Effect Of Spacetime Curvature Research Articles

General Relativistic Effects on the Ohmic Decay of Crustal Magnetic Fields in Neutron Stars

The ohmic decay of magnetic fields confined within the crust of neutron stars is considered by incorporating the effect of space-time curvature produced by the intense gravitational field of the star. It is shown that general relativistic effect reduces the magnetic field decay rate substaintially and specially at the late time of the evolution the decay rate decreases by several orders of magnitude when compared with the case without the relativistic effect.

Quantum inequalities on the energy density in static Robertson-Walker spacetimes

Quantum inequality restrictions on the stress-energy tensor for negative energy are developed for three and four-dimensional static spacetimes. We derive a general inequality in terms of a sum of mode functions which constrains the magnitude and duration of negative energy seen by an observer at rest in a static spacetime. This inequality is evaluated explicitly for a minimally coupled scalar field in three and four-dimensional static Robertson-Walker universes. In the limit of vanishing curvature, the flat spacetime inequalities are recovered. More generally, these inequalities contain the effects of spacetime curvature. In the limit of short sampling times, they take the flat space form plus subdominant curvature-dependent corrections.

The Effect of Light Bending and Redshift on Pulsar Beaming: The Case of Shorter Rotation Periods

AbstractAn estimate of the effect of light bending and redshift on pulsar beam characteristics has been made using a weak Kerr metric for the case of a 1.4 M⊙ neutron star with a radius in the range 6-10 km and rotation periods of 1.56 ms and 33 ms, respectively. Assuming that the pulsar emission has the form of a narrow conical beam directed away from the surface and is located within two stellar radii, the beam is found to be widened by a factor of ≤ 2 and to suffer a reduction in the intensity (flattening of the profile) by an order of magnitude or less. The effect is largest for the most rapidly rotating the neutron stars. For an emission region located beyond 20 km, the flattening is generally insignificant. The pulse profile is slightly asymmetrical due to dragging of the inertial frames. For millisecond periods, aberration tends to reverse the flattening effect of space-time curvature by narrowing the pulse and can completely overcome it for emission from a location beyond ≃30km. Although the pulse must slightly brighten up, a large redshift factor overcomes this effect to keep the pulse flattened for all neutron star radii considered here.

The effect of space-time curvature on Hilbert space

A new, unified basis for the study of gravitational effects in quantum and classical systems described by linear wave equations has been obtained by means of a covariant generalization of Berry's phase. The new formulation reveals aspects of the interaction of particles with weak gravitational fields hitherto thought to apply only to the stationary, nonrelativistic case. Though the emerging gauge structure is that of general relativity, weak gravitational fields behave as non-local vector fields. Their action on wave functions amounts, in first order, to a phase factor. Some effects predicted in the literature are re-calculated and extended to the fully relativistic regime. New effects are also predicted. The new approach affords a more precise description and a better understanding of particle interferometry as a tool to study gravitation.

Effects of spacetime curvature and rotation on arrival times of pulses from fast pulsars

view Abstract Citations (9) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Effects of Spacetime Curvature and Rotation on Arrival Times of Pulses from Fast Pulsars Kapoor, R. C. ; Datta, B. Abstract General relativistic effects due to spacetime curvature and rotation on the arrival times of pulsar signals are investigated using a rotationally perturbed spherical metric. It is found that for the millisecond pulsar PSR 1937+214, the advancement in arrival time (assuming the usual polar cap model for emission mechanism and a radius-to-frequency mapping) due to these effects is nontrivial. The results are compared with recent multifrequency timing measurements on PSR 1937+214, and the implications regarding emission region thickness and emission mechanism for fast pulsars are pointed out. Publication: The Astrophysical Journal Pub Date: December 1986 DOI: 10.1086/164806 Bibcode: 1986ApJ...311..680K Keywords: Pulsars; Pulse Rate; Relativistic Effects; Signal Analysis; Space-Time Functions; Drag; Polar Caps; Stellar Models; Stellar Rotation; Astrophysics; PULSARS; RELATIVITY full text sources ADS | data products SIMBAD (1)

Fast pulsars - Effects of spacetime curvature and rotation on the pulse characteristics

view Abstract Citations (10) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Fast pulsars : effects of spacetime curvature and rotation on the pulse characteristics. Kapoor, R. C. ; Datta, B. Abstract The effects of spacetime curvature and rotation on the pulse profile of fast pulsars are studied using a rotationally perturbed spherical metric and a representative choice of the equation of state for neutron star matter. Spacetime curvature is found to produce a divergence in the pulse width and a deamplification of the pulse intensity. Rotation is found to produce an asymmetry in the final pulse profile accompanied by a tilt of the pulse cone axis from its original direction of emission. The astrophysical implications of these results pertaining to the pulse characteristics of fast pulsars are discussed. Publication: The Astrophysical Journal Pub Date: October 1985 DOI: 10.1086/163540 Bibcode: 1985ApJ...297..413K Keywords: Equations Of State; Perturbation Theory; Pulsars; Relativity; Space-Time Functions; Neutron Stars; Red Shift; Stability; Astrophysics full text sources ADS | data products SIMBAD (1)

Gravitational instability and curvature effect at finite temperature

We investigate the gravitational instability which is indicated by the appearance of an imaginary mass proportional to the squared temperature. We show in the perturbative calculations that the time component of the graviton's self-energy Pi/sub 00,00/, which was calculated by Gross, Perry, and Yaffe, depends on the definitions of the graviton field, while Pi/sub 00,00/-Pi/sup ..mu../ /sub mu,00/ does not depend on them. However, the mass derived from it is found to differ from the one in the classical argument by a factor 3. The effect of space-time curvature on this instability is qualitatively studied.

Symmetry behavior in the Einstein universe: Effect of spacetime curvature and arbitrary field coupling

For the investigation of the effect of spacetime curvature and arbitrary field coupling on symmetry restoration, we have computed by zeta-function regularization the one-loop effective potential for a self-interacting scalar field arbitrarily coupled to a static Robertson-Walker universe. The classical contribution of curvature can restore broken symmetries for a wide range of parameters from conformal to near-minimal couplings whereas the quantum contribution is important only for a small range of values near the minimal coupling point. The symmetry behavior of the two extremes is found to be very different.

Gravitational effects upon cosmological phase transitions

The effects of spacetime curvature upon phase transitions in an expanding universe are investigated. We consider a Robertson-Walker model which is a radiation-dominated universe at early times and becomes de Sitter space at later times. In this universe the stability of a field theory containing a pair of interacting scalar fields is studied in first-order perturbation theory. It is noted that the crucial quantity in the stability analysis is $〈{\ensuremath{\varphi}}^{2}〉$, where $\ensuremath{\varphi}$ is a free scalar field. The behavior of $〈{\ensuremath{\varphi}}^{2}〉$ as a function of time is investigated, where both thermal and vacuum contributions are taken into account. It is shown that this behavior can be strongly affected by the coupling to the background gravitational field. Such coupling can cause $〈{\ensuremath{\varphi}}^{2}〉$ to decrease more slowly or even grow as the universe expands. This behavior can alter the evolution of the system and can result in either stabilization of an otherwise unstable field configuration or destabilization of an otherwise stable configuration.

Comments on the coherent-state representation of a scalar field in the early universe

Previous work on the coherent states of a cosmological scalar field is extended to illustrate the effect of spacetime curvature on the coherent-state parametrization. Coherent states for the "flat Kasner" ("Rindler wedge") cosmology are constructed as an example. It is shown that the coherent-state representation is invariant under a conformal transformation which does not alter the definition of positive frequency.

Effects of spacetime curvature on a cosmological first-order phase transition

It is shown that the spacetime curvature of the expanding universe may affect seriously the calculation on the first-order phase transition which might have taken place at the energy range of grand unification.

Effects of spacetime curvature on a cosmological first-order phase transition

Effects of spacetime curvature on a cosmological first-order phase transition

Neutron star electrodynamics in curved space

We calculate the fields surrounding and the power radiated by a slowly rotating neutron star with a frozen-in magnetic dipole field, tilted with respect to the rotation axis, including the effects of spacetime curvature. The general relativistic effects suppress the radiated power relative to flat space by factors up to 1/7 for magnetic dipole radiation and 1/50 for the associated electric quadrupole radiation. This suppression exceeds that which might be expected from a surface red shift alone.

Gyromagnetic Ratio of a Massive Body

It is well known that the gyromagnetic ratio (g factor) of a classical, slowly rotating body whose charge density is proportional to its mass density must be equal to unity. However, if the body is very massive, the spacetime curvature effects of general relativity become important and the result g = 1 is no longer valid. We calculate here the gyromagnetic ratio of a slowly rotating, massive shell with uniform charge density. When the shell is large compared with the Schwarzschild radius we have g = 1, but as the shell becomes more massive the g factor increases. In the limit as the shell approaches its Schwarzschild radius we obtain g approaching 2 (the same value as for an electron).