The stepwise path integral of the relativistic point particle

In this paper we present a stepwise construction of the path integral over relativistic orbits in Euclidean spacetime. It is shown that the apparent problems of this path integral, like the breakdown of the naive Chapman-Kolmogorov relation, can be solved by a careful analysis of the overcounting associated with local and global symmetries. Based on this, the direct calculation of the quantum propagator of the relativistic point particle in the path integral formulation results from a simple and purely geometric construction.Comment: 10 pages, 5 figure

A hidden constraint on the Hamiltonian formulation of relativistic worldlines

Gauge theories with general covariance are particularly reluctant to quantization. We discuss the example of the Hamiltonian formulation of the relativistic point particle that, despite its apparent simplicity, is of crucial importance since a number of point particle systems can be cast into this form on a higher dimensional Rindler background, as recently pointed out by Hojman. It is shown that this system can be equipped with a hidden local, symmetry generating, constraint which on the one hand does not bother the classical evolution and on the other hand simplifies the realization of the path integral quantization. Even though the positive impact of the hidden symmetry is more evident in the Lagrangian version of the theory, it is still present through the suggested Hamiltonian constraint

Properties of galaxies at the faint end of the Hα\alpha luminosity function at z∼0.62z\sim0.62

Studies measuring the star formation rate density, luminosity function, and properties of star-forming galaxies are numerous. However, it exists a gap at $0.5<z<0.8$ in H$\alpha$-based studies. Our main goal is to study the properties of a sample of faint H$\alpha$ emitters at $z\sim0.62$. We focus on their contribution to the faint end of the luminosity function and derived star formation rate density, characterising their morphologies and basic photometric and spectroscopic properties. We use a narrow-band technique in the near-infrared, with a filter centred at 1.06 $\mu$m. The data come from ultra-deep VLT/HAWK-I observations in the GOODS-S field with a total of 31.9 h in the narrow-band filter. We perform a visual classification of the sample and study their morphologies from structural parameters available in CANDELS. Our 28 H$\alpha$-selected sample of faint star-forming galaxies reveals a robust faint-end slope of the luminosity function $\alpha=-1.46_{-0.08}^{+0.16}$. The derived star formation rate density at $z\sim0.62$ is $\rho_\mathrm{SFR} = 0.036_{-0.008}^{+0.012} M_{\odot}~\mathrm{yr^{-1}~Mpc^{-3}}$. The sample is mainly composed of disks, but an important contribution of compact galaxies with S\'ersic indexes $n\sim2$ display the highest specific star formation rates. The luminosity function at $z\sim0.62$ from our ultra-deep data points towards a steeper $\alpha$ when an individual extinction correction for each object is applied. Compact galaxies are low-mass, low-luminosity, and starburst-dominated objects with a light profile in an intermediate stage from early to late types.Comment: Published in Astronomy & Astrophysics. 19 pages, 14 figures. New version includes language edited by the journa

Autocorrelations from emergent bistability in homeostatic spiking neural networks on neuromorphic hardware

A fruitful approach towards neuromorphic computing is to mimic mechanisms of the brain in physical devices, which has led to successful replication of neuronlike dynamics and learning in the past. However, there remains a large set of neural self-organization mechanisms whose role for neuromorphic computing has yet to be explored. One such mechanism is homeostatic plasticity, which has recently been proposed to play a key role in shaping network dynamics and correlations. Here, we study—from a statistical-physics point of view—the emergent collective dynamics in a homeostatically regulated neuromorphic device that emulates a network of excitatory and inhibitory leaky integrate-and-fire neurons. Importantly, homeostatic plasticity is only active during the training stage and results in a heterogeneous weight distribution that we fix during the analysis stage. We verify the theoretical prediction that reducing the external input in a homeostatically regulated neural network increases temporal correlations, measuring autocorrelation times exceeding 500 ms, despite single-neuron timescales of only 20ms, both in experiments on neuromorphic hardware and in computer simulations. However, unlike theoretically predicted near-critical fluctuations, we find that temporal correlations can originate from an emergent bistability.We identify this bistability as a fluctuation-induced stochastic switching between metastable active and quiescent states in the vicinity of a nonequilibrium phase transition. Our results thereby constitute a complementary mechanism for emergent autocorrelations in networks of spiking neurons with implications for future developments in neuromorphic computingEuropean Union Sixth Framework Programme (FP6/2002-2006)Grant Agreement No. 15879 (FACETS)The European Union Seventh Framework Programme (FP7/2007-2013) under Grant Agreements No. 604102 (HBP),No. 269921 (BrainScaleS)No. 243914 (Brain-i-Nets)The Horizon 2020 Framework Programme (H2020/2014-2020)Grant Agreements No. 720270No. 785907No. 945539 (HBP)the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy EXC 2181/1-390900948 (the Heidelberg STRUCTURES Excellence Cluster)The Helmholtz Association Initiative and Networking Fund [Advanced Computing Architectures (ACA)] under Project No. SO-092the Helmholtz Association Initiative and Networking Fund [Advanced Computing Architectures (ACA)] under Project No. SO-092The Spanish Ministry and Agencia Estatal de Investigación (AEI) through Project I+D+i (Reference No. PID2020-113681GBI00)MICIN/AEI/10.13039/501100011033 and FEDER “A way to make EuropeConsejería de Conocimiento, Investigación Universidad, Junta de Andalucía, and European Regional Development FundProject No. P20-00173The Plan Propio de Investigación y Transferencia de la Universidad de GranadaGrant No. INST 39/963-1 FUGG (bwForCluster NEM

RF Power Harvesting Rectenna

Sustainability is one of today\u27s primary engineering objectives. This principle involves system design that minimizes environmentally harmful energy emissions and resource consumption, and maximizes renewable energy practices [1]. Communication antennas transmit wireless signals that can be converted into usable energy. The Rectenna system described in this report, shown in Figure 1, was designed to accomplish this energy conversion, with -5dBm (316µW) minimum power at the rectifier input. Since typical ambient signal power is in the -70dBm (0.1nW) range, the proposed system could only convert passive, relatively high-power microwave band AC signals to DC. The Rectenna system was designed for 1.9GHz signal reception; however, the greatest ambient 1.9GHz signal power measured in Cal Poly’s Microwave Lab was in the -75dBm (31pW) to -70dBm (100pW) range, shown in Table 1. The team provided an external 1.9GHz source (-20dBm to 3dBm) to verify the design. An inset-fed microstrip patch is used as an energy harvesting antenna; the single patch was then arrayed into a 2x2 planar configuration. The designed patch antenna array has a 3dB larger gain, and 1% increased frequency bandwidth compared to the single patch. However, it is unable to harvest sufficient RF power for energy storage. When capturing multiple-source ambient RF signals, an omnidirectional antenna (captures energy in all directions) should be implemented, rather than a directional patch antenna array. The Greinacher rectifier [2] converts RF energy into usable DC power which is multiple times the input RF peak voltage. Simulations show the Greinacher rectifier output voltage is a function of the number of stages and peak input voltage. The antenna and rectifier are matched with |S11| less than -21dB and -5dB, respectively, at 1.9GHz to mitigate power losses. A high-efficiency Main Boost Converter (BQ25504) increases rectifier output DC voltage to 3.1V for charge storage on a capacitor (battery). A Self-Oscillating Boost Converter (SOBC) handles startup when the capacitor is initially discharged. A passive switching circuit was developed to enable source-free switching from the SOBC to the Main Boost Converter. The system yields 29% and 12% maximum power efficiency with -1dBm (794µW) and -5dBm (316µW) input power to the rectifier, respectively

La necesidad de un diálogo con la visión humanista que dio origen a la Universidad Publica en México

En el presente trabajo se enfoca la disonancia entre el discurso oficial y la evaluación de los procesos académicos, sociales y administrativos de las universidades públicas mexicanas. Desde esta problemática, se cuestiona la falta de compromiso con el encuentro auténtico entre las personas, convivencia ferozmente azotada por los estereotipos, prácticas y criterios mercantiles de los gobiernos neoliberales. La propuesta que se percibe a lo largo del trabajo es la de un enfoque humano como pensar crítico, es decir, como una reflexión dispuesta a repensarse desde la perspectiva del otro con el fin de aumentar la comprensión de lo humano, de igual manera y en el mismo sentido, como capacidad para percibir lo superfluo y vano que condiciona, subordina y manipula el concepto de lo humano. La visión convivencial, que privilegia el encuentro con el hombre real, y que está dispuesta a reconfigurarse para no perder el contacto con las personas, se contrapone a la visión instrumental que gusta del encuentro conceptual para controlar y aprovechar la energía de los individuos como un insumo más en la dinámica de la producción. La propuesta tiene su fundamento y anclaje en el anti-positivismo mexicano, que ya desde finales del siglo XIX viene criticando la visión instrumentalista que se instaló en la educación mexicana

Estudio geomecánico para el planeamiento de minado y diseño del proyecto minero El Zarco- 2018

RESUMEN La presente tesis se realizó en la concesión minera “TRES PIRÁMIDES” propiedad de la empresa A.H&H Minería y Construcción S.R.L, políticamente está ubicado en el caserío de Acshupata, distrito de Magdalena, provincia y departamento de Cajamarca en el norte peruano, al Nor Oeste de Cajamarca. En la presente investigación desarrollamos un estudio geomecánico para el planeamiento de minado y el diseño de las canteras, iniciamos haciendo una descripción general, accesos, geología, topografía, datos necesarios para conocer las reservas, posteriormente la evaluación geomecánica en campo y en gabinete; finalmente el diseño de los taludes, altura de banco y berma. En la evaluación geomecánica los macizos rocosos analizados pertenecen a las calizas de la Formación Cajamarca que corresponden a calizas wackstone y packstone. El área se encuentra dentro de una estructura principal que es un pliegue sinclinal cuyo eje pasa por esta formación sedimentaria. Para el presente estudio se ha considerado la clasificación de RMR 89 propuesto por Beniawski, el RQD propuesto por Deere, el GSI por Hoeck Brown y los respectivos análisis en el laboratorio de Mecánica de Rocas de la Universidad Nacional de Ingeniería. Los resultados muestran que son macizos de CLASE II en estudio de campo y CLASE III mediante resultados de laboratorio, y que estos según el análisis de estabilidad se encuentran totalmente estables, una vez que hemos evaluado la calidad y resistencia de la roca procedemos a realizar el diseño de bancos y ángulos de banco y talud.ABSTRACT. The following thesis was developed to a mining concession with “Tres Pirámides” that is property of A.H&H mining and construction company S.R.L., and it is in Acshupata countryside area, district of Magdalena, province and department of Cajamarca stated in the North of Peru. This research we developed a geotechnical study for the planning on mining and the design of mining pits, we start making a general description,, accesses, geology, topography and the needed data to know the reservation of mining, therefore the geo-mechanic assessment in proper field and in office, finally the design of the batter, height of bench and berm. In the geo-mechanic assessment, the solid rocks studied belong to limestone of Formación Cajamarca, that corresponds to lime wackstone and pack stone. The area is inside of a main structure that is a synclinal fold whose axis goes through this sediment formation. To this study we have considered the sorting of RMR 89 proposed by Beniawski, the RQD proposed by Deere, the GSI by Hoeck Brown and the respective analyses at the Rock Mechanic Laboratory of the Universidad Nacional de Ingeniería. The results, and whose stability analysis show a totally stability, after we have evaluated the quality and resistance of the rock we proceeding to make the design of the benches and benches angles including the batter

The GALEX/S4G UV-IR color-color diagram: Catching spiral galaxies away from the Blue Sequence

We obtained GALEX FUV, NUV, and Spitzer/IRAC 3.6$\mu$m photometry for > 2000 galaxies, available for 90% of the S4G sample. We find a very tight "GALEX Blue Sequence (GBS)" in the (FUV-NUV) versus (NUV-[3.6]) color-color diagram which is populated by irregular and spiral galaxies, and is mainly driven by changes in the formation timescale ($\tau$) and a degeneracy between $\tau$ and dust reddening. The tightness of the GBS provides an unprecedented way of identifying star-forming galaxies and objects that are just evolving to (or from) what we call the "GALEX Green Valley (GGV)". At the red end of the GBS, at (NUV-[3.6]) > 5, we find a wider "GALEX Red Sequence (GRS)" mostly populated by E/S0 galaxies that has a perpendicular slope to that of the GBS and of the optical red sequence. We find no such dichotomy in terms of stellar mass (measured by $\rm{M}_{[3.6]}$), since both massive ($M_{\star} > 10^{11} M_{\odot}$) blue and red sequence galaxies are identified. The type that is proportionally more often found in the GGV are the S0-Sa's and most of these are located in high-density environments. We discuss evolutionary models of galaxies that show a rapid transition from the blue to the red sequence on timescale of $10^{8}$years.Comment: 7 pages, 4 figures, 1 table. Accepted for publication in ApJ