Search

We obtain static, asymptotically flat, multi-polytropic wormhole solutions in the framework of general relativity. We examine gravitational lensing in the presence of the wormhole and calculate the deflection angle for both weak and strong fields. We investigate microlensing in the weak field limit and obtain corresponding light curves for both galactic and extragalactic situations. We discuss the astrophysical motivation of considering the multi-polytropic equation of state that supports the wormhole geometry. Finally, we investigate the energy conditions. Key words: wormhole, gravitational lensing, energy condition, stability, multipolytropic. Dans le cadre de la relativite generale, nous obtenons des solutions trous de ver multi-polytropiques, asymptotiquement plates et statiques. Nous examinons l'effet de lentille gravitationnelle en presence du trou de ver et calculons l'angle de deflexion pour champ faible et champ fort. Nous analysons l'effet microlentille dans la limite du champ faible et obtenons les courbes de lumiere pour les cadres galactiques et extragalactiques. Nous discutons la motivation astrophysique de considerer l'equation d'etat multi-polytropique supportant la geometrie trou de ver. Finalement, nous regardons les conditions energetiques. Mots-cles: trou de ver, lentille gravitationnelle, condition energetique, stabilite, multi-polytropique., 1. Introduction In classical general relativity (GR), the Einstein field equations admit a simple and interesting class of static solutions describing tunnels in space-time connecting either two remote regions of [...]

There are a number of reasons to study wormholes with generic cosmological constant A. Recent observations indicate that the present accelerating expansion of the universe demands [LAMBDA] > 0. On the other hand, some extended theories of gravitation, such as supergravity and superstring theories, possess vacuum states with [LAMBDA] < 0. Even within the framework of general relativity, a negative cosmological constant permits black holes with horizons topologically different from the usual spherical ones. These solutions are convertible to wormhole solutions by adding some exotic matter. In this paper, the asymptotically flat wormhole solutions in a generic cosmological constant background are studied. By constructing a specific class of shape functions, a mass function, energy density, and pressure profile that support such a geometry are obtained. It is shown that for having such a geometry, the wormhole throat, [r.sub.0], the cosmological constant, [LAMBDA], and the equation of state parameter, [omega], should satisfy two specific conditions. The possibility of setting different values for the parameters of the model helps us to find exact solutions for the metric functions, mass functions, and energy-momentum profiles. At last, the volume integral quantifier, which provides useful information about the total amount of energy-condition violating matter, is discussed briefly. Key words: Lorentzian wormhole, de Sitter background, asymptotycally flat condition, volume integral quantifier, anti- de Sitter background. Il y a plusieurs raisons d'etudier les trous de ver avec une constante cosmologique generique [LAMBDA]. Des observations recentes indiquent que l'acceleration de l'Univers exige que [LAMBDA] > 0. D'un autre cote, certaines theories de la gravitation, comme la supergravite ou les theories de super-cordes ont des etats du vide avec [LAMBDA] < 0. Meme dans le cadre de la relativite generale, une constante cosmologique negative permet des trous noirs avec des horizons qui sont topologiquement differents de l'habituelle symetrie spherique. Ces solutions sont convertibles en solutions trous de ver par l'ajout de matiere exotique. Nous etudions ici les solutions trous de ver asymptotiquement plates sur un fond cosmologique generique constant. En construisant des fonctions de forme, nous obtenons une fonction de masse, une densite d'energie et des profils de pression qui supportent une telle geometrie. Nous montrons que pour avoir cette geometrie, le col du trou de ver [r.sub.0], la constante cosmologique [LAMBDA] et l'equation du parametre d'etat [omega] doivent satisfaire deux conditions specifiques. La possibilite d'ajuster differentes valeurs aux parametres du modele nous aide a trouver des solutions exactes pour les fonctions de metrique et de masse et pour les profils d'energie-impulsion. Finalement, nous discutons brievement du quantificateur de l'integrale de volume, qui fournit de l'information utile sur la quantite totale de matiere violant la condition sur l'energie. [Traduit par la Redaction] Mots-cles: trou de ver de Lorentz, fond de Sitter, conditions asymptotiquement plates, quantificateur de l'integrale de volume, fond anti de Sitter. PACS Nos.: 04.20.Jb, 98.80.Es., 1. Introduction In general relativity, geometrical bridges connecting two distant regions of a universe or even two different universes are in principle possible. Space-times containing such bridges appear as solutions [...]

Experimental and clinical investigations indicate that antibody production and Tvliclper 2 (TN2) cvtokinc pattern, cg; Irucrtcukinc - -I, 10 (JL.J, ILID) arc domin ant during pregnancy_ COflSCqllCIlI~"" The T-/iclpa 1 (THI) celts activities decrease in pregnancy. Thus the cell- mediated immunity is paniattv depressed. All these events help fetus as an allograft survives ill the mother's wems. III this research we: measured Tli cvtokincs in the sera of hcalthv prcgncl!lf and llOfl-preglJ{mr women (IL]. IL-I. intcrfron-gannna; IFN-y). Pregnant women '""1101"'(~d s(l,'lliftcaw decrease ill mean semm level of IL2 and IFN - Y. this means depression of cell- mediated immunity. This /illdillt; explains increased incidence oj some of the intmccllutvr injections ami survival 0/ the [ctus during pregnancy.