Constants of motion associated with alternative Hamiltonians

It is shown that if a non-autonomous system of $2n$ first-order ordinary differential equations is expressed in the form of the Hamilton equations in terms of two different sets of coordinates, $(q_{i}, p_{i})$ and $(Q_{i}, P_{i})$, then the determinant and the trace of any power of a certain matrix formed by the Poisson brackets of the $Q_{i}, P_{i}$ with respect to $q_{i}, p_{i}$, are constants of motion

Nuevo centro Las Cruces: renovación urbana, capacitación y emprendimiento en la ciudad de Bogotá

Trabajo de gradoEl proyecto nuevo Centro Las Cruces es una propuesta urbana y arquitectónica que presenta un cambio en la imagen de un sector tradicional del centro de Bogotá. Teniendo de base conceptos como el hábitat y la sostenibilidad el modelo de ciudad incorpora nuevos elementos arquitectónicos que delimitan un borde pretendiendo de esta manera cambiar la percepción de inseguridad, inequidad y pobreza no sólo de sus habitantes sino también del resto de la ciudad.PregradoArquitect

Geometric thermodynamics: black holes and the meaning of the scalar curvature

In this paper we show that the vanishing of the scalar curvature of Ruppeiner-like metrics does not characterize the ideal gas. Furthermore, we claim through an example that flatness is not a sufficient condition to establish the absence of interactions in the underlying microscopic model of a thermodynamic system, which poses a limitation on the usefulness of Ruppeiner's metric and conjecture. Finally, we address the problem of the choice of coordinates in black hole thermodynamics. We propose an alternative energy representation for Kerr-Newman black holes that mimics fully Weinhold's approach. The corresponding Ruppeiner's metrics become degenerate only at absolute zero and have non-vanishing scalar curvatures.Comment: LaTeX file, no figure

Analytical Modeling of Interference Aware Power Control for the Uplink of Heterogeneous Cellular Networks

Inter-cell interference is one of the main limiting factors in current Heterogeneous Cellular Networks (HCNs). Uplink Fractional Power Control (FPC) is a well known method that aims to cope with such limiting factor as well as to save battery live. In order to do that, the path losses associated with Mobile Terminal (MT) transmissions are partially compensated so that a lower interference is leaked towards neighboring cells. Classical FPC techniques only consider a set of parameters that depends on the own MT transmission, like desired received power at the Base Station (BS) or the path loss between the MT and its serving BS, among others. Contrary to classical FPC, in this paper we use stochastic geometry to analyze a power control mechanism that keeps the interference generated by each MT under a given threshold. We also consider a maximum transmitted power and a partial compensation of the path loss. Interestingly, our analysis reveals that such Interference Aware (IA) method can reduce the average power consumption and increase the average spectral efficiency. Additionally, the variance of the interference is reduced, thus improving the performance of Adaptive Modulation and Coding (AMC) since the interference can be better estimated at the MT.Comment: 13 pages, 1 table and 7 figures. This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Combination methods for HIV prevention in men who have sex with men (MSM)

This is the protocol for a review and there is no abstract. The objectives are as follows: This review seeks to examine the effectiveness of prevention interventions for MSM that combine at least two of the three categories of intervention modality (biomedical, behavioural and structural) compared either to other HIV prevention interventions or to minimal/no HIV prevention. Below, descriptions of the criteria that will be used to categorise intervention components are provided under the heading Types of interventions' and the full list of outcomes of interest are provided in the section Types of outcome measures'. All planned comparisons are detailed in the section Data synthesis', followed by the planned variables of interest for subgroup and meta-regression analyses