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1.
Quantum Inequality for Negative Energy Density States of Massive Dirac Field in Four-Dimensional Spacetime 下载免费PDF全文
Negative energy density and the quantum inequality are examined for the Dirac field. A proof is given of the quantum inequality for negative energy densities in the massive Dirac field produced by the superposition of two single particle electron states. 相似文献
2.
This paper investigates the quantum Dirac field in n+1-dimensional flat
spacetime and derives a lower bound in the form of quantum
inequality on the energy density averaged
against spacetime sampling functions. The state-independent quantum inequality
derived in the present paper is
similar to the temporal quantum energy inequality and
it is stronger for massive
field than for massless one. It also
presents the concrete results of the quantum inequality in 2 and
4-dimensional spacetimes. 相似文献
3.
Atomic population oscillations between two coupled Bose——Einstein condensates with time-dependent nonlinear interaction 下载免费PDF全文
The atomic population oscillations between two Bose--Einstein
condensates with time-dependent nonlinear interaction in a
double-well potential are studied. We first analyse the stabilities
of the system's steady-state solutions. And then in the perturbative
regime, the Melnikov chaotic oscillation of atomic population
imbalance is investigated and the Melnikov chaotic criterion is
obtained. When the system is out of the perturbative regime,
numerical calculations reveal that regulating the nonlinear parameter
can lead the system to step into chaos via period doubling
bifurcations. It is also numerically found that adjusting the
nonlinear parameter and asymmetric trap potential can result in the
running-phase macroscopic quantum self-trapping (MQST). In the
presence of a weak asymmetric trap potential, there exists the
parametric resonance in the system. 相似文献
4.
The one-loop vacuum polarization is calculated for scalar electrodynamics in a flat space-time with the topology S1×R3. The effect of vacuum polarization upon photon propagation is considered. It is found that photon propagation becomes anisotropic with some photon modes acquiring a positive topological mass and thus travelling at a subluminal speed. 相似文献
5.
Assuming that the effects of trans-Planckian physics are encoded in the choice of initial conditions, mode by mode, for vacuum states at the time when its wavelength becomes equal to the scale of new physics (Planck's scale for example), we calculate the spectrum of energy densities of total relic gravitational waves from de Sitter inflation to the matter dominated universe. Our results show that the spectrum acquires corrections due to the consideration of trans-Planckian physics and these corrections depend sensitively on the vacuum state that was actually realized at the beginning of the inflation. 相似文献
6.
We analyze the attractor behaviour of the inflation field in braneworld scenarios using the Hamilton-Jacobi formalism, where the Friedmann equation has the form of H2 = ρ + ε(2ρ0ρ)~(1/2) or H2 = ρ + ερ2/2σ , with ε = ±1. We find that in all models the linear homogeneous perturbation can decay exponentially as the scalar field rolls down its potential. However, in the case of a -ρ2 correction to the standard cosmology with ρ σ , the existence of an attractor solution requires (σρ)/φ2 1. Our results show that the perturbation decays more quickly in models with positive-energy correction than in the standard cosmology, which is opposite to the case of negative-energy correction. Thus, the positive-energy modification rather than the negative one can assist the inflation and widen the range of initial conditions. 相似文献
7.
Vacuum Polarization of Twisted Scalars in a Non—simply Connected Space—time and Its Effects 下载免费PDF全文
The vacuum polarization due to twisted scalar fields is investigated in a non-simply connected space-time,It is found that some photon modes acpuire an imaginary topological mass,thus travelling at a superluminal speed.Topological bi-refringence is expected for photons propagating perpendicularly to the compactification direction.The effect of a topological photom mass on the static properties of electromagnetic fields is also considered for the cases of both twisted and untwisted scalar fields,Our result shows that in the untwisted case the magnetic field is screened along the radial dirction for massive photon modes.while in the twisted case no screening occurs and the magnetic fields merely oscillate. 相似文献
8.
We obtain a lower bound on the spacetime-weighted average of the energy density for the scalar field in four-dimensional flat spacetime. The bound takes the form of a quantum inequality. The inequality does not rely on the quantum state and its form is only related to the weights, namely the spacetime sampling functions which are assumed to be smooth, positive and compactly supported. It is found that the inequality is just equal to the temporal quantum energy inequality. When the characteristic length of the temporal sampling function tends to zero, the lower bound becomes divergent. This is consistent with the fact that the spatial restriction on negative energy density does not exist in four-dimensional spacetime. 相似文献
9.
We examine the energy density produced by a state vector which is the superposition of three single electron states in the Dirac field in the four-dimensional Minkowski spacetime. We derive the conditions on which the energy density can be negative. We then show that the energy density satisfies two quantum inequalities in the ultrarelativistic limit. 相似文献
10.