Quantization of Reissner-Nordstr\"{o}m Black Holes and Their Non-Singular Quantum Behavior

Quantization of different regions of the Reissner-Nordstr\"{o}m space time (charged black hole) is done in the framework of loop quantum gravity. The geometry of Reissner-Nordstr\"{o}m space-time is expressed in terms of Ashtekar variables which form the classical phase space of such a black hole. Using the loop quantization of phase space, the issue of singularity avoidance of such a black hole is addressed; based on spherically symmetry reduced models of loop quantum gravity, the operator analogue of the diverging factor of scalar curvature of the charged black hole is constructed and is shown to exhibit an upper bounded spectrum. This local criterion, together with the global one (non-singular quantum evolution equation) proves the avoidance of charged black hole singularity in symmetry reduced models of loop quantum gravity.Comment: To be published in the proceeding of Quantum Theory: Reconsideration of Foundations-6 (QTRF-6

A fast approach for overcomplete sparse decomposition based on smoothed L0 norm

In this paper, a fast algorithm for overcomplete sparse decomposition, called SL0, is proposed. The algorithm is essentially a method for obtaining sparse solutions of underdetermined systems of linear equations, and its applications include underdetermined Sparse Component Analysis (SCA), atomic decomposition on overcomplete dictionaries, compressed sensing, and decoding real field codes. Contrary to previous methods, which usually solve this problem by minimizing the L1 norm using Linear Programming (LP) techniques, our algorithm tries to directly minimize the L0 norm. It is experimentally shown that the proposed algorithm is about two to three orders of magnitude faster than the state-of-the-art interior-point LP solvers, while providing the same (or better) accuracy.Comment: Accepted in IEEE Transactions on Signal Processing. For MATLAB codes, see (http://ee.sharif.ir/~SLzero). File replaced, because Fig. 5 was missing erroneousl

A walk in the noncommutative garden

This text is written for the volume of the school/conference "Noncommutative Geometry 2005" held at IPM Tehran. It gives a survey of methods and results in noncommutative geometry, based on a discussion of significant examples of noncommutative spaces in geometry, number theory, and physics. The paper also contains an outline (the ``Tehran program'') of ongoing joint work with Consani on the noncommutative geometry of the adeles class space and its relation to number theoretic questions.Comment: 106 pages, LaTeX, 23 figure

Cancer registry in Iran: A brief overview

Cancer registry is an important tool for any successful cancer control program. The first formal cancer related data from Iran were published in 1956. In 1969, observations documenting a high incidence of esophageal cancer in the Caspian Littoral, urged researchers to set up the first population-based cancer registry in this region. This cancer registry was established jointly by University of Tehran and the International Agency for Research on Cancer (IARC). In 1976, another cancer registry started its activities in Fars Province. In 1984, the Parliament passed a bill mandating the report of all tissues "diagnosed or suspected as cancer tissue" to the Ministry of Health. While only 18% of all estimated cancer cases were reported in first reports, this rate increased to 81% in 2005 In 1998, Tehran Population-Based Cancer Registry started to collect data from cases of cancer referred to the treatment and diagnostic facilities throughout the Tehran metropolis. Digestive Disease Research Center, Tehran University of Medical Sciences, established four new population-based cancer registries in Northern Iran and another in Kerman Province in the south. These five provinces have a total population of about 9.5 million, and constitute about 16% of the total population of Iran. While the pathology-based cancer registration is in place, we hope that the addition of the population-based cancer registries, and establishment of new registries in poorly-covered areas, will improve cancer reporting in the country

Level Crossing Analysis of the Stock Markets

We investigate the average frequency of positive slope $\nu_{\alpha}^{+}$, crossing for the returns of market prices. The method is based on stochastic processes which no scaling feature is explicitly required. Using this method we define new quantity to quantify stage of development and activity of stocks exchange. We compare the Tehran and western stock markets and show that some stocks such as Tehran (TEPIX) and New Zealand (NZX) stocks exchange are emerge, and also TEPIX is a non-active market and financially motivated to absorb capital.Comment: 6 pages and 4 figure

Application of Multifractal Measures to Tehran Price Index

We report an empirical study of Tehran Price Index (TEPIX). To analyze our data we use various methods like as, rescaled range analysis ($R/S$), modified rescaled range analysis (Lo's method), Detrended Fluctuation Analysis (DFA) and generalized Hurst exponents analysis. Based on numerical results, the scaling range of TEPIX returns is specified, long memory effect or long range correlation property in this market is investigated, characteristic exponent for probability distribution function of TEPIX returns is derived and finally the stage of development in Tehran Stock Exchange is determined.Comment: 19 pages, 6 figure

Minimizing delay in construction projects in Tehran, Iran

Construction industry is one of the most profitable sectors in Iran’s economic. Delay is common problem in the construction projects in Iran. This research, by considering the main causes of delay, prepared appropriate suggestions to minimize delay in construction projects in Tehran (Capital of Iran). Literature review provided up to date information with current literature and based on reviewing past publications. The questionnaires were distributed among respondents who are involved in the construction project in Tehran, Iran. The process of data analysis and discussions were conducted based on the questionnaire survey to identify the frequency of occurrence and severity affect of delay as well as findings the most effective methods of minimizing delay in Tehran’s construction projects. As a result of this study, respondents believe that ‘Delay in payment to contractor’ by client, ‘Difficulties in financing’ by contractor, ‘Slowness in decision making’ by client and ‘Poor site management’ by contractor are the most frequent and severe causes of delay in Tehran construction projects. Moreover the negative effects of delay on construction projects are: Cost Overrun, Change in Schedule and Liquidated Damage. Furthermore, the most effectiveness methods of minimizing delay are as follows: Pay progress payment to the contractor on time’ by client, ‘Accurate initial cost and time estimates’ by client and contractor, ‘Competent personnel of contractor / sub-contractor’ by contractor. Finally and based on the findings of this research, there were some recommendation to minimize the rate of delay in construction project in Tehran