10,524 research outputs found
Derivatives of tangent function and tangent numbers
In the paper, by induction, the Fa\`a di Bruno formula, and some techniques
in the theory of complex functions, the author finds explicit formulas for
higher order derivatives of the tangent and cotangent functions as well as
powers of the sine and cosine functions, obtains explicit formulas for two Bell
polynomials of the second kind for successive derivatives of sine and cosine
functions, presents curious identities for the sine function, discovers
explicit formulas and recurrence relations for the tangent numbers, the
Bernoulli numbers, the Genocchi numbers, special values of the Euler
polynomials at zero, and special values of the Riemann zeta function at even
numbers, and comments on five different forms of higher order derivatives for
the tangent function and on derivative polynomials of the tangent, cotangent,
secant, cosecant, hyperbolic tangent, and hyperbolic cotangent functions.Comment: 17 page
Semi-Numerical Simulation of Reionization with Semi-Analytical Modeling of Galaxy Formation
In a semi-numerical model of reionization, the evolution of ionization
fraction is simulated approximately by the ionizing photon to baryon ratio
criterion. In this paper we incorporate a semi-analytical model of galaxy
formation based on the Millennium II N-body simulation into the semi-numerical
modeling of reionization. The semi-analytical model is used to predict the
production of ionizing photons, then we use the semi-numerical method to model
the reionization process. Such an approach allows more detailed modeling of the
reionization, and also connects observations of galaxies at low and high
redshifts to the reionization history. The galaxy formation model we use was
designed to match the low- observations, and it also fits the high redshift
luminosity function reasonably well, but its prediction on the star formation
falls below the observed value, and we find that it also underpredicts the
stellar ionizing photon production rate, hence the reionization can not be
completed at without taking into account some other potential
sources of ionization photons. We also considered simple modifications of the
model with more top heavy initial mass functions (IMF), with which the
reionization can occur at earlier epochs. The incorporation of the
semi-analytical model may also affect the topology of the HI regions during the
EoR, and the neutral regions produced by our simulations with the
semi-analytical model appeared less poriferous than the simple halo-based
models.Comment: 13 pages, 8 figures, RAA accepte
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