Self-Gravitating Phase Transitions: Point Particles, Black Holes and Strings

We compute the quantum string entropy S_s(m,j) of the microscopic string states of mass m and spin j in two physically relevant backgrounds: Kerr (rotating) black holes and de Sitter (dS) space-time. We find a new formula for the quantum gravitational entropy S_{sem} (M, J), as a function of the usual Bekenstein-Hawking entropy S_{sem}^(0)(M, J). We compute the quantum string emission by a black hole in de Sitter space-time (bhdS). In all these cases: (i) strings with the highest spin, and (ii) in dS space-time, (iii) quantum rotating black holes, (iv) quantum dS regime, (v) late bhdS evaporation, we find a new gravitational phase transition with a common distinctive universal feature: A square root branch point singularity in any space-time dimensions. This is the same behavior as for the thermal self-gravitating gas of point particles (de Vega-Sanchez transition), thus describing a new universality class.Comment: Invited lecture at `Statistical Mechanics of Non-Extensive Systems', Observatoire de Paris, 24-25 October 2005, to be published in a Special issue of `Les Comptes rendus de l'Academie des sciences', Elsevie

Hawking Radiation in String Theory and the String Phase of Black Holes

The quantum string emission by Black Holes is computed in the framework of the `string analogue model' (or thermodynamical approach), which is well suited to combine QFT and string theory in curved backgrounds (particulary here, as black holes and strings posses intrinsic thermal features and temperatures). The QFT-Hawking temperature T_H is upper bounded by the string temperature T_S in the black hole background. The black hole emission spectrum is an incomplete gamma function of (T_H - T_S). For T_H << T_S, it yields the QFT-Hawking emission. For T_H \to T_S, it shows highly massive string states dominate the emission and undergo a typical string phase transition to a microscopic `minimal' black hole of mass M_{\min} or radius r_{\min} (inversely proportional to T_S) and string temperature T_S. The semiclassical QFT black hole (of mass M and temperature T_H) and the string black hole (of mass M_{min} and temperature T_S) are mapped one into another by a `Dual' transform which links classical/QFT and quantum string regimes. The string back reaction effect (selfconsistent black hole solution of the semiclassical Einstein equations with mass M_+ (radius r_+) and temperature T_+) is computed. Both, the QFT and string black hole regimes are well defined and bounded: r_{min} leq r_+ \leq r_S, M_{min} \leq M_+ \leq M, T_H \leq T_+ \leq T_S. The string `minimal' black hole has a life time tau_{min} \simeq \frac{k_B c}{G \hbar} T^{-3}_S.Comment: LaTex, 31 pages, no figure

Adaptación a la Normativa vigente de los enlaces de Collbató y Esparreguera Nord en la Autovía A-2

El projecte d'adaptació a la normativa vigent del dos enllaços consecutius de la Autovia A-2 entre Collbató i Esparreguera Nord consisteix en la construcció de dues vies de servei, una en cada sentit, de connexió directa entre els dos enllaços i la millora d'aquests dos enllaços amb la construcció de tres rotondes amb el seu corresponent enllumenat i la millora de les condicions de drenatge, senyalització i abalisament.Amb aquest treballs es milloren les condicions de circulació i seguretat del trànsit així com les condicions d'explotació de la via

Valuation of a Startup: Zoom Case Study

This paper provides an overview of the main attributes that define a startup, laying out its stages of development and sources of financing, which are mainly through equity, allowing stakeholders to own part of the business. Also, this paper provides a view on the high-risk nature of a startup, which tends to have operational losses at early stages of development and consequently, high risk of failure. Besides, this research shows that, even though startups operate in any industry, tech and finance are the most successful sectors in the recent years in terms of number of unicorns. The current environment of rising interest rates also affects valuations due to the increase in the risk-free rate, and consequently, the company's cost of capital, which cause valuations to fall. Also, high interest rates increase the interest expense, and thus, companies can spend less money on capital investments, which may affect future earnings growth. The exhaustive company and market analysis of Zoom as of October 2020 shows that Zoom is the clear market leader in the videoconferencing industry, accounting for around 48% of the Daily Active Users in October 2020. This is thanks to the expansion driven by the pandemic lockdowns, which forced people to perform their work-related activities from home. However, competitors in the videoconferencing industry might be able to increase their market share in relation to Zoom since the big incumbent players (e.g., Google Meet, Microsoft Teams etc.) are part of larger corporations which are better capitalized and more skill full when facing a potential future slowdown of the videoconferencing paradigm. The case study of this paper focuses on valuing Zoom on October 2020 using several valuation methodologies. The outcome of the case study provides a share value of between $344.5 and$440.6, which is aligned with the estimations made by several investment banks in that period of time. However, several elements in the case study such as a very high EV/Revenue multiple, indicated that Zoom was overvalued at that time due to the expansion driven by the pandemic lockdowns

Germination and emergence of corn (Zea mays, L) as a function of soil physical parameters

Tesis para obtener el grado de Magister Scientiae en Soil Science, de la Oregon State University, en diciembre de 1988Rates of germination and emergence of corn were measured as influenced by soil physical parameters using blotter paper and a sandy loam soil as growth media. The corn seeds used were a hybrid of Funk's (DJ7xLH93). Experimental conditions were soil temperature of 20°C, 25°C, 30°C, and 35°C, soil water potential of -33, -100, -500, and -1000 kPa, soil bulk density 1.29 and 1.36 Mg/m³ and seeding depth of 3 and 7 cm. For the germination experiment seeds were put in contact with polyethylene glycol at solution concentrations to produce the desired water potentials. Treatment temperatures were maintained in a growth chamber and germination was evaluated every twelve hours. The number of hours required to obtain 50 and 80% germination was significantly increased by lowering either temperature or water potential. Although significant interactions were measured, temperature and water potential affected germination in different ways. Time to attain 80% of germination decreased as temperature increased until the optimum of 30°C was reached. Decreased osmotic potential levels progressively delayed and reduced germination. Time to germination increased greatly below -500 kPa. For emergence experiments seeds were planted in soil packed in covered containers which were placed in a growth chamber. Effects of soil temperature, soil water potential, bulk density, and seeding depth were evaluated. Bulk densities of 1.29 and 1.36 Mg/m³ , were achieved by no compaction and compaction. The two seeding depth were 3 and 7 cm. Time needed for emergence was influenced by soil temperature more than by any other variable. The time for emergence decreased progressively with lowering of soil water potential, lowering temperature or with increase in seeding depth. No significant differences resulted from increasing bulk density. In both the germination and emergence experiments, changes in temperature were more important than changes in water potential at high water potential. However this relation was reversed at water potentials lower than -500 kPa, where changes in water potential were more important than changes in temperature. The minimum time for both germination and emergence occurred at 30°C, at all water potentials. Effect of seeding depth was more important than effect of bulk density for time to emergence. Increases in time were between 20-30% as the seeding depth increased from 3 to 7 cm. Compaction began to limit seedling emergence at 1.44 Mg/m³.EEA Hilario AscasubiFil: Sanchez, Ramon Mauricio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Hilario Ascasubi; Argentin