phase of two-level atoms and thermal nature of de Sitter spacetime
NASA Astrophysics Data System (ADS)
Tian, Zehua; Jing, Jiliang
2013-04-01
In the framework of open quantum systems, we study the geometric phase acquired by freely falling and static two-level atoms interacting with quantized conformally coupled massless scalar fields in de Sitter-invariant vacuum. We find that, for the freely falling atom, the geometric phase gets a correction resulting from a thermal bath with the Gibbons-Hawking temperature, thus it clearly reveals the intrinsic thermal nature of de Sitter spacetime from a different physical context. For the static atom, there is a correction to the geometric phase coming from both the intrinsic thermal nature of de Sitter spacetime and the Unruh effect associated with the proper acceleration of the atom. Furthermore, in a gedanken experiment, we estimate the magnitude of the correction to the geometric phase as opposed to that in a flat spacetime. We find that the correction for the freely falling atom is too tiny to be measured, and that for the static atom achieves an observable magnitude only when the atom almost locates at the horizon.
Waveform tomography in 2.5-D to appropriately handle 3-D geometry
NASA Astrophysics Data System (ADS)
Smithyman, B.; Clowes, R. M.
2011-12-01
In order to improve the tractability of waveform tomography when applied to field data acquired along a crooked-line, we implement 2.5-D forward modeling and inversion. Waveform tomography combines conventional velocity-model building (i.e. tomography) with full-waveform inversion to reconstruct an image of subsurface acoustic velocity. For reasons of computational efficiency, it is desirable to use 2-D full-waveform inversion when processing data acquired with 2-D seismic survey geometry. However, crooked-line acquisition results in a cross-line component of the source-receiver offset that cannot be accounted for by 2-D forward modeling. If the cross-line geometry components are significant, full-waveform inversion may be intractable. To address the latter difficulty, we first apply 3-D traveltime tomography to generate a 2-D cross-sectional initial velocity model by taking a representative average slice through the 3-D model. Then this initial model from traveltime inversion is iteratively updated by 2.5-D full-waveform inversion using a frequency-domain viscoacoustic implementation. The 2.5-D method generates waveform data by combining the solutions of multiple 2-D wave equation components. Each wavefield represents the solution of a modified wave equation in which the cross-line wavenumber takes a value between zero and ~ω/c. The results are combined by inverse Fourier transform in the cross-line coordinate. This produces a synthetic wavefield that is a solution to the 3-D viscoacoustic wave equation in a 2-D velocity model. Consequently, the 2.5-D synthetic wavefield better approximates seismic field data (including crooked-line geometry), when compared to a 2-D synthetic result. Cross-line source-receiver offsets can be accounted for by reconstructing the wavefield out-of-plane with respect to the source. The amplitude and phase of the wavefield are consistent with a 3-D solution in a model that is homogeneous in one direction. The 2-D model is ideally
Dingle and de Sitter Against the Metaphysicians, or Two Ways to Keep Modern Cosmology Physical
NASA Astrophysics Data System (ADS)
Gale, George
It would be hard to find two more radically different personalities than the irascible Herbert Dingle and the courtly Willem de Sitter. Yet, when it came to their philosophy of science, these two otherwise-so-different men were united against a common enemy, those they both called the "metaphysicians." Right from 1917, de Sitter attempted always to keep cosmology tightly bound to real observations made upon a real world. In Kosmos, written near the end of his life, he re-affirms most strongly his principle that "there is nothing an orthodox physicist abhors more than metaphysics." Dingle, for his part, accepts early on the positivist use of the verifiability principle to eliminate metaphysics from science, and continuously wields the principle as a weapon against those errant cosmologists who would sacrifice science for a sort of mysticism. Both men reject the strict and literal use of the term "universe," and for the same reasons: there is no observation, no verification, of statements containing that term. Both men reject the "cosmological principle" as Milne and others use it, on the grounds, as de Sitter puts it, that "we have . . . no means of communicating with other observers, situated on faraway stars." Eddington, although always closely associated with de Sitter personally, comes in for his own fine share of criticism. After de Sitter's death, Dingle carried on the battle alone, always on the bases that he and de Sitter had earlier established. The two peaks in Dingle's long struggle were the notorious 1937 controversy in the pages of Nature, a nasty dogfight which managed to involve almost every single important physicist in Britain; thirteen years later, the long war with the metaphysicians ended with the pyrrhic victory of Dingle's Royal Astronomical Society Presidential Address' invective against the latest and greatest metaphysical creation, Bondi's steady state universe theory. In the end, however, it would be a mistake to believe that the campaign
Relaxing constraints from lepton flavor violation in 5D flavorful theories
NASA Astrophysics Data System (ADS)
Agashe, Kaustubh
2009-12-01
We propose new mechanisms for ameliorating the constraints on the Kaluza-Klein mass scale from charged lepton flavor violation in the framework of the standard model fields propagating in a warped extra dimension, especially in models accounting for neutrino data. These mechanisms utilize the extended five-dimensional (5D) electroweak gauge symmetry [SU(2)L×SU(2)R×U(1)X] which is already strongly motivated in order to satisfy electroweak precision tests in this framework. We show that new choices of representations for leptons under this symmetry (naturally) can allow small mixing angles for left-handed (LH) charged leptons and simultaneously large mixing angles for their SU(2)L partners, i.e., the LH neutrinos, with the neutrino data being accounted for by the latter mixings. Enhancement of charged lepton flavor violation by the large mixing angle observed in leptonic charged currents, which is present for the minimal choice of representations where the LH charged lepton and neutrino mixing angles are similar, can thus be avoided in these models. This idea might also be useful for suppressing the contributions to Bd,s mixing in this framework and in order to suppress flavor violation from exchange of superpartners (instead of from KK modes) in 5D “flavorful supersymmetry” models. Additionally, the less minimal representations can provide custodial protection for shifts in couplings of fermions to Z and, in turn, further suppress charged lepton flavor violation from tree-level Z exchange in the warped extra-dimensional scenario. As a result, ˜O(3)TeV KK mass scale can be simultaneously consistent with charged lepton flavor violation and neutrino data, even without any particular structure in the 5D flavor parameters in the framework of a warped extra dimension.
2.5D Modeling of TEM Data Applied to Hidrogeological Studies in PARANÁ Basin, Brazil
NASA Astrophysics Data System (ADS)
Bortolozo, C. A.; Porsani, J. L.; Santos, F. M.
2013-12-01
The transient electromagnetic method (TEM) is used all over the world and has shown great potential in hydrological, hazardous waste site characterization, mineral exploration, general geological mapping, and geophysical reconnaissance. However, the behavior of TEM fields are very complex and is not yet fully understood. Forward modeling is one of the most common and effective methods to understand the physical behavior and significance of the electromagnetics responses of a TEM sounding. Until now, there are a limited number of solutions for the 2D forward problem for TEM. More rare are the descriptions of a three-component response of a 3D source over 2D earth, which is the so-called 2.5D. The 2.5D approach is more realistic than the conventional 2D source previous used, once normally the source cannot be realistic represented for a 2D approximation (normally source are square loops). At present the 2.5D model represents the only way of interpreting TEM data in terms of a complex earth, due to the prohibitive amount of computer time and storage required for a full 3D model. In this work we developed a TEM modeling program for understanding the different responses and how the magnetic and electric fields, produced by loop sources at air-earth interface, behave in different geoelectrical distributions. The models used in the examples are proposed focusing hydrogeological studies, once the main objective of this work is for detecting different kinds of aquifers in Paraná sedimentary basin, in São Paulo State - Brazil. The program was developed in MATLAB, a widespread language very common in the scientific community.
Coupling Landform Evolution and Soil Pedogenesis - Initial Results From the SSSPAM5D Model
NASA Astrophysics Data System (ADS)
Willgoose, G. R.; Welivitiya, W. D. D. P.; Hancock, G. R.; Cohen, S.
2015-12-01
Evolution of soil on a dynamic landform is a crucial next step in landscape evolution modelling. Some attempts have been taken such as MILESD by Vanwalleghem et al. to develop a first model which is capable of simultaneously evolving both the soil profile and the landform. In previous work we have presented physically based models for soil pedogenesis, mARM and SSSPAM. In this study we present the results of coupling a landform evolution model with our SSSPAM5D soil pedogenesis model. In previous work the SSSPAM5D soil evolution model was used to identify trends of the soil profile evolution on a static landform. Two pedogenetic processes, namely (1) armouring due to erosion, and (2) physical and chemical weathering were used in those simulations to evolve the soil profile. By incorporating elevation changes (due to erosion and deposition) we have advanced the SSSPAM5D modelling framework into the realm of landscape evolution. Simulations have been run using elevation and soil grading data of the engineered landform (spoil heap) at the Ranger Uranium Mine, Northern Territory, Australia. The results obtained for the coupled landform-soil evolution simulations predict the erosion of high slope areas, development of rudimentary channel networks in the landform and deposition of sediments in lowland areas, and qualitatively consistent with landform evolution models on their own. Examination of the soil profile characteristics revealed that hill crests are weathering dominated and tend to develop a thick soil layer. The steeper hillslopes at the edge of the landform are erosion dominated with shallow soils while the foot slopes are deposition dominated with thick soil layers. The simulation results of our coupled landform and soil evolution model provide qualitatively correct and timely characterization of the soil evolution on a dynamic landscape. Finally we will compare the characteristics of erosion and deposition predicted by the coupled landform-soil SSSPAM
Inequalities in health status among rural residents: EQ-5D findings from household survey China
2014-01-01
Introduction This study analyzed inequalities in health status among different socioeconomic and demographic rural residents covered by the New Rural Cooperative Medical System in China. Methods A cross-sectional study was conducted in Lian Yungang City, China. A total of 337 respondents, who were selected by using a multistage stratified systematic random sampling method, completed the surveys. A questionnaire consisting of EQ-5D and demographic and socioeconomic information was adopted for data collection, and was administered by face-to-face interviews. Multiple regression models were employed to examine the differences in the Visual Analogue Scale (VAS) score and the EQ-5D dimensions. Results Compared with those with lower education attainment, the respondents with higher education levels tended to report a higher VAS score (β = 2.666, 95% CI: 0.978 to 6.310), and were less likely to suffer from pain/discomfort (OR = 3.968; 95% CI: 1.447 to 10.880). The singles were more likely than the married to report moderate or extreme problems in usual activities (OR = 4.583; 95% CI: 1.188 to 17.676) and mobility (OR = 10.666; 95% CI: 2.464 to 6.171). However, no statistically significant differences were identified between the respondents with different income levels in the VAS score and EQ-5D dimensions. Conclusions This study suggests that the singles and the people with lower education levels are high-risk groups for poorer health status in the Chinese rural population. The findings from this study warrant further investigation. PMID:24885378
Hamiltonian dynamics of 5D Kalb-Ramond theories with a compact extra dimension
NASA Astrophysics Data System (ADS)
Escalante, Alberto; López-Villanueva, A.
2015-03-01
A detailed Hamiltonian analysis for a 5D Kalb-Ramond, massive Kalb-Ramond and Stüeckelberg Kalb-Ramond theories with an extra compact dimension is performed. We develop a complete constraint program, then we quantize the theory by constructing the Dirac brackets. From the gauge transformations of the theories, we fix a particular gauge and we find pseudo-Goldstone bosons in Kalb-Ramond and Stüeckelberg Kalb-Ramond systems. Finally we discuss some remarks and prospects.
Cosmological expansion governed by a scalar field from a 5D vacuum
NASA Astrophysics Data System (ADS)
Bellini, Mauricio
2006-06-01
We consider a single field governed expansion of the universe from a five dimensional (5D) vacuum state. Under an appropiate change of variables the universe can be viewed in a effective manner as expanding in 4D with an effective equation of state which describes different epochs of its evolution. In the example here worked the universe firstly describes an inflationary phase, followed by a decelerated expansion. Thereafter, the universe is accelerated and describes a quintessential expansion to finally, in the future, be vacuum dominated.
A 5D noncompact and non Ricci flat Kaluza-Klein Cosmology
NASA Astrophysics Data System (ADS)
Darabi, F.
2009-03-01
A model universe is proposed in the framework of 5D noncompact Kaluza-Klein cosmology which is not Ricci flat. The 4D part as the Robertson-Walker metric is coupled to conventional perfect fluid, and its extra-dimensional part is coupled to a dark pressure through a scalar field. It is shown that neither early inflation nor current acceleration of the 4D universe would happen if the nonvacuum states of the scalar field would contribute to 4D cosmology.
The primordial explosion of a false white hole from a 5D vacuum
NASA Astrophysics Data System (ADS)
Madriz Aguilar, José Edgar; Moreno, Claudia; Bellini, Mauricio
2014-01-01
We explore the cosmological consequences of some possible big bang produced by a black-hole with mass M in a 5D extended SdS. Under these particular circumstances, the effective 4D metric obtained by the use of a constant foliation on the extra coordinate is comported as a false white hole (FWH), which evaporates for all unstable modes that have wavelengths bigger than the size of the FWH. Outside the white hole the repulsive gravitational field can be considered as weak, so that the dynamics for fluctuations of the inflaton field and the scalar perturbations of the metric can be linearized.
Quintessential inflation from a variable cosmological constant in a 5D vacuum
NASA Astrophysics Data System (ADS)
Membiela, Agustin; Bellini, Mauricio
2006-10-01
We explore an effective 4D cosmological model for the universe where the variable cosmological constant governs its evolution and the pressure remains negative along all the expansion. This model is introduced from a 5D vacuum state where the (space-like) extra coordinate is considered as noncompact. The expansion is produced by the inflaton field, which is considered as nonminimally coupled to gravity. We conclude from experimental data that the coupling of the inflaton with gravity should be weak, but variable in different epochs of the evolution of the universe.
4d/5d correspondence for the black hole potential and its critical points
NASA Astrophysics Data System (ADS)
Ceresole, Anna; Ferrara, Sergio; Marrani, Alessio
2007-11-01
We express the d=4, {\\cal N}=2 black hole effective potential for cubic holomorphic F functions and generic dyonic charges in terms of d = 5 real special geometry data. The 4d critical points are computed from the 5d ones, and their relation is elucidated. For symmetric spaces, we identify the BPS and non-BPS classes of attractors and the respective entropies. These always derive from simple interpolating formulae between four and five dimensions, depending on the volume modulus and on the 4d magnetic (or electric) charges.
EuroQol 5D Quality of Life in Meniere's Disorder Can Be Explained with Symptoms and Disabilities
ERIC Educational Resources Information Center
Levo, Hilla; Stephens, Dafydd; Poe, Dennis; Kentala, Erna; Rasku, Jyrki; Pyykko, Ilmari
2012-01-01
The purpose of this study was to determine the factors explaining changes in the generic quality of life among patients with Meniere's disorder (MD) and to evaluate the EuroQol 5D (EQ-5D) quality-of-life measures. A questionnaire focusing on symptoms and disabilities caused by MD was collected from 726 individuals. General health-related quality…
Review of studies mapping from quality of life or clinical measures to EQ-5D: an online database.
Dakin, Helen
2013-01-01
Systematic literature searches were conducted to identify studies that conducted statistical mapping to predict EQ-5D utilities or responses from any source instrument and reported the estimated algorithms in sufficient detail to allow other researchers to use them to predict EQ-5D in other studies. Ninety studies reporting 121 mapping algorithms met the inclusion criteria. The studies estimated EQ-5D utilities from 80 source instruments. All but two studies included direct utility mapping to predict EQ-5D utilities, while 20 studies (22%) conducted response mapping to predict responses to each EQ-5D domain. Seventy-two studies (80%) explored ordinary least squares regression and 16 (18%) used censored least absolute deviations (CLAD) models. The details of the studies identified are made available in an online database, which will be updated regularly to enable researchers to easily identify studies that can help them to estimate utilities for economic evaluation. PMID:24010873
Polymer encapsulated 2.5D sensor arrays as building blocks for creating smart objects
NASA Astrophysics Data System (ADS)
Lishchynska, Maryna; Moore, Liam; Rogoz, Daniel; Delaney, Kieran; Barrett, John
2010-03-01
One of the key challenges in developing effective and scalable technologies necessary to realise future pervasive systems and ubiquitous computing is implementing a methodology that genuinely integrates embedded sensing and processing capabilities with everyday materials and objects. Embedding intelligent systems into polymer materials and using such "smart blocks" for constructing smart objects is a promising way to achieve the above. This work provides new solutions to challenges of realising a functional system, comprising sensing, processing and actuating components, fully encapsulated in a block of polymer material. The paper also investigates the possibilities of connecting arrays of such smart blocks in 1.5-D and 2.5-D arrangements to form a modular smart object. Experimental and numerical studies were conducted to establish a level of degradation in mechanical properties and strength of the plastic materials embedded with inserts. In current work, a bare cubic system and the system in a capsule-like package were realised and tested. The results of a full physical characterisation of both individual smart blocks and smart block arrays are presented.
An Australian discrete choice experiment to value eq-5d health states.
Viney, Rosalie; Norman, Richard; Brazier, John; Cronin, Paula; King, Madeleine T; Ratcliffe, Julie; Street, Deborah
2014-06-01
Conventionally, generic quality-of-life health states, defined within multi-attribute utility instruments, have been valued using a Standard Gamble or a Time Trade-Off. Both are grounded in expected utility theory but impose strong assumptions about the form of the utility function. Preference elicitation tasks for both are complicated, limiting the number of health states that each respondent can value and, therefore, that can be valued overall. The usual approach has been to value a set of the possible health states and impute values for the remainder. Discrete Choice Experiments (DCEs) offer an attractive alternative, allowing investigation of more flexible specifications of the utility function and greater coverage of the response surface. We designed a DCE to obtain values for EQ-5D health states and implemented it in an Australia-representative online panel (n = 1,031). A range of specifications investigating non-linear preferences with respect to time and interactions between EQ-5D levels were estimated using a random-effects probit model. The results provide empirical support for a flexible utility function, including at least some two-factor interactions. We then constructed a preference index such that full health and death were valued at 1 and 0, respectively, to provide a DCE-based algorithm for Australian cost-utility analyses. PMID:23765787
Neutral currents probed by non-local transport in graphene with 5 d metal adatoms
NASA Astrophysics Data System (ADS)
Wang, Yilin; Cai, Xinghan; Xiao, Shudong; Bao, Wenzhong; Reutt-Robey, Janice; Fuhrer, Michael
Adsorption of adatoms on graphene has been theoretically proposed as an effective means to enhance spin-orbit coupling in graphene. Here we use the non-local measurement geometry to detect neutral currents (spin, valley, energy) through their Hall and inverse Hall effects. Single-layer graphene devices are probed in-situ in ultra-high vacuum while depositing 5 d heavy metal atoms (Ir, Au) at a temperature of 7 K. Surprisingly, we detect a non-local signal in pristine devices as well as metal-atom modified devices, with a consistent dependence of the signal on length and gate voltage for several devices. Changes in the non-local signal upon deposition of 5 d metal atoms appear governed by charge carrier mobility (reduced with increasing metal atom concentration) and are difficult to understand with spin Hall/inverse spin Hall effects alone due to increased spin-orbit coupling in graphene. We will discuss other possible origins of the non-local signal. This work was supported by the U.S. ONR MURI. MSF was supported by an ARC Laureate Fellowship.
2.5D heterogeneously integrated microsystem for high-density neural sensing applications.
Huang, Po-Tsang; Wu, Shang-Lin; Huang, Yu-Chieh; Chou, Lei-Chun; Huang, Teng-Chieh; Wang, Tang-Hsuan; Lin, Yu-Rou; Cheng, Chuan-An; Shen, Wen-Wei; Chuang, Ching-Te; Chen, Kuan-Neng; Chiou, Jin-Chern; Hwang, Wei; Tong, Ho-Ming
2014-12-01
Heterogeneously integrated and miniaturized neural sensing microsystems are crucial for brain function investigation. In this paper, a 2.5D heterogeneously integrated bio-sensing microsystem with μ-probes and embedded through-silicon-via (TSVs) is presented for high-density neural sensing applications. This microsystem is composed of μ-probes with embedded TSVs, 4 dies and a silicon interposer. For capturing 16-channel neural signals, a 24 × 24 μ-probe array with embedded TSVs is fabricated on a 5×5 mm(2) chip and bonded on the back side of the interposer. Thus, each channel contains 6 × 6 μ -probes with embedded TSVs. Additionally, the 4 dies are bonded on the front side of the interposer and designed for biopotential acquisition, feature extraction and classification via low-power analog front-end (AFE) circuits, area-power-efficient analog-to-digital converters (ADCs), configurable discrete wavelet transforms (DWTs), filters, and a MCU. An on-interposer bus ( μ-SPI) is designed for transferring data on the interposer. Finally, the successful in-vivo test demonstrated the proposed 2.5D heterogeneously integrated bio-sensing microsystem. The overall power of this microsystem is only 676.3 μW for 16-channel neural sensing. PMID:25576575
Spin relaxation and spin Hall transport in 5d transition-metal ultrathin films
NASA Astrophysics Data System (ADS)
Long, Nguyen H.; Mavropoulos, Phivos; Zimmermann, Bernd; Bauer, David S. G.; Blügel, Stefan; Mokrousov, Yuriy
2014-08-01
The spin relaxation induced by the Elliott-Yafet mechanism and the extrinsic spin Hall conductivity due to the skew scattering are investigated in 5d transition-metal ultrathin films with self-adatom impurities as scatterers. The values of the Elliott-Yafet parameter and of the spin-flip relaxation rate reveal a correlation with each other that is in agreement with the Elliott approximation. At 10-layer thickness, the spin-flip relaxation time in 5d transition-metal films is quantitatively reported about few hundred nanoseconds at atomic percent. This time scale is one and two orders of magnitude shorter than the values in Au and Cu thin films, respectively. The anisotropy effect of the Elliott-Yafet parameter and of the spin-flip relaxation rate with respect to the direction of the spin-quantization axis in relation to the crystallographic axes is also analyzed. We find that the anisotropy of the spin-flip relaxation rate is enhanced due to the Rashba surface states on the Fermi surface, reaching values as high as 97% in 10-layer Hf(0001) film or 71% in 10-layer W(110) film. Finally, the spin Hall conductivity as well as the spin Hall angle due to the skew scattering off self-adatom impurities are calculated using the Boltzmann approach. Our calculations employ a relativistic version of the first-principles full-potential Korringa-Kohn-Rostoker Green function method.
Thermodynamic analysis of universes with the initial and final de Sitter eras
NASA Astrophysics Data System (ADS)
Moradpour, H.; Sabet, M. T. Mohammadi; Ghasemi, A.
2015-08-01
Our aim is studying the thermodynamics of cosmological models including initial and final de Sitter eras. For this propose, bearing Cai-Kim temperature in mind, we investigate the thermodynamic properties of a dark energy (DE) candidate with variable energy density, and show that the state parameter of this dark energy candidate (ωD) should obey the ωD≠ - 1 constraint, whiles there is no interaction between the fluids filled the universe, and the universe is not in the de Sitter eras. Additionally, based on the thermal fluctuation theory, we study the possibility of inducing fluctuations to the entropy of the DE candidate due to a mutual interaction between the cosmos sectors. Therefore, we find a relation between the thermal fluctuations and the mutual interaction between the cosmos sectors, whiles the DE candidate has a varying energy density. Finally, bearing the coincidence problem in mind, we derive a constraint on the vacuum energy, and investigate its relation with the entropy evolution of the DE candidate. We also point to a model with initial and final de Sitter eras in which a gravitationally induced particle production process leads to change the expansion eras, whiles the corresponding pressure is considered as the cause of current accelerated phase. We study its thermodynamics, and show that such processes may also leave thermal fluctuations into the system. We also find an expression between the thermal fluctuations and the particle production rate. Finally, we use Hayward-Kodama temperature to get a relation for the horizon entropy in models including the gravitationally induced particle production process. Our study shows that the first law of thermodynamics is available on the apparent horizon whiles, the gravitationally induced particle production process, as the DE candidate, may add an additional term to the Bekenstein limit of the horizon. The relation between the validity of the second law of thermodynamics and the gravitationally particle
NASA Astrophysics Data System (ADS)
Mehdipour, S. Hamid
2013-06-01
We study some features of entropic force approach in the presence of a noncommutative Schwarzschild-deSitter black hole. In this setup, there exists a similarity between the small and large scales. There are two finite cut-off in very short and long distances wherein the force and energy graph stop abruptly at those scales. We find that the existence of a deSitter core around the origin, induced by noncommutativity, in addition to a standard deSitter background at large scale may lead to a violation of the equivalence principle. Finally in order to directly observe the finite cut-off at short-scale gravity, caused by noncommutativity quantum fluctuations, we derive an effective gravitational constant.
Komura, Kazumasa; Jeong, Seong Ho; Hinohara, Kunihiko; Qu, Fangfang; Wang, Xiaodong; Hiraki, Masayuki; Azuma, Haruhito; Lee, Gwo-Shu Mary; Kantoff, Philip W; Sweeney, Christopher J
2016-05-31
The androgen receptor (AR) plays an essential role in prostate cancer, and suppression of its signaling with androgen deprivation therapy (ADT) has been the mainstay of treatment for metastatic hormone-sensitive prostate cancer for more than 70 y. Chemotherapy has been reserved for metastatic castration-resistant prostate cancer (mCRPC). The Eastern Cooperative Oncology Group-led trial E3805: ChemoHormonal Therapy Versus Androgen Ablation Randomized Trial for Extensive Disease in Prostate Cancer (CHAARTED) showed that the addition of docetaxel to ADT prolonged overall survival compared with ADT alone in patients with metastatic hormone-sensitive prostate cancer. This finding suggests that there is an interaction between AR signaling activity and docetaxel sensitivity. Here we demonstrate that the prostate cancer cell lines LNCaP and LAPC4 display markedly different sensitivity to docetaxel with AR activation, and RNA-seq analysis of these cell lines identified KDM5D (lysine-specific demethylase 5D) encoded on the Y chromosome as a potential mediator of this sensitivity. Knocking down KDM5D expression in LNCaP leads to docetaxel resistance in the presence of dihydrotestosterone. KDM5D physically interacts with AR in the nucleus, and regulates its transcriptional activity by demethylating H3K4me3 active transcriptional marks. Attenuating KDM5D expression dysregulates AR signaling, resulting in docetaxel insensitivity. KDM5D deletion was also observed in the LNCaP-derived CRPC cell line 104R2, which displayed docetaxel insensitivity with AR activation, unlike parental LNCaP. Dataset analysis from the Oncomine database revealed significantly decreased KDM5D expression in CRPC and poorer prognosis with low KDM5D expression. Taking these data together, this work indicates that KDM5D modulates the AR axis and that this is associated with altered docetaxel sensitivity. PMID:27185910
Inhibition of light emission in a 2.5D photonic structure
Peretti, Romain; Seassal, Christian; Viktorovich, Pierre; Letartre, Xavier
2014-07-14
We analyse inhibition of emission in a 2.5D photonic structures made up of a photonic crystal (PhC) and Bragg mirrors using Finite Differences Time Domaine (FDTD) simulations. A comparison is made between an isolated PhC membrane and the same PhC suspended onto a Bragg mirror or sandwiched between 2 Bragg mirrors. Strong inhibition of the Purcell factor is observed in a broad spectral range, whatever the in-plane orientation and location of the emitting dipole. We analysed these results numerically and theoretically by simulating the experimentally observed lifetime of a collection of randomly distributed emitters, showing that their average emission rate is decreased by more than one decade, both for coupled or isolated emitters.
Simulations of the 2.5D inviscid primitive equations in a limited domain
NASA Astrophysics Data System (ADS)
Chen, Qingshan; Temam, Roger; Tribbia, Joseph J.
2008-12-01
The primitive equations (PEs) of the atmosphere and the oceans without viscosity are considered. These equations are not well-posed for any set of local boundary conditions. In space dimension 2.5 a set of nonlocal boundary conditions has been proposed in Chen et al. [Q. Chen, J. Laminie, A. Rousseau, R. Temam, J. Tribbia, A 2.5D Model for the equations of the ocean and the atmosphere, Anal. Appl. 5(3) (2007) 199-229]. The present article is aimed at testing the validity of these boundary conditions with physically relevant data. The issues tested are the well-posedness in the nonlinear case and the computational efficiency of the boundary conditions for limited area models [T.T. Warner, R.A. Peterson, R.E. Treadon, A tutorial on lateral boundary conditions as a basic and potentially serious limitation to regional numerical weather prediction, Bull. Amer. Meteor. Soc. 78(11) (1997) 2599-2617].
Instantons and the 5D U(1) gauge theory with extra adjoint
NASA Astrophysics Data System (ADS)
Poghossian, Rubik; Samsonyan, Marine
2009-07-01
In this paper, we compute the partition function of 5D supersymmetric U(1) gauge theory with extra adjoint matter in general Ω background. It is well known that such partition functions encode very rich topological information. We show in particular that unlike the case with no extra matter, the partition function with extra adjoint at some special values of the parameters directly reproduces the generating function for the Poincare polynomial of the moduli space of instantons. We compare our results with those recently obtained by Iqbal et al (Refined topological vertex, cylindric partitions and the U(1) adjoint theory, arXiv:0803.2260), who used the so-called refined topological vertex method.
Mixed Tracking and Projective Synchronization of 5D Hyperchaotic System Using Active Control
NASA Astrophysics Data System (ADS)
Ojo, Kayode; Ogunjo, Samuel T.; Williams, Oluwafemi
2013-08-01
This paper examines mixed tracking control and hy- brid synchronization of two identical 5-D hyperchaotic Lorenz systems via active control technique. The de- signed control functions for the mixed tracking enable each of the system state variables to stabilize at differ- ent chosen positions as well as control each state vari- ables of the system to track different desired smooth function of time. Also, the active control technique is used to design control functions which achieve projec- tive synchronization between the slave state variables and the master state variables. We also show that the coupling strength is inversely proportional to the syn- chronization time. Numerical simulations are carried out to validate the effectiveness of the analytical tech- nique.
Non-thermal leptogenesis in a simple 5D SO(10) GUT
Fukuyama, Takeshi; Okada, Nobuchika E-mail: okadan@ua.edu
2010-09-01
We discuss non-thermal leptogenesis in the scheme of 5D orbifold SO(10) GUT with the smooth hybrid inflation. With unambiguously determined Dirac Yukawa couplings and an assumption for the neutrino mixing matrix of the tri-bimaximal from, we analyze baryon asymmetry of the universe via non-thermal leptogenesis in two typical cases for the light neutrino mass spectrum, the normal and inverted hierarchical cases. The resultant baryon asymmetry is obtained as a function of the lightest mass eigenvalue of the light neutrinos, and we find that a suitable amount of baryon asymmetry of the universe can be produced in the normal hierarchical case, while in the inverted hierarchical case the baryon asymmetry is too small to be consistent with the observation.
Instant outdoor localization and SLAM initialization from 2.5D maps.
Arth, Clemens; Pirchheim, Christian; Ventura, Jonathan; Schmalstieg, Dieter; Lepetit, Vincent
2015-11-01
We present a method for large-scale geo-localization and global tracking of mobile devices in urban outdoor environments. In contrast to existing methods, we instantaneously initialize and globally register a SLAM map by localizing the first keyframe with respect to widely available untextured 2.5D maps. Given a single image frame and a coarse sensor pose prior, our localization method estimates the absolute camera orientation from straight line segments and the translation by aligning the city map model with a semantic segmentation of the image. We use the resulting 6DOF pose, together with information inferred from the city map model, to reliably initialize and extend a 3D SLAM map in a global coordinate system, applying a model-supported SLAM mapping approach. We show the robustness and accuracy of our localization approach on a challenging dataset, and demonstrate unconstrained global SLAM mapping and tracking of arbitrary camera motion on several sequences. PMID:26340773
Fermion creation in 5D space-time with a warped extra dimension
NASA Astrophysics Data System (ADS)
Chekireb, R.; Haouat, S.
2015-05-01
The phenomenon of fermion production in a 5D FRW space-time with a warped extra dimension is studied by considering the canonical method based on Bogoliubov transformation connecting the "in" with the "out" states. For an exactly solvable model, two sets of exact solution are expressed in terms of Bessel functions. Studying the semiclassical Hamilton-Jacobi equation, the "in" and "out" states are identified. The pair creation probability and the mean number of created particles are calculated from the Bogoliubov coefficients. It is shown that the particle creation probability and the number density of created particles depend on the ratio of the scale factors associated with the ordinary space {x} and the extra dimension. It is also shown that the contraction of the extra dimension induces particle creation like the ordinary space expansion.
Quintessential Inflation from 5d Warped Product Spaces on a Dynamical Foliation
NASA Astrophysics Data System (ADS)
da Silva, Lucio Fabio P.; Aguilar, José Edgar Madriz
Assuming the existence of a 5D purely kinetic scalar field on the class of warped product spaces we investigate the possibility of mimic both an inflationary and a quintessential scenarios on 4D hypersurfaces, by implementing a dynamical foliation on the fifth coordinate instead of a constant one. We obtain that an induced chaotic inflationary scenario with a geometrically induced scalar potential and an induced quasi-vacuum equation of state on 4D dynamical hypersurfaces is possible. While on a constant foliation, the universe can be considered as matter-dominated today, in a family of 4D dynamical hypersurfaces, the universe can be passing period of accelerated expansion with a deceleration parameter nearly -1. This effect of the dynamical foliation results negligible at the inflationary epoch allowing for a chaotic inflationary scenario and becomes considerable at the present epoch allowing a quintessential scenario.
Complex self-assembly of pyrimido[4,5-d]pyrimidine nucleoside supramolecular structures
NASA Astrophysics Data System (ADS)
Zhao, Hang; Guo, Xiurong; He, Shiliang; Zeng, Xin; Zhou, Xinglong; Zhang, Chaoliang; Hu, Jing; Wu, Xiaohua; Xing, Zhihua; Chu, Liangyin; He, Yang; Chen, Qianming
2014-01-01
Supramolecular self-assembly is not only one of the chemical roots of biological structure but is also drawing attention in different industrial fields. Here we study the mechanism of the formation of a complex flower-shaped supramolecular structure of pyrimido[4,5-d]pyrimidine nucleosides by dynamic light scattering, scanning electron microscopy, differential scanning calorimetry, nuclear magnetic resonance and X-ray analysis. Upon removing the hydroxyl group of sugars, different flower-shaped superstructures can be produced. These works demonstrate that complex self-assembly can indeed be attained through hierarchical non-covalent interactions of single molecules. Furthermore, chimerical structures built from molecular recognition by these monomers indicate their potential in other fields if combined with other chemical entities.
Conformally invariant spin-3/2 field equation in de Sitter space-time
NASA Astrophysics Data System (ADS)
Fatahi, N.
2015-09-01
In the previous paper (Behroozi et al., Phys Rev D 74:124014, 2006; Dehghani et al., Phys Rev D 77:064028, 2008), conformal invariance for massless tensor fields (scalar, vector and spin-2 fields) was studied and the solutions of their wave equations and two-point functions were obtained. In the present paper, conformally invariant wave equation for massless spinor field in de Sitter space-time has been obtained. For this propose, we use Dirac's six-cone formalism. The solutions of massless spin-1/2 and -3/2 equations, in the ambient space notation, have been calculated.
New tortoise coordinate transformation and Hawking's radiation in de Sitter space
NASA Astrophysics Data System (ADS)
Ibohal, N.; Ibungochouba, T.
2013-01-01
Hawking's radiation effect of Klein-Gordon equation, Dirac particles and Maxwell's electromagnetic fields in the non-stationary rotating de Sitter cosmological space-time is investigated by using a new method of generalized tortoise coordinate transformation. It is found that the new transformation produces constant additional terms in the expressions of the surface gravities and the Hawking's temperatures. If the constant terms are set to zero, then the surface gravities and Hawking's temperatures will be equal to those obtained from the old generalized tortoise coordinate transformations. This shows that the new transformations are more reasonable. The Fermionic spectrum of Dirac particles displays a new spin-rotation coupling effect.
Solution of Dirac equation in Reissner-Nordström de Sitter space
NASA Astrophysics Data System (ADS)
Lyu, Yan; Cui, Song
2009-02-01
The radial parts of the Dirac equation between the outer black hole horizon and the cosmological horizon are solved in Reissner-Nordström de Sitter (RNdS) space numerically. An accurate approximation, the polynomial approximation, is used to approximate the modified tortoise coordinate \\hat r_* , which leads to the inverse function r = r(\\hat r_* ) and the potential V(\\hat r_* ). The potential V(\\hat r_* ) is replaced by a collection of step functions in sequence. Then the solution of the wave equation as well as the reflection and transmission coefficients is computed by a quantum mechanical method.
Spinor Field at the Phase Transition Point of Reissner-Nordström de Sitter Space
NASA Astrophysics Data System (ADS)
Lyu, Yan; Zhang, Li-Qing; Zheng, Wei; Pan, Qing-Chao
2010-08-01
The radial parts of Dirac equation between the outer black hole horizon and the cosmological horizon are solved in Reissner-Nordström de Sitter (RNdS) space when it is at the phase transition point. We use an accurate polynomial approximation to approximate the modified tortoise coordinate hat{r}_{*} in order to get the inverse function r=r(hat{r}_{*}) and the potential V(hat{r}_{*}). Then we use a quantum mechanical method to solve the wave equation numerically. We consider two cases, one is when the two horizons are lying close to each other, the other is when the two horizons are widely separated.
Real scalar field scattering in the nearly extremal Schwarzschild—de Sitter space
NASA Astrophysics Data System (ADS)
Guo, Guang-Hai
2010-11-01
Reasonable approximations are introduced to investigate the real scalar field scattering in the nearly extremal Schwarzschild—de Sitter (SdS) space. The approximations naturally lead to the invertible x(r) and the global replacement of the true potential by a Pöshl—Teller one. Meanwhile, the Schrödinger-like wave equation is transformed into a solvable form. Our numerical solutions to the wave equation show that the wave is characteristically similar to the harmonic under the tortoise coordinate x, while the wave piles up near the two horizons and the wavelength tends to its maximum as the potential approaches to the peak under the radial coordinate r.
Hawking radiation of a Reissner-Nordström-de Sitter black hole
NASA Astrophysics Data System (ADS)
Zhao, Ren; Zhang, Li-Chun; Li, Huai-Fan
2010-04-01
Generalizing the method proposed by Damour-Ruffini, we discuss Hawking radiation of a Reissner-Nordström-de Sitter (RNdS) black hole. Under the condition that total energy and charge are conserved, taking the reaction of the radiation of particles to the spacetime into consideration and considering the interrelation between the event horizon and cosmological horizon, we investigate radiation spectrum of RNdS spacetime by a new Tortoise coordinate transformation. This radiation spectrum is no longer a purely thermal spectrum. It is related to the changes in the Bekenstein-Hawking entropy corresponding the event horizon and cosmological horizon. The result satisfies the unitary principle.
The algebra of supertraces for (2 + 1) super de Sitter gravity
Urrutia, L.F. ); Waelbroeck, H. ); Zertuche, F. )
1992-09-21
In this paper, the authors calculate the algebra of the observables for 2 + 1 super de Sitter gravity, for one genus of the spatial surface. The algebra turns out to be an infinite Lie algebra subject to nonlinear constraints. The authors solve the constraints explicitly in terms of five independent complex supertraces. These variables are the true degrees of freedom of the system and their quantized algebra generates a new structure which we refer to as a central extension of the quantum algebra SU(2)[sub q].
Production of scalar particles in electric field on de Sitter expanding universe
NASA Astrophysics Data System (ADS)
Băloi, Mihaela-Andreea
2014-08-01
The scalar particle production from vacuum in the presence of an electric field, on the de Sitter spacetime is studied. We use perturbation methods to define the transition amplitude. We obtain that the momentum is not conserved in this process. The probability density of pair production is computed by squaring the transition amplitude. Our graphical representations show that, the probability of scalar particle production was important only in the early stages of the universe, when Hubble's constant was very large in comparison with the mass of the particle. Also, we propose here a criterion for particle-antiparticle separation.
On Fayet-Iliopoulos Terms and de Sitter Vacua in Supergravity: Some Easy Pieces
Catino, Francesca; Villadoro, Giovanni; Zwirner, Fabio; /Padua U. /INFN, Padua
2012-03-27
We clarify a number of issues on Fayet-Iliopoulos (FI) terms in supergravity, keeping the formalism at a minimum and making use of explicit examples. We explain why, if the U(1) vector is massive everywhere in field space, FI terms are not genuine and can always be redefined away or introduced when they are not present. We formulate a simple anomaly-free model with a genuine FI term, a classically stable de Sitter (dS) vacuum and no global symmetries. We explore the relation between N = 2 and N = 1 FI terms by discussing N = 1 truncations of N = 2 models with classically stable dS vacua.
Indications of de Sitter spacetime from classical sequential growth dynamics of causal sets
Ahmed, Maqbool; Rideout, David
2010-04-15
A large class of the dynamical laws for causal sets described by a classical process of sequential growth yields a cyclic universe, whose cycles of expansion and contraction are punctuated by single 'origin elements' of the causal set. We present evidence that the effective dynamics of the immediate future of one of these origin elements, within the context of the sequential growth dynamics, yields an initial period of de Sitter-like exponential expansion, and argue that the resulting picture has many attractive features as a model of the early universe, with the potential to solve some of the standard model puzzles without any fine-tuning.
A barren landscape? - Metastable de Sitter vacua are nongeneric in string theory
Robbins, Daniel; Sethi, Savdeep
2005-02-15
We consider the generation of a nonperturbative superpotential in F-theory compactifications with flux. We derive a necessary condition for the generation of such a superpotential in F theory. For models with a single volume modulus, we show that the volume modulus is never stabilized by either Abelian instantons or gaugino condensation. We then comment on how our analysis extends to a larger class of compactifications. From our results, it appears that among large volume string compactifications, metastable de Sitter vacua (should any exist) are nongeneric.
Hawking radiation of Kerr-de Sitter black holes using Hamilton-Jacobi method
NASA Astrophysics Data System (ADS)
Ibungochouba Singh, T.; Ablu Meitei, I.; Yugindro Singh, K.
2013-05-01
Hawking radiation of Kerr-de Sitter black hole is investigated using Hamilton-Jacobi method. When the well-behaved Painleve coordinate system and Eddington coordinate are used, we get the correct result of Bekenstein-Hawking entropy before and after radiation but a direct computation will lead to a wrong result via Hamilton-Jacobi method. Our results show that the tunneling probability is related to the change of Bekenstein-Hawking entropy and the derived emission spectrum deviates from the pure thermal but it is consistent with underlying unitary theory.
The Stokes phenomenon and quantum tunneling for de Sitter radiation in nonstationary coordinates
NASA Astrophysics Data System (ADS)
Kim, Sang Pyo
2010-09-01
We study quantum tunneling for the de Sitter radiation in the planar coordinates and global coordinates, which are nonstationary coordinates and describe the expanding geometry. Using the phase-integral approximation for the Hamilton-Jacobi action in the complex plane of time, we obtain the particle-production rate in both coordinates and derive the additional sinusoidal factor depending on the dimensionality of spacetime and the quantum number for spherical harmonics in the global coordinates. This approach resolves the factor of two problem in the tunneling method.
Hawking radiation of Schwarzschild-de Sitter black hole by Hamilton-Jacobi method
NASA Astrophysics Data System (ADS)
Rahman, M. Atiqur; Hossain, M. Ilias
2012-05-01
We investigate the Hawking radiation of Schwarzschild-de Sitter (SdS) black hole by massive particles tunneling method. We consider the spacetime background to be dynamical, incorporate the self-gravitation effect of the emitted particles and show that the tunneling rate is related to the change of Bekenstein-Hawking entropy and the derived emission spectrum deviates from the pure thermal spectrum when energy and angular momentum are conserved. Our result is also in accordance with Parikh and Wilczek's opinion and gives a correction to the Hawking radiation of SdS black hole.
One loop graviton self-energy in a locally de Sitter background
tSAMIS, n.c. |; Woodard, R.P.
1996-02-01
The graviton tadpole has recently been computed at two loops in a locally de Sitter background. We apply intermediate results of this work to exhibit the graviton self-energy at one loop. This quantity is interesting both to check the accuracy of the first calculation and to understand the relaxation effect it reveals. In the former context we show that the self-energy obeys the appropriate Ward identity. We also show that its flat space limit agrees with the flat space result obtained by Capper in what should be the same gauge. 15 refs., 4 figs., 10 tabs.
Smeared hair and black holes in three-dimensional de Sitter spacetime
Park, Mu-In
2009-10-15
It is known that there is no three-dimensional analog of de Sitter black holes. I show that the analog does exist when non-Gaussian (i.e., ring-type) smearings of point matter hairs are considered. This provides a new way of constructing black hole solutions from hairs. I find that the obtained black hole solutions are quite different from the usual large black holes in that there are (i) large to small black hole transitions which may be considered as inverse Hawking-Page transitions and (ii) solitonlike (i.e., nonperturbative) behaviors. For Gaussian smearing, there is no black hole but a gravastar solution exists.
The algebra of supertraces for 2+1 super de Sitter gravity
NASA Technical Reports Server (NTRS)
Urrutia, L. F.; Waelbroeck, H.; Zertuche, F.
1993-01-01
The algebra of the observables for 2+1 super de Sitter gravity, for one genus of the spatial surface is calculated. The algebra turns out to be an infinite Lie algebra subject to non-linear constraints. The constraints are solved explicitly in terms of five independent complex supertraces. These variables are the true degrees of freedom of the system and their quantized algebra generates a new structure which is referred to as a 'central extension' of the quantum algebra SU(2)q.
Quantum scalar corrections to the gravitational potentials on de Sitter background
NASA Astrophysics Data System (ADS)
Park, Sohyun; Prokopec, Tomislav; Woodard, R. P.
2016-01-01
We employ the graviton self-energy induced by a massless, minimally coupled (MMC) scalar on de Sitter background to compute the quantum corrections to the gravitational potentials of a static point particle with a mass M . The Schwinger-Keldysh formalism is used to derive real and causal effective field equations. When evaluated at the one-loop order, the gravitational potentials exhibit a secular decrease in the observed gravitational coupling G. This can also be interpreted as a (time dependent) anti-screening of the mass M.
Electronic and mechanical properties of 5d transition metal mononitrides via first principles
Zhao Erjun; Wu Zhijian
2008-10-15
The electronic and mechanical properties of 5d transition metal mononitrides from LaN to AuN are systematically investigated by use of the density-functional theory. For each nitride, six structures are considered, i.e., rocksalt, zinc blende, CsCl, wurtzite, NiAs and WC structures. Among the considered structures, rocksalt structure is the most stable for LaN, HfN and AuN, WC structure for TaN, NiAs structure for WN, wurtzite structure for ReN, OsN, IrN and PtN. The most stable structure for each nitride is mechanically stable. The formation enthalpy increases from LaN to AuN. For LaN, HfN and TaN, the formation enthalpy is negative for all the considered structures, while from WN to AuN, except wurtzite structure in ReN, the formation enthalpy is positive. The calculated density of states shows that they are all metallic. ReN in NiAs structure has the largest bulk modulus, 418 GPa. The largest shear modulus 261 GPa is from TaN in WC structure. Trends are discussed. - Graphical abstract: Formation enthalpy per formula unit {delta}H (eV) for all the considered structures of 5d transition metal mononitrides MN (M=La-Au). It was shown that the formation enthalpy increases from LaN to AuN. The nitrides with negative values indicate that they can be synthesized experimentally at ambient conditions.
2.5D Finite/infinite Element Approach for Simulating Train-Induced Ground Vibrations
NASA Astrophysics Data System (ADS)
Yang, Y. B.; Hung, H. H.; Kao, J. C.
2010-05-01
The 2.5D finite/infinite element approach for simulating the ground vibrations by surface or underground moving trains will be briefly summarized in this paper. By assuming the soils to be uniform along the direction of the railway, only a two-dimensional profile of the soil perpendicular to the railway need be considered in the modeling. Besides the two in-plane degrees of freedom (DOFs) per node conventionally used for plane strain elements, an extra DOF is introduced to account for the out-of-plane wave transmission. The profile of the half-space is divided into a near field and a semi-infinite far field. The near field containing the train loads and irregular structures is simulated by the finite elements, while the far field covering the soils with infinite boundary by the infinite elements, by which due account is taken of the radiation effects for the moving loads. Enhanced by the automated mesh expansion procedure proposed previously by the writers, the far field impedances for all the lower frequencies are generated repetitively from the mesh created for the highest frequency considered. Finally, incorporated with a proposed load generation mechanism that takes the rail irregularity and dynamic properties of trains into account, an illustrative case study was performed. This paper investigates the vibration isolation effect of the elastic foundation that separates the concrete slab track from the underlying soil or tunnel structure. In addition, the advantage of the 2.5D approach was clearly demonstrated in that the three-dimensional wave propagation effect can be virtually captured using a two-dimensional finite/infinite element mesh. Compared with the conventional 3D approach, the present approach appears to be simple, efficient and generally accurate.
NASA Astrophysics Data System (ADS)
Zou, Li; Li, Fang-Yu; Li, Tao
2014-11-01
In this paper, we first deduce the Tolman-Oppenheimer-Volkoff (TOV) equations and Schwarzschild-de Sitter (SdS) constant-density interior solutions of perfect fluid spheres in hydrostatic equilibrium by the Einstein equations with a nonzero cosmological constant. The TOV equations and the spacetime properties of exact solutions inside uniform perfect fluid spheres with different spatial curvature and cosmological constants will be respectively analyzed in detail. Moreover, a brief comparison between the internal static solutions of the SdS type and the dynamical Einstein-Strauss-de Sitter (ESdS) vacuole spacetime is obtained.
Is the EQ-5D suitable for use in oncology? An overview of the literature and recent developments.
Schwenkglenks, Matthias; Matter-Walstra, Klazien
2016-04-01
The European Quality of Life-5 Dimensions (EQ-5D) questionnaire is widely used in oncology to generate quality of life weights (utilities). The typical purpose is to inform health economic evaluation studies. The EQ-5D is generally suitable for this purpose; it has shown a reasonable degree of reliability, content validity, construct validity and responsiveness in the majority of the available studies. In situations of doubt, combination with other quality-of-life instruments may be an option. The authors expect that the five-level version of the EQ-5D will gradually replace the three-level version, due to reduced ceiling effects and more appropriate responsiveness. Further research should address the benefits achievable through additional dimensions or patient-based valuation, and the validity of EQ-5D versions for proxy respondents. PMID:26808097
F5D-1 on ramp with Neil Armstrong preparing to fly a Dyna-Soar simulation
NASA Technical Reports Server (NTRS)
1962-01-01
The Douglas F5D-1 Skylancer being pre-flighted by the pilot while the crew chief prepares to pull the wheel chocks on the 'hot gun' ramp at Edwards Air Force Base, California. The aircraft was one of two prototype F5D-1s obtained by NASA Flight Research Center in 1961. The F5D-1 Skylancer (Bu. No. 142350) had a red and white paint pattern with a NASA identification number of 213 which later became NASA 708. The Douglas F5D-1 Skylancer was built by the Navy as an all-weather fighter interceptor that never made the jump to production. Four test aircraft were developed with the same basic airframe as the Douglas F4D Skyray. With increasing modifications the four aircraft were re-designated F5D-1s before their first flights. Future Astronaut Neil Armstrong was one of the NASA research pilots assigned to support duties for the Dyna-Soar program. In addition to working at the Boeing facility in Washington state, Armstrong also tested the Dyna-Soar launch abort profile using this F5D-1, which had a similar wing shape to the Dyna-Soar. The aircraft arrived at the Flight Research Center on June 15, 1961. After the Dyna-Soar program was cancelled in December 1963, this F5D-1 continued to be used, serving as a flying simulator for the M2-F2 and as a chase plane for lifting-body flights (providing the lifting-body pilot with an extra set of eyes to assist in emergencies and avert potential crashes) This F5D-1 left the Flight Research Center (later designated the Dryden Flight Research Center) on May 19, 1970, and was donated to the Neil A. Armstrong Museum in Wapakoneta, Ohio.
Hur, Hyewon; Kim, Young Han; Cho, Hee Young; Park, Yong Won; Won, Hye-Sung; Lee, Mi-Young; Yun, Bo Hyon; Lee, Kwang Hee; Kim, Sung Yoon; Yoo, Junsang
2015-01-01
Objective To evaluate the feasibility of five-dimensional Long Bone (5D LB), a new technique that automatically archives, reconstructs images, and measures lengths of fetal long bones, to assess whether the direction of volume sweep influences fetal long bone measurements in three-dimensional (3D) ultrasound and 5D LB, and to compare measurements of fetal long bone lengths obtained with 5D LB and those obtained with conventional two-dimensional (2D) and manual 3D techniques. Methods This prospective study included 39 singleton pregnancies at 26+0 to 32+0 weeks of gestation. Multiple pregnancies, fetuses with multiple congenital anomalies, and mothers with underlying medical diseases were excluded. Fetal long bones of the lower extremities-the femur, tibia, and fibula were measured by 2D and 3D ultrasound, and 5D LB, by an expert and non-expert examiner. First, we analyzed the 3D ultrasound and 5D LB data according to 2 different sweeping angles. We analyzed intra- and inter-observer variability and agreement between ultrasound techniques. Paired t-test, interclass correlation coefficient, and Bland-Altman plot and Passing-Bablok regression were used for statistical analysis. Results There was no statistical difference between long bone measurements analyzed according to 2 different volume-sweeping angles by 3D ultrasound and 5D LB. Intra- and inter-observer variability were not significantly different among all 3 ultrasound techniques. Comparing 2D ultrasound and 5D LB, the interclass correlation coefficient for femur, tibia, and fibula was 0.91, 0.92, and 0.89, respectively. Conclusion 5D LB is reproducible and comparable with conventional 2D and 3D ultrasound techniques for fetal long bone measurement. PMID:26217596
Recessional velocities and Hubble's law in Schwarzschild-de Sitter space
NASA Astrophysics Data System (ADS)
Klein, David; Collas, Peter
2010-03-01
We consider a spacetime with empty Schwarzschild-de Sitter exterior and Schwarzschild-de Sitter interior metric for a spherical fluid with constant density. The fluid interior may be taken to represent a galaxy supercluster, for which the proper distance from the center of the supercluster to the cosmological horizon has the same order of magnitude as the Hubble radius derived from Friedmann-Robertson-Walker cosmologies. The fluid interior and surrounding vacuum may also be considered as a model of the Local Group of galaxies in the far future. Particle motion is subject both to the attractive gravity exerted by the fluid and the repelling cosmological constant. Using global Fermi coordinates for the central observer within the fluid, the Fermi velocity, the astrometric velocity, the kinematic velocity, and the spectroscopic velocity, relative to the central (Fermi) observer, of a radially receding test particle are calculated and compared. We find that the Fermi relative velocity can exceed the speed of light in this model, but the presence of a positive cosmological constant causes recessional speeds of distant high energy particles to decrease rather than increase. We derive a version of Hubble’s law for this spacetime which might be applicable for the analysis of a receding mass within a great void adjacent to a supercluster, relatively isolated from gravitational sources other than the supercluster. We also compare some of our results to related behavior in Friedmann-Robertson-Walker cosmologies and consider implications to arguments regarding the expansion of space.
A note on the nonperturbative nature of the Schwinger effect in the expanding de Sitter space
NASA Astrophysics Data System (ADS)
Nicolaevici, Nistor
2015-02-01
We reconsider a recent perturbative calculation [M. A. Băloi, Mod. Phys. Lett. A29, 1450138 (2014)] of particle production in the expanding de Sitter space in an external electromagnetic field and apply it to the case of a constant uniform electric field in two dimensions. We show that perturbative number of created particles significantly differs from the existing nonperturbative result based on the Bogoliubov transformation method. We also point out that for a physically meaningful perturbative amplitude one should restrict to external potentials Aμ which in conformal coordinates vanish at infinite times. Potentials which do not respect this condition lead to gauge-dependent amplitudes, which also show close similarities with amplitudes in flat space in the unphysical case when the external potential suddenly vanishes. These problems are intimately linked with the finite upper limit of the conformal time in the de Sitter space and most probably a similar restriction should be imposed in perturbative calculations in FRW spacetimes with the same property.
Schwinger effect in 4D de Sitter space and constraints on magnetogenesis in the early universe
NASA Astrophysics Data System (ADS)
Kobayashi, Takeshi; Afshordi, Niayesh
2014-10-01
We investigate pair creation by an electric field in four-dimensional de Sitter space. The expectation value of the induced current is computed, using the method of adiabatic regularization. Under strong electric fields the behavior of the current is similar to that in flat space, while under weak electric fields the current becomes inversely proportional to the mass squared of the charged field. Thus we find that the de Sitter space obtains a large conductivity under weak electric fields in the presence of a charged field with a tiny mass. We then apply the results to constrain electromagnetic fields in the early universe. In particular, we study cosmological scenarios for generating large-scale magnetic fields during the inflationary era. Electric fields generated along with the magnetic fields can induce sufficiently large conductivity to terminate the phase of magnetogenesis. For inflationary magnetogenesis models with a modified Maxwell kinetic term, the generated magnetic fields cannot exceed 10-30 G on Mpc scales in the present epoch, when a charged field carrying an elementary charge with mass of order the Hubble scale or smaller exists in the Lagrangian. Similar constraints from the Schwinger effect apply for other magnetogenesis mechanisms.
Massive gravity on de Sitter and unique candidate for partially massless gravity
Rham, Claudia de; Renaux-Petel, Sébastien E-mail: srenaux@lpthe.jussieu.fr
2013-01-01
We derive the decoupling limit of Massive Gravity on de Sitter in an arbitrary number of space-time dimensions d. By embedding d-dimensional de Sitter into d+1-dimensional Minkowski, we extract the physical helicity-1 and helicity-0 polarizations of the graviton. The resulting decoupling theory is similar to that obtained around Minkowski. We take great care at exploring the partially massless limit and define the unique fully non-linear candidate theory that is free of the helicity-0 mode in the decoupling limit, and which therefore propagates only four degrees of freedom in four dimensions. In the latter situation, we show that a new Vainshtein mechanism is at work in the limit m{sup 2} → 2H{sup 2} which decouples the helicity-0 mode when the parameters are different from that of partially massless gravity. As a result, there is no discontinuity between massive gravity and its partially massless limit, just in the same way as there is no discontinuity in the massless limit of massive gravity. The usual bounds on the graviton mass could therefore equivalently well be interpreted as bounds on m{sup 2}−2H{sup 2}. When dealing with the exact partially massless parameters, on the other hand, the symmetry at m{sup 2} = 2H{sup 2} imposes a specific constraint on matter. As a result the helicity-0 mode decouples without even the need of any Vainshtein mechanism.
Hawking radiation of stationary and non-stationary Kerr-de Sitter black holes
NASA Astrophysics Data System (ADS)
Singh, T. Ibungochouba
2015-07-01
Hawking radiation of the stationary Kerr-de Sitter black hole is investigated using the relativistic Hamilton-Jacobi method. Meanwhile, extending this work to a non-stationary black hole using Dirac equations and generalized tortoise coordinate transformation, we derived the locations, the temperature of the thermal radiation as well as the maximum energy of the non-thermal radiation. It is found that the surface gravity and the Hawking temperature depend on both time and different angles. An extra coupling effect is obtained in the thermal radiation spectrum of Dirac particles which is absent from thermal radiation of scalar particles. Further, the chemical potential derived from the thermal radiation spectrum of scalar particle has been found to be equal to the highest energy of the negative energy state of the scalar particle in the non-thermal radiation for the Kerr-de Sitter black hole. It is also shown that for stationary black hole space time, these two different methods give the same Hawking radiation temperature.
Infrared dynamics of the massive ϕ4 theory on de Sitter space
NASA Astrophysics Data System (ADS)
Akhmedov, E. T.; Popov, F. K.; Slepukhin, V. M.
2013-07-01
We study massive real scalar ϕ4 theory in the expanding Poincare patch of de Sitter space. We calculate the leading two-loop infrared contribution to the two-point function in this theory. We do that for the massive fields both from the principal and complementary series. As can be expected at this order, light fields from the complementary series show stronger infrared effects than the heavy fields from the principal one. For the principal series, unlike the complementary one, we can derive the kinetic equation from the system of Dyson-Schwinger equation, which allows us to sum up the leading infrared contributions from all loops. We find two peculiar solutions of the kinetic equation. One of them describes the stationary Gibbons-Hawking-type distribution for the density per comoving volume. Another solution shows explosive (square root of the pole in finite proper time) growth of the particle number density per comoving volume. That signals the possibility of the destruction of the expanding Poincaré patch even by the very massive fields. We conclude with the consideration of the infrared divergences in global de Sitter space and in its contracting Poincaré patch.
Long-time asymptotics of a Bohmian scalar quantum field in de Sitter space-time
NASA Astrophysics Data System (ADS)
Tumulka, Roderich
2016-01-01
We consider a model quantum field theory with a scalar quantum field in de Sitter space-time in a Bohmian version with a field ontology, i.e., an actual field configuration \\varphi (x,t) guided by a wave function on the space of field configurations. We analyze the asymptotics at late times (t→ ∞ ) and provide reason to believe that for more or less any wave function and initial field configuration, every Fourier coefficient \\varphi _k(t) of the field is asymptotically of the form c_k√{1+k^2 exp (-2Ht)/H^2}, where the limiting coefficients c_k=\\varphi _k(∞) are independent of t and H is the Hubble constant quantifying the expansion rate of de Sitter space-time. In particular, every field mode \\varphi _k possesses a limit as t→ ∞ and thus "freezes." This result is relevant to the question whether Boltzmann brains form in the late universe according to this theory, and supports that they do not.
Oak, Sameer; Strnad, Greg; Bena, James; Farrow, Lutul D.; Parker, Richard D.; Jones, Morgan H.; Spindler, Kurt P.
2016-01-01
Objectives: The EQ-5D, PROMIS 10 Global Health, and VR-12 are generic patient reported outcome (PRO) questionnaires that assess and report patient general health and wellbeing. In choosing a PRO to track patient general health status, it is necessary to consider which measure will be the most responsive to change after treatment. To date, no studies exist comparing the responsiveness among the EQ-5D, PROMIS 10 Global Health, and VR-12. We sought to determine which of the generic PROs were most responsive internally and externally in the setting of knee arthroscopy. Methods: 50 patients undergoing knee arthroscopy were surveyed with a PRO questionnaire pre-operatively and at least 3 months post-operatively. PROs included the EQ-5D, EQ-5D visual analog scale, PROMIS 10 Global Health (PROMIS 10) Physical and Mental components, VR-12 Physical and Mental components, and the Knee injury and Osteoarthritis Outcome Score (KOOS) Pain scale. Internal responsiveness was evaluated by performing paired t-tests on the changes in measures and calculation of two measures of effect size: Cohen’s D and standardized response mean (SRM). External responsiveness was evaluated by calculating and comparing Pearson correlation measures between the disease specific reference KOOS Pain and the general PROs EQ-5D, PROMIS 10, and VR-12 changes. General PRO responsiveness measures were compared head to head with the cocor package in R software. Results: Patients were surveyed pre-operatively and a mean of 3.6 months post-operatively with 90% follow-up. For internal responsiveness, the EQ-5D, VR-12 Physical, and PROMIS 10 Physical scales showed a statistically significant improvement in score after treatment and effect size statistics with moderate change (Cohen’s D and SRM between 0.5-0.8). Assessing external responsiveness, the EQ-5D, VR-12 Physical, and PROMIS 10 Physical instruments showed the highest correlation with the disease specific reference measure, KOOS Pain (Table 1). For both
High-resolution infrared studies of perdeutero-spiropentane, C5D8
NASA Astrophysics Data System (ADS)
Erickson, B. A.; Ju, X.; Nibler, J. W.; Beaudry, C. M.; Blake, T. A.
2016-07-01
Perdeutero-spiropentane (C5D8) has been synthesized, and infrared and Raman spectra are reported for the first time. Wavenumber assignments are made for most of the fundamental vibrational states. Gas phase infrared spectra were recorded at a resolution (0.002 cm-1) sufficient to resolve individual rovibrational lines and show evidence of strong Coriolis and/or Fermi resonance interactions for most bands. However a detailed rovibrational analysis of the fundamental ν15 (b2) parallel band proved possible, and a fit of more than 1600 lines yielded a band origin of 1053.84465(10) cm-1 and ground state constants (in units of cm-1): B0 = 0.1120700(9), DJ = 1.51(3) × 10-8, DJK = 3.42(15) × 10-8. We note that the B0 value is significantly less than a value of Ba = 0.1140 cm-1 calculated using structural parameters from an earlier electron diffraction (ED) study, whereas one expects Ba to be lower than B0 because of thermal averaging over higher vibrational levels. A similar discrepancy was noted in an earlier study of C5H8 (Price et al., 2011). The structural and spectroscopic results are in good accord with values computed at the anharmonic level using the B3LYP density functional method with a cc-pVTZ basis set.
Order and anarchy hand in hand in 5D SO(10)
NASA Astrophysics Data System (ADS)
Vicino, D.
2015-07-01
A mechanism to generate flavour hierarchy via 5D wave-function localization is revisited in the context of SO(10) grand unified theory. In an extra-dimension compactified on an orbifold, fermions (living in the same 16 representation of SO(10)) result having exponential zero-modes profiles, localized around one of the brane. The breaking of SO(10) down to SU(5) × U(1)x provides the key parameter that distinguishes the profiles of the different SU(5) components inside the same 16 representation. Utilizing a suitable set of scalar fields, a predictive model for fermion masses and mixing is constructed and shown to be viable with the current data through a detailed numerical analysis. The scalar field content of the model is also suitable to solve the doublet-triplet splitting problem through the missing partner mechanism. All the Yukawa couplings in the model are anarchical and of order unity, while the hierarchies among different fermions result only from zero-mode profiles. The naturalness of Anarchical Yukawa couplings is studied, showing a preference for a normal ordered neutrino spectrum; predictions for various observables in the lepton sector are also derived.
Pressure-induced crossing of the core levels in 5 d metals
NASA Astrophysics Data System (ADS)
Tal, Alexey A.; Katsnelson, Mikhail I.; Ekholm, Marcus; Jönsson, H. Johan M.; Dubrovinsky, Leonid; Dubrovinskaia, Natalia; Abrikosov, Igor A.
2016-05-01
A pressure-induced interaction between core electrons, the core-level crossing (CLC) transition, has been observed in hcp Os at P ≈400 GPa [L. Dubrovinsky et al., Nature (London) 525, 226 (2015)], 10.1038/nature14681. By carrying out a systematic theoretical study for all metals of the 5 d series (Hf, Ta, W, Re, Os, Ir, Pt, Au) we have found that the CLC transition is a general effect for this series of metals. While in Pt it occurs at ≈1500 GPa , at a pressure substantially higher than in Os, in Ir it occurs already at 80 GPa. Moreover, we predict that in Re the CLC transition may take place already at ambient pressure. We explain the effect of the CLC and analyze the shift of the transition pressure across the series within the Thomas-Fermi model. In particular, we show that the effect has many common features with the atomic collapse in rare-earth elements.
Anisotropic magnetic interactions in 5d iridium oxides by many-body quantum chemistry calculations
NASA Astrophysics Data System (ADS)
Katukuri, Vamshi M.; Nishimoto, Satoshi; Yushankhai, Viktor; Rousochatzakis, Ioannis; Hozoi, Liviu; van den Brink, Jeroen
2014-03-01
Ir 5d5 oxides are being actively studied due to the realization of novel spin-orbit coupled jeff ~ 1/2 ground states. One remarkable feature in these compounds is the highly anisotropic magnetic interactions, orders of magnitude stronger than in 3d oxides. We address the nature of the anisotropic exchange in the 2D honeycomb (Na/Li)2IrO3 ((Na/Li)213) and square-lattice (Sr/Ba)2IrO4 ((Sr/Ba)213) iridates, by ab initio multireference configuration-interaction calculations on large embedded clusters. For Na213 we find that the Kitaev term is ferromagnetic and defines the dominant energy scale while the nearest-neighbor Heisenberg contribution is antiferromagnetic. Although Li213 is structurally similar, we predict quite different set of interaction parameters in Li213. We further analyze the magnetic order and the essential differences between these two materials by exact diagonalization and density-matrix renormalization-group calculations that additionally include 2nd and 3rd neighbor couplings. Sizable symmetric anisotropic interactions are also computed for Ba214. From the ab initio data, the relevant in-plane spin model for Ba214 turns out to be a Heisenberg-compass effective model. We finally discuss the Dzyaloshinskii-Moriya exchange in Sr214.
On Twisted N = 2 5D Super Yang-Mills Theory
NASA Astrophysics Data System (ADS)
Qiu, Jian; Zabzine, Maxim
2016-01-01
On a five-dimensional simply connected Sasaki-Einstein manifold, one can construct Yang-Mills theories coupled to matter with at least two supersymmetries. The partition function of these theories localises on the contact instantons, however, the contact instanton equations are not elliptic. It turns out that these equations can be embedded into the Haydys-Witten equations (which are elliptic) in the same way the 4D anti-self-dual instanton equations are embedded in the Vafa-Witten equations. We show that under some favourable circumstances, the latter equations will reduce to the former by proving some vanishing theorems. It was also known that the Haydys-Witten equations on product manifolds {M_5 = M_4 × R} arise in the context of twisting the 5D maximally supersymmetric Yang-Mills theory. In this paper, we present the construction of twisted N = 2 Yang-Mills theory on Sasaki-Einstein manifolds, and more generally on K-contact manifolds. The localisation locus of this new theory thus provides a covariant version of the Haydys-Witten equation.
Nature of the insulating ground state of the 5d postperovskite CaIrO3
Kim, Sun -Woo; Liu, Chen; Kim, Hyun -Jung; Lee, Jun -Ho; Yao, Yongxin; Ho, Kai -Ming; Cho, Jun -Hyung
2015-08-26
In this study, the insulating ground state of the 5d transition metal oxide CaIrO3 has been classified as a Mott-type insulator. Based on a systematic density functional theory (DFT) study with local, semilocal, and hybrid exchange-correlation functionals, we reveal that the Ir t2g states exhibit large splittings and one-dimensional electronic states along the c axis due to a tetragonal crystal field. Our hybrid DFT calculation adequately describes the antiferromagnetic (AFM) order along the c direction via a superexchange interaction between Ir4+ spins. Furthermore, the spin-orbit coupling (SOC) hybridizes the t2g states to open an insulating gap. These results indicate thatmore » CaIrO3 can be represented as a spin-orbit Slater insulator, driven by the interplay between a long-range AFM order and the SOC. Such a Slater mechanism for the gap formation is also demonstrated by the DFT + dynamical mean field theory calculation, where the metal-insulator transition and the paramagnetic to AFM phase transition are concomitant with each other.« less
The development of vector based 2.5D print methods for a painting machine
NASA Astrophysics Data System (ADS)
Parraman, Carinna
2013-02-01
Through recent trends in the application of digitally printed decorative finishes to products, CAD, 3D additive layer manufacturing and research in material perception, [1, 2] there is a growing interest in the accurate rendering of materials and tangible displays. Although current advances in colour management and inkjet printing has meant that users can take for granted high-quality colour and resolution in their printed images, digital methods for transferring a photographic coloured image from screen to paper is constrained by pixel count, file size, colorimetric conversion between colour spaces and the gamut limits of input and output devices. This paper considers new approaches to applying alternative colour palettes by using a vector-based approach through the application of paint mixtures, towards what could be described as a 2.5D printing method. The objective is to not apply an image to a textured surface, but where texture and colour are integral to the mark, that like a brush, delineates the contours in the image. The paper describes the difference between the way inks and paints are mixed and applied. When transcribing the fluid appearance of a brush stroke, there is a difference between a halftone printed mark and a painted mark. The issue of surface quality is significant to subjective qualities when studying the appearance of ink or paint on paper. The paper provides examples of a range of vector marks that are then transcribed into brush stokes by the painting machine.
I-IMAS: A 1.5D sensor for high-resolution scanning
NASA Astrophysics Data System (ADS)
Fant, A.; Gasiorek, P.; Turchetta, R.; Avset, B.; Bergamaschi, A.; Cavouras, D.; Evangelou, I.; French, M. J.; Galbiati, A.; Georgiou, H.; Hall, G.; Iles, G.; Jones, J.; Longo, R.; Manthos, N.; Metaxas, M. G.; Noy, M.; Ostby, J. M.; Psomadellis, F.; Royle, G. J.; Schulerud, H.; Speller, R. D.; van der Stelt, P. F.; Theodoridis, S.; Triantis, F.; Venanzi, C.
2007-04-01
We have developed a 1.5 D CMOS active pixel sensor to be used in conjunction with a scintillator for X-ray imaging. Within the Intelligent Imaging Sensors (I-ImaS) project, multiple sensors will be aligned to form a line-scanning system and its performance evaluated with respect to existing sensors in other digital radiography systems. Each sensor contains a 512×32 array of pixels and the electronics to convert the collected amount of charge to a digital output value. These include programmable gain amplifiers (PGAs) and analogue-to-digital converters (ADCs). The gain of the PGA can be switched between one or two, to increase the sensitivity for smaller collected charge; the ADC is a 14-bit successive approximation with a sampling rate of 1.25 MHz. The ASIC includes a programmable column fixed pattern noise mitigation circuit and a digitally controllable pixel reset mode block. Here we will describe the sensor design and the expected performance.
Spin-correlations and magnetic structure in an Fe monolayer on 5d transition metal surfaces.
Simon, E; Palotás, K; Ujfalussy, B; Deák, A; Stocks, G M; Szunyogh, L
2014-05-01
We present a detailed first principles study on the magnetic structure of an Fe monolayer on different surfaces of 5d transition metals. We use the spin-cluster expansion technique to obtain parameters of a spin model, and predict the possible magnetic ground state of the studied systems by employing the mean field approach and, in certain cases, by spin dynamics calculations. We point out that the number of shells considered for the isotropic exchange interactions plays a crucial role in the determination of the magnetic ground state. In the case of Ta substrate we demonstrate that the out-of-plane relaxation of the Fe monolayer causes a transition from ferromagnetic to antiferromagnetic ground state. We examine the relative magnitude of nearest neighbour Dzyaloshinskii-Moriya (D) and isotropic (J) exchange interactions in order to get insight into the nature of magnetic pattern formations. For the Fe/Os(0 0 0 1) system we calculate a very large D/J ratio, correspondingly, a spin spiral ground state. We find that, mainly through the leading isotropic exchange and Dzyaloshinskii-Moriya interactions, the inward layer relaxation substantially influences the magnetic ordering of the Fe monolayer. For the Fe/Re(0 0 0 1) system characterized by large antiferromagnetic interactions we also determine the chirality of the 120° Néel-type ground state. PMID:24759288
Synthesis of New Thiazolo[4,5-d]pyrimidines as Corticotropin Releasing Factor Modulators
Kuppast, Bhimanna; Spyridaki, Katerina; Lynch, Christophina; Hu, Yueshan; Liapakis, George; Davies, Gareth E.; Fahmy, Hesham
2015-01-01
Corticotropin-releasing factor (CRF) is a neurohormone that plays a crucial role in integrating the body’s overall response to stress. It appears necessary and sufficient for the organism to mount functional, physiological and endocrine responses to stressors. CRF is released in response to various triggers such as chronic stress. The role of CRF and its involvement in these neurological disorders suggest that new drugs that can target the CRF function or bind to its receptors may represent a new development of neuropsychiatric medicines to treat various stress-related disorders including depression, anxiety and addictive disorders. Based on pharmacophore of the CRF1 receptor antagonists, a new series of thiazolo[4,5-d] pyrimidines were synthesized as Corticotropin-releasing factor (CRF) receptor modulators and the prepared compounds carry groups shown to produce optimum binding affinity to CRF receptors. Twenty two compounds were evaluated for their CRF1 receptor binding affinity in HEK 293 cell lines and two compounds 5o and 5s showed approximately 25% binding affinity to CRF1 receptors. Selected compounds (5c and 5f) were also evaluated for their effect on expression of genes associated with depression and anxiety disorders such as CRF1, CREB, MAO-A, SERT, NPY, DatSLC6a3, and DBH and significant upregulation of CRF1 mRNA has been observed with compound 5c. PMID:25059547
NASA Astrophysics Data System (ADS)
Kolosov, Vladimir
2015-03-01
Unexpected transrotational microcrystals can be grown in thin 10-100 nm amorphous films. Crystals of different morphology (from nanowhiskers to spherulites, complex textures) and chemical nature (oxides, chalcogenides, metals and alloys) grown in thin films prepared by various methods are studied by transmission electron microscopy (TEM). We use primarily our TEM bend-contour method and SAED (HREM, AFM are also performed). The phenomenon resides in strong (up to 300 degrees/ μm) regular internal bending of crystal lattice planes in a growing crystal. It can be traced inside TEM in situ. Usual translation is complicated by slight regular rotation of the crystal unit cell (transrotation) most prominent at the mesoscale. Different geometries of transrotation of positive and negative curvature are revealed. Transrotational crystal resembles ideal single crystal enclosed in a curved space. It can be also considered similar to hypothetical endless 2.5 D analogy of MW nanotube/nano-onion halves. Transrotation is strongly increasing as the film gets thinner in the range 100-15 nm. Transrotations supplement dislocations and disclinations. New transrotational nanocrystalline model of amorphous state is proposed. Support of Ministry of Higher Education and Science is acknowledged.
Frequency-domain Green's functions for radar waves in heterogeneous 2.5D media
Ellefsen, K.J.; Croize, D.; Mazzella, A.T.; McKenna, J.R.
2009-01-01
Green's functions for radar waves propagating in heterogeneous 2.5D media might be calculated in the frequency domain using a hybrid method. The model is defined in the Cartesian coordinate system, and its electromagnetic properties might vary in the x- and z-directions, but not in the y-direction. Wave propagation in the x- and z-directions is simulated with the finite-difference method, and wave propagation in the y-direction is simulated with an analytic function. The absorbing boundaries on the finite-difference grid are perfectly matched layers that have been modified to make them compatible with the hybrid method. The accuracy of these numerical Greens functions is assessed by comparing them with independently calculated Green's functions. For a homogeneous model, the magnitude errors range from -4.16% through 0.44%, and the phase errors range from -0.06% through 4.86%. For a layered model, the magnitude errors range from -2.60% through 2.06%, and the phase errors range from -0.49% through 2.73%. These numerical Green's functions might be used for forward modeling and full waveform inversion. ?? 2009 Society of Exploration Geophysicists. All rights reserved.
Dimensional reduction of the 5D Kaluza-Klein geodesic deviation equation
NASA Astrophysics Data System (ADS)
Lacquaniti, V.; Montani, Giovanni; Vietri, F.
2010-02-01
In the work of Kerner et al. (Phys Rev D 63:027502, 2001) the problem of the geodesic deviation in a 5D Kaluza-Klein background is faced. The 4D space-time projection of the resulting equation coincides with the usual geodesic deviation equation in the presence of the Lorenz force, provided that the fifth component of the deviation vector satisfies an extra constraint which takes into account the q/ m conservation along the path. The analysis was performed setting as a constant the scalar field which appears in Kaluza-Klein model. Here we focus on the extension of such a work to the model where the presence of the scalar field is considered. Our result coincides with that of Kerner et al. when the minimal case {φ=1} is considered, while it shows some departures in the general case. The novelty due to the presence of {φ} is that the variation of the q/ m between the two geodesic lines is not conserved during the motion; an exact law for such a behaviour has been derived.
The real solution to scalar field equation in 5D black string space
NASA Astrophysics Data System (ADS)
Liu, Molin; Liu, Hongya; Luo, Feng; Xu, Lixin
2007-09-01
After the nontrivial quantum parameters Ω n and quantum potentials V n obtained in our previous research, the circumstance of a real scalar wave in the bulk is studied with the similar method of Brevik and Simonsen (Gen. Rel. Grav. 33:1839, 2001). The equation of a massless scalar field is solved numerically under the boundary conditions near the inner horizon r e and the outer horizon r c . Unlike the usual wave function Ψω l in 4D, quantum number n introduces a new functions Ψω l n , whose potentials are higher and wider with bigger n. Using the tangent approximation, a full boundary value problem about the Schr ödinger-like equation is solved. With a convenient replacement of the 5D continuous potential by square barrier, the reflection and transmission coefficients are obtained. If extra dimension does exist and is visible at the neighborhood of black holes, the unique wave function Ψω l n may say something to it.
2.5D forward modeling and inversion of frequency-domain airborne electromagnetic data
NASA Astrophysics Data System (ADS)
Li, Wen-Ben; Zeng, Zhao-Fa; Li, Jing; Chen, Xiong; Wang, Kun; Xia, Zhao
2016-03-01
Frequency-domain airborne electromagnetics is a proven geophysical exploration method. Presently, the interpretation is mainly based on resistivity—depth imaging and one-dimensional layered inversion; nevertheless, it is difficult to obtain satisfactory results for two- or three-dimensional complex earth structures using 1D methods. 3D forward modeling and inversion can be used but are hampered by computational limitations because of the large number of data. Thus, we developed a 2.5D frequency-domain airborne electromagnetic forward modeling and inversion algorithm. To eliminate the source singularities in the numerical simulations, we split the fields into primary and secondary fields. The primary fields are calculated using homogeneous or layered models with analytical solutions, and the secondary (scattered) fields are solved by the finite-element method. The linear system of equations is solved by using the large-scale sparse matrix parallel direct solver, which greatly improves the computational efficiency. The inversion algorithm was based on damping least-squares and singular value decomposition and combined the pseudo forward modeling and reciprocity principle to compute the Jacobian matrix. Synthetic and field data were used to test the effectiveness of the proposed method.
Correlation between the spin Hall angle and the structural phases of early 5d transition metals
Liu, Jun; Ohkubo, Tadakatsu; Mitani, Seiji; Hono, Kazuhiro; Hayashi, Masamitsu
2015-12-07
We have studied the relationship between the structure and the spin Hall angle of the early 5d transition metals in X/CoFeB/MgO (X = Hf, Ta, W, and Re) heterostructures. Spin Hall magnetoresistance (SMR) is used to characterize the spin Hall angle of the heavy metals. Transmission electron microscopy images show that all underlayers are amorphous-like when their thicknesses are small, however, crystalline phases emerge as the thickness is increased for certain elements. We find that the heavy metal layer thickness dependence of the SMR reflects these changes in structure. The largest spin Hall angle |θ{sub SH}| of Hf, Ta, W, and Re (∼0.11, 0.10, 0.23, and 0.07, respectively) is found when the dominant phase is amorphous-like. We find that the amorphous-like phase not only possesses large resistivity but also exhibits sizeable spin Hall conductivity, which both contribute to the emergence of the large spin Hall angle.
Neutrino masses via the Zee mechanism in the 5D split fermion model
Chang, We-Fu; Chen, I-Ting; Liou, Siao-Cing
2011-01-15
We study the original version of the Zee model, where both of the SU(2){sub L} Higgs doublets are allowed to couple to the leptons, in the framework of the split fermion model in M{sub 4}xS{sub 1}/Z{sub 2} space-time. The neutrino masses are generated through 1-loop diagrams without introducing the right-handed neutrinos. By assuming an order one anarchical complex 5D Yukawa couplings, all the effective 4D Yukawa couplings are determined by the wave function overlap between the split fermions and the bulk scalars in the fifth dimension. The predictability of the Yukawa couplings is in sharp contrast to the original Zee model in 4D where the Yukawa couplings are unknown free parameters. This setup exhibits a geometrical alternative to the lepton flavor symmetry. By giving four explicit sets of the split fermion locations, we demonstrate that it is possible to simultaneously fit the lepton masses and neutrino oscillation data by just a handful free parameters without much fine tuning. Moreover, we are able to make definite predictions for the mixing angle {theta}{sub 13}, the absolute neutrino masses, and the lepton flavor violation processes for each configuration.
Synthesis of new thiazolo[4,5-d]pyrimidines as Corticotropin releasing factor modulators.
Kuppast, Bhimanna; Spyridaki, Katerina; Lynch, Christophina; Hu, Yueshan; Liapakis, George; Davies, Gareth E; Fahmy, Hesham
2014-01-01
Corticotropin-releasing factor (CRF) is a neurohormone that plays a crucial role in integrating the body's overall response to stress. It appears necessary and sufficient for the organism to mount functional, physiological and endocrine responses to stressors. CRF is released in response to various triggers such as chronic stress. The role of CRF and its involvement in these neurological disorders suggest that new drugs that can target the CRF function or bind to its receptors may represent a new development of neuropsychiatric medicines to treat various stress-related disorders including depression, anxiety and addictive disorders. Based on pharmacophore of the CRF1 receptor antagonists, a new series of thiazolo[4,5-d] pyrimidines were synthesized as Corticotropin-releasing factor (CRF) receptor modulators and the prepared compounds carry groups shown to produce optimum binding affinity to CRF receptors. Twenty two compounds were evaluated for their CRF1 receptor binding affinity in HEK 293 cell lines and two compounds 5o and 5s showed approximately 25% binding affinity to CRF1 receptors. Selected compounds (5c and 5f) were also evaluated for their effect on expression of genes associated with depression and anxiety disorders such as CRF1, CREB1, MAO-A, SERT, NPY, DatSLC6a3, and DBH and significant upregulation of CRF1 mRNA has been observed with compound 5c. PMID:25059547
NASA Astrophysics Data System (ADS)
Braun, Andreas P.; Rummel, Markus; Sumitomo, Yoske; Valandro, Roberto
2015-12-01
In [1] a mechanism to fix the closed string moduli in a de Sitter minimum was proposed: a D-term potential generates a linear relation between the volumes of two rigid divisors which in turn produces at lower energies a race-track potential with de Sitter minima at exponentially large volume. In this paper, we systematically search for implementations of this mechanism among all toric Calabi-Yau hypersurfaces with h 1,1 ≤ 4 from the Kreuzer-Skarke list. For these, topological data can be computed explicitly allowing us to find the subset of three-folds which have two rigid toric divisors that do not intersect each other and that are orthogonal to h 1,1 - 2 independent four-cycles. These manifolds allow to find D7-brane configurations compatible with the de Sitter uplift mechanism and we find an abundance of consistent choices of D7-brane fluxes inducing D-terms leading to a de Sitter minimum. Finally, we work out a couple of models in detail, checking the global consistency conditions and computing the value of the potential at the minimum.
5D-QSAR for spirocyclic sigma1 receptor ligands by Quasar receptor surface modeling.
Oberdorf, Christoph; Schmidt, Thomas J; Wünsch, Bernhard
2010-07-01
Based on a contiguous and structurally as well as biologically diverse set of 87 sigma(1) ligands, a 5D-QSAR study was conducted in which a quasi-atomistic receptor surface modeling approach (program package Quasar) was applied. The superposition of the ligands was performed with the tool Pharmacophore Elucidation (MOE-package), which takes all conformations of the ligands into account. This procedure led to four pharmacophoric structural elements with aromatic, hydrophobic, cationic and H-bond acceptor properties. Using the aligned structures a 3D-model of the ligand binding site of the sigma(1) receptor was obtained, whose general features are in good agreement with previous assumptions on the receptor structure, but revealed some novel insights since it represents the receptor surface in more detail. Thus, e.g., our model indicates the presence of an H-bond acceptor moiety in the binding site as counterpart to the ligands' cationic ammonium center, rather than a negatively charged carboxylate group. The presented QSAR model is statistically valid and represents the biological data of all tested compounds, including a test set of 21 ligands not used in the modeling process, with very good to excellent accuracy [q(2) (training set, n=66; leave 1/3 out) = 0.84, p(2) (test set, n=21)=0.64]. Moreover, the binding affinities of 13 further spirocyclic sigma(1) ligands were predicted with reasonable accuracy (mean deviation in pK(i) approximately 0.8). Thus, in addition to novel insights into the requirements for binding of spirocyclic piperidines to the sigma(1) receptor, the presented model can be used successfully in the rational design of new sigma(1) ligands. PMID:20427100
Reducing NPR 7120.5D to Practice: Preparing for a Life-Cycle Review
NASA Technical Reports Server (NTRS)
Taylor, Randall L.
2008-01-01
In March 2007, NASA issued revised rules for space flight project management, NPR 7120.5D, 'NASA Space Flight Program and Project Management Requirements.' Central to the new rules was the construct of Key Decision Points, maturity gates that the project team must pass in order to continue development. In order that the KDP decision be fully informed, the NPR required, as entrance criteria for the gate, the generation and delivery of specified planning, technical, and cost/schedule documents (gate products) and a life-cycle review, the Preliminary Design Review. Building on JPL experience on the Prometheus and Juno projects, the team successfully organized for and conducted these reviews on an aggressive schedule. Key actions were taken to proactively interact with the SRB, produce high-quality gate products with stakeholder review, generate review presentation materials, and handle a myriad of supporting logistical functions. A review preparation team was established, including a Review Captain and leads for documentation, information systems, and logistics, and their roles, responsibilities and task assignments were identified. Aids were produced, including a detailed review preparation schedule and a comprehensive gate products production table. Institutional support was leveraged early and often. Implementation strategy reflected the needs of a nationally-distributed team, as well as applicable export control and IT security requirements. This paper gives a brief overview of the GRAIL mission and its project management challenges, provides a detailed description of project PMSR and PDR preparation and execution activities, including positive and negative lessons learned, and identifies recommendations for future NASA (and non-NASA) project teams.