Corante e óleo aromático de Curcuma longa: aditivos naturais para alimentos.

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Quantum Effects in the Spacetime of a Magnetic Flux Cosmic String

In this work we compute the vacuum expectation values of the energy-momentum tensor and the average value of a massive, charged scalar field in the presence of a magnetic flux cosmic string for both zero- and finite-temperature cases.Comment: To appear in the Int. Journal of Modern Phys. A (special issue). Proceedings of the Second International Londrina Winter School on Mathematical Methods in Physics, Londrina, Brazil, August 200

Vinagreira: fonte de antocianinas para alimentos.

bitstream/item/65504/1/CTAA-COM.-TEC.-8-85.pd

Massive scalar field near a cosmic string

The $\zeta$ function of a massive scalar field near a cosmic string is computed and then employed to find the vacuum fluctuation of the field. The vacuum expectation value of the energy-momentum tensor is also computed using a point-splitting approach. The obtained results could be useful also for the case of self-interacting scalar fields and for the finite-temperature Rindler space theory.Comment: 15 pages, standard LaTeX, no figures. Reference [14] correcte

Writing electronic ferromagnetic states in a high-temperature paramagnetic nuclear spin system

In this paper we use the Nuclear Magnetic Resonance (NMR) to write eletronic states of a ferromagnetic system into a high-temperature paramagnetic nuclear spins. Through the control of phase and duration of radiofrequency pulses we set the NMR density matrix populations, and apply the technique of quantum state tomography to experimentally obtain the matrix elements of the system, from which we calculate the temperature dependence of magnetization for different magnetic fields. The effects of the variation of temperature and magnetic field over the populations can be mapped in the angles of spins rotations, carried out by the RF pulses. The experimental results are compared to the Brillouin functions of ferromagnetic ordered systems in the mean field approximation for two cases: the mean field is given by (i) $B=B_0+\lambda M$ and (ii) $B=B_0+\lambda M + \lambda^\prime M^3$, where $B_0$ is the external magnetic field, and $\lambda, \lambda^\prime$ are mean field parameters. The first case exhibits second order transition, whereas the second case has first order transition with temperature hysteresis. The NMR simulations are in good agreement with the magnetic predictions

Vacuum Polarization at Finite Temperature around a Magnetic Flux Cosmic String

We consider a general situation where a charged massive scalar field $\phi(x)$ at finite temperature interacts with a magnetic flux cosmic string. We determine a general expression for the Euclidean thermal Green's function of the massive scalar field and a handy expression for a massless scalar field. With this result, we evaluate the thermal average $$ and the thermal average of the energy-momentum tensor of a nonconformal massless scalar field.Comment: 22 pages, latex, no figure