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Search Results: 1 - 10 of 145114 matches for " F Gamboa "
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Bose-Einstein condensation theory for any integer spin: approach based in noncommutative quantum mechanics
J. Gamboa,F. Mendez
Physics , 2009,
Abstract: A Bose-Einstein condensation theory for any integer spin using noncommutative quantum mechanics methods is considered. The effective potential is derived as a multipolar expansion in the non-commutativity parameter ($\theta$) and, at second order in $\theta$, our procedure yields to the standard dipole-dipole interaction with $\theta^2$ playing the role of the strength interaction parameter. The generalized Gross-Pitaevskii equation containing non-local dipolar contributions is found. For $^{52}$Cr isotopes $\theta = C_{dd}/4\pi$ becomes $\sim 10^{-11}$ cm and, thus for this value of $\theta$ one cannot distinguish interactions coming from non-commutativity or those of dynamical origin.
Scattering in Three Dimensional Extremal Black Holes
J. Gamboa,F. Mendez
Physics , 2000, DOI: 10.1088/0264-9381/18/2/302
Abstract: An approach to scattering theory in three dimensional AdS spaces is proposed. Firstly we consider the scattering of spinless relativistic particles by a three dimensional extremal black hole and compute the absorption cross section $\sigma_{abs} =J_{abs}/J_{\infty}$ without using {\it in} and {\it out} states. Secondly, we posit a reciprocal space ${\cal H}$ where {\it in} and {\it out} states and the scattering amplitude is defined as in usual scattering theory. We show that both descriptions are equivalent and ${\cal H}$ could be considered as the space where the scattering processes in AdS should be defined.
Quantum Gravity at Very High Energies
J. Gamboa,F. Mendez
Physics , 2000, DOI: 10.1016/S0550-3213(01)00084-0
Abstract: The problem of time and the quantization of three dimensional gravity in the strong coupling regime is studied following path integral methods. The time is identified with the volume of spacetime. We show that the effective action describes an infinite set of massless relativistic particles moving in a curved three-dimensional target space, i.e. a tensionless 3-brane on a curved background. If the cosmological constant is zero the target space is flat and there is no ` ` graviton" propagation (i.e., $G[g_{ij} (2), g_{ij} (1)] = 0$). If the cosmological constant is different from zero, 3D gravity is both classical and quantum mechanically soluble. Indeed, we find the following results: i) The general exact solutions of the Einstein equations are singular at $t=0$ showing the existence of a big-bang in this regime and ii) the propagation amplitude between two geometries $$ vanishes as $t \to 0$, suggesting that big-bang is suppressed quantum mechanically. This result is also valid for $D>3$.
INTERACTION BETWEEN ANIONIC POLYELECTROLYTES AND CTAB MICELLES: A POTENTIOMETRIC STUDY
GAMBOA,C; BARRAZA,R; OLEA,A. F.;
Journal of the Chilean Chemical Society , 2004, DOI: 10.4067/S0717-97072004000400007
Abstract: the interaction between a series of anionic copolymers having variable hydrophobic character with cationic micelles of cetyltrimethylammonium bromide (ctab) has been studied by measuring the free bromide ion concentration. the results are discussed in terms of the effect of polymer concentration on the ionization degree (a) of the ctab micelles. the value of a increases with increasing polymer concentration. the magnitude of this effect depends on the hydrophobicity of the polymer chain, which is determined by the length of the alkyl side chain
Control de malezas con herbicidas y métodos mecánicos en plantaciones jóvenes de café
Sánchez F,Luis; Gamboa,Erbert;
Bioagro , 2004,
Abstract: during the first two years after coffee planting abundant weed control is needed to keep the plantation free of competing plants, which causes high costs and labor time. with the objective of searching for alternative control methods an experiment was performed to evaluate the use of herbicides in a 6 month-old plantation located in bramón, táchira, venezuela. treatments were oxyfluorfen 960 g a.i./ha, and napropamida 2 kg a.i./ha, both diluted in 880 l of water applied with a pack sprayer. additionally, the traditional weed control using machete and back hoe were evaluated. a completely randomized design with five replications and 15 plants per plot were used. the herbicides did not cause damage to the crop, nor affected the growth of the plants (p£ 0.01). oxyfluorfen was the best treatment in maintaining the crop free of weeds for about 90 days as compared to 50 days by the traditional controls.
No axions in light shinning through a wall experiments
Gamboa, J.;Guendelman, E. I.;Mendez, F.
High Energy Physics - Phenomenology , 2007,
Abstract: This paper has been withdrawn and a new version will be submitted soon
Control de malezas con herbicidas y métodos mecánicos en plantaciones jóvenes de café Weed control by herbicides and mechanical methods on early stage of coffee plantations
Luis Sánchez F,Erbert Gamboa
Bioagro , 2004,
Abstract: En los dos primeros a os después de la siembra del café (Coffea arabica L.) se requieren repetidos controles de maleza para mantener el cultivo libre de interferencia, ocasionando altos costos y tiempo de labor. Se realizó un experimento en una plantación de 6 meses de edad, en Bramón estado Táchira, Venezuela, para evaluar herbicidas en esta fase del cultivo. Los tratamientos consistieron en oxyfluorfen 960 g i.a./ha y napropamida 2 kg i.a./ha diluidos en 880 L de agua aplicados con asperjadora de espalda; además de los controles tradicionales con machete y escardilla. Se utilizó un dise o completamente aleatorizado con cinco réplicas y unidades experimentales de 15 plantas. Los herbicidas no ocasionaron da o al cultivo ni afectaron su crecimiento (P<= 0,01). Se concluyó desde el punto de vista del control, que el mejor tratamiento fue oxyfluorfen el cual permitió mantener el cultivo libre de competencia por aproximadamente 90 días en comparación con 50 días en los controles tradicionales. During the first two years after coffee planting abundant weed control is needed to keep the plantation free of competing plants, which causes high costs and labor time. With the objective of searching for alternative control methods an experiment was performed to evaluate the use of herbicides in a 6 month-old plantation located in Bramón, Táchira, Venezuela. Treatments were oxyfluorfen 960 g a.i./ha, and napropamida 2 kg a.i./ha, both diluted in 880 L of water applied with a pack sprayer. Additionally, the traditional weed control using machete and back hoe were evaluated. A completely randomized design with five replications and 15 plants per plot were used. The herbicides did not cause damage to the crop, nor affected the growth of the plants (P<= 0.01). Oxyfluorfen was the best treatment in maintaining the crop free of weeds for about 90 days as compared to 50 days by the traditional controls.
INTERACTION BETWEEN ANIONIC POLYELECTROLYTES AND CTAB MICELLES: A POTENTIOMETRIC STUDY
C GAMBOA,R BARRAZA,A. F. OLEA
Journal of the Chilean Chemical Society , 2004,
Abstract: The interaction between a series of anionic copolymers having variable hydrophobic character with cationic micelles of cetyltrimethylammonium bromide (CTAB) has been studied by measuring the free bromide ion concentration. The results are discussed in terms of the effect of polymer concentration on the ionization degree (a) of the CTAB micelles. The value of a increases with increasing polymer concentration. The magnitude of this effect depends on the hydrophobicity of the polymer chain, which is determined by the length of the alkyl side chain
Quantum Theory of Tensionless Noncommutative p-Branes
J. Gamboa,M. Loewe,F. Mendez
Physics , 2003, DOI: 10.1103/PhysRevD.70.106006
Abstract: The quantum theory involving noncommutative tensionless p-branes is studied following path integral methods. Our procedure allow a simple treatment for generally covariant noncommutative extended systems and it contains, as a particular case, the thermodynamics and the quantum tensionless string theory. The effect induced by noncommutativity in the field space is to produce a confinement among pairing of null p-branes.
Dynamics determines geometry
Sergio A. Hojman,J. Gamboa,F. Mendez
Physics , 2012, DOI: 10.1142/S0217732312501866
Abstract: The inverse problem of calculus of variations and $s$-equivalence are re-examined by using results obtained from non-commutative geometry ideas. The role played by the structure of the modified Poisson brackets is discussed in a general context and it is argued that classical $s$-equivalent systems may be non-equivalent at the quantum mechanical level. This last fact is explicitly discussed comparing different approaches to deal with the Nair-Polychronakos oscillator.
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