Niraj Upadhyay | Jadavpur University (original) (raw)
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Papers by Niraj Upadhyay
Reproductive Toxicology, 2003
Physical Review D, 1999
Incorporating a realistic model for accretion of ultra-relativistic particles by primordial black... more Incorporating a realistic model for accretion of ultra-relativistic particles by primordial blackholes (PBHs), we study the evolution of an Einstein-de Sitter universe consisting of PBHs embedded in a thermal bath from the epoch sim10−33\sim 10^{-33}sim10−33 sec to sim5times10−9\sim 5\times 10^{-9}sim5times10−9 sec. In this paper we use Barrow et al's ansatz to model blackhole evaporation in which the modified Hawking temperature goes to zero in the limit of the blackhole attaining a relic state with mass simmpl\sim m_{pl}simmpl. Both single mass PBH case as well as the case in which blackhole masses are distributed in the range 8times102−3times1058\times 10^2 - 3\times 10^58times102−3times105 gm have been considered in our analysis. Blackholes with mass larger than sim105\sim 10^5sim105 gm appear to survive beyond the electroweak phase transition and, therefore, successfully manage to create baryon excess via X−barXX-\bar XX−barX emissions, averting the baryon number wash-out due to sphalerons. In this scenario, we find that the contribution to the baryon-to-entropy ratio by PBHs of initial mass mmm is given by simepsilonzeta(m/1gm)−1\sim \epsilon \zeta (m/1 {gm})^{-1}simepsilonzeta(m/1gm)−1, where epsilon\epsilonepsilon and zeta\zetazeta are the CP-violating parameter and the initial mass fraction of the PBHs, respectively. For epsilon\epsilon epsilon larger than sim10−4\sim 10^{-4}sim10−4, the observed matter-antimatter asymmetry in the universe can be attributed to the evaporation of PBHs.
Physical Review D, 1999
Incorporating a realistic model for accretion of ultrarelativistic particles by primordial black ... more Incorporating a realistic model for accretion of ultrarelativistic particles by primordial black holes (PBHs), we study the evolution of an Einstein-de Sitter universe consisting of PBHs embedded in a thermal bath from the epoch ~10-33 sec to ~5×10-9 sec. In this paper we use the ansatz of Barrow et al. to model black hole evaporation in which the modified Hawking temperature goes to zero in the limit of the black hole attaining a relic state with a mass ~mPl. Both the single mass PBH case as well as the case in which black hole masses are distributed in the range 8×102-3×105 g have been considered in our analysis. Black holes with a mass larger than ~105 g appear to survive beyond the electroweak phase transition and, therefore, successfully manage to create baryon excess via X-X¯ emissions, averting the baryon number washout due to sphalerons. In this scenario, we find that the contribution to the baryon-to-entropy ratio by PBHs of initial mass m is given by ~ɛζ(m/1 g)-1, where ɛ and ζ are the CP-violating parameter and the initial mass fraction of the PBHs, respectively. For ɛ larger than ~10-4, the observed matter-antimatter asymmetry in the universe can be attributed to the evaporation of PBHs.
Reproductive Toxicology, 2003
Physical Review D, 1999
Incorporating a realistic model for accretion of ultra-relativistic particles by primordial black... more Incorporating a realistic model for accretion of ultra-relativistic particles by primordial blackholes (PBHs), we study the evolution of an Einstein-de Sitter universe consisting of PBHs embedded in a thermal bath from the epoch sim10−33\sim 10^{-33}sim10−33 sec to sim5times10−9\sim 5\times 10^{-9}sim5times10−9 sec. In this paper we use Barrow et al's ansatz to model blackhole evaporation in which the modified Hawking temperature goes to zero in the limit of the blackhole attaining a relic state with mass simmpl\sim m_{pl}simmpl. Both single mass PBH case as well as the case in which blackhole masses are distributed in the range 8times102−3times1058\times 10^2 - 3\times 10^58times102−3times105 gm have been considered in our analysis. Blackholes with mass larger than sim105\sim 10^5sim105 gm appear to survive beyond the electroweak phase transition and, therefore, successfully manage to create baryon excess via X−barXX-\bar XX−barX emissions, averting the baryon number wash-out due to sphalerons. In this scenario, we find that the contribution to the baryon-to-entropy ratio by PBHs of initial mass mmm is given by simepsilonzeta(m/1gm)−1\sim \epsilon \zeta (m/1 {gm})^{-1}simepsilonzeta(m/1gm)−1, where epsilon\epsilonepsilon and zeta\zetazeta are the CP-violating parameter and the initial mass fraction of the PBHs, respectively. For epsilon\epsilon epsilon larger than sim10−4\sim 10^{-4}sim10−4, the observed matter-antimatter asymmetry in the universe can be attributed to the evaporation of PBHs.
Physical Review D, 1999
Incorporating a realistic model for accretion of ultrarelativistic particles by primordial black ... more Incorporating a realistic model for accretion of ultrarelativistic particles by primordial black holes (PBHs), we study the evolution of an Einstein-de Sitter universe consisting of PBHs embedded in a thermal bath from the epoch ~10-33 sec to ~5×10-9 sec. In this paper we use the ansatz of Barrow et al. to model black hole evaporation in which the modified Hawking temperature goes to zero in the limit of the black hole attaining a relic state with a mass ~mPl. Both the single mass PBH case as well as the case in which black hole masses are distributed in the range 8×102-3×105 g have been considered in our analysis. Black holes with a mass larger than ~105 g appear to survive beyond the electroweak phase transition and, therefore, successfully manage to create baryon excess via X-X¯ emissions, averting the baryon number washout due to sphalerons. In this scenario, we find that the contribution to the baryon-to-entropy ratio by PBHs of initial mass m is given by ~ɛζ(m/1 g)-1, where ɛ and ζ are the CP-violating parameter and the initial mass fraction of the PBHs, respectively. For ɛ larger than ~10-4, the observed matter-antimatter asymmetry in the universe can be attributed to the evaporation of PBHs.