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Mahsa Berahman

Publications and source records attributed to Mahsa Berahman.

2 recordsLinked to original sources

SVR Algorithm as a Tool for More Optimal Intergalactic Medium Simulation in the Epoch of Reionization

All kinds of simulations of the intergalactic medium, such as hydrodynamic simulation, N-body simulation, numerical and semi-numerical simulation, etc., have been used to realize the history of this medium. In addition, emulators also have become widely used in recent years. Especially because they are very fast, they are used in many works instead of actual complete simulations. Emulators are trained with the help of simulator results and can work with very high accuracy similar to real simulators. Usually, reliable machine learning algorithms, such as neural networks, are used to program these emulators. In this work, we show that one of the best machine learning algorithms that can be used in general and have extremely high accuracy is the Support Vector Regression algorithm. This algorithm works better than the Multilayer Perceptron algorithm not only from the practical point of view but also from the theoretical point of view. To prove this issue, we have considered the 21SSD hydrodynamical simulation in addition to the theoretical arguments, and we have used both algorithms to be trained by this simulation for comparison. Finally, we have shown that the Support Vector Regression algorithm can be a much better and more accurate algorithm than neural network algorithms in future emulations, and by mastering it, one can neglect other algorithms with full confidence. Although this work is focused only on an intergalactic medium simulation in the Epoch of Reionization, it can be used for all other simulations regardless of their type. In other words, it can be employed for all hydrodynamic simulations, N-body simulations, etc. in all cosmic epochs and rely on its results.

astro-ph.CO

New Accretion Constraint on the Evaporation of Primordial Black Holes

In this paper, we have investigated the processes of evaporation and accretion of primordial black holes during the radiation-dominated era and the matter-dominated era. This subject is very important since usually these two processes are considered independent of each other. In other words, previous works consider them in such a way that they do not have a direct effect on each other, and as a result, their effects on the mass of primordial black holes are calculated separately. The calculations of this paper indicate that assuming these two processes independently of each other will lead to wrong results that only give correct answers within certain limits. In fact, in general, it is a mistake to consider the static state for the event horizon of primordial black holes and perform calculations related to their evaporation, while the radius of primordial black holes is constantly changing due to accretion. In addition, we have shown that considering the dynamic event horizon in some masses and in some times can lead to the shutdown of the Hawking evaporation process. This study is much more accurate and detailed than our previous study. These calculations show well the mass evolution of primordial black holes from the time of formation to the end of the matter-dominated era, taking into account both the main processes governing black holes, evaporation and accretion.

astro-ph.CO