Summary
In order to calculate the density of gravitons in the universe, we examine various processes that can contribute to the production of gravitons and we give an estimate of the cross-sections for their production by two photons that react in presence of a gravitational field. We give also the cross-sections for the inverse processes, that is for the destruction of gravitons. After having examined other processes of production, in particular the production by close binary systems of stars, we find that in the case of the evolutionary universe, that is, in a universe with an age of ∼1018 s, the situation is far from equilibrium and the gravitons are still accumulating. At the present stage the mean density of gravitons in the whole universe seems to be ∼ 10−19 erg/cm3.
Riassunto
Si prendono in esame vari processi di produzione e distruzione dei gravitoni e si fa una stima della densità dei gravitoni nell’universo. In particolare si calcolano le sezioni d’urto di produzione di gravitoni da parte di fotoni in presenza di campi gravitazionali esterni quali quelli forniti dalle stelle, dalle galassie e dalle quasar. Nel caso di un universo di tipo evolutivo a cui si attribuisca l’età di 1018 s, si trova che la densità dei gravitoni non ha raggiunto uno stadio di equilibrio ma è in continuo aumento. Attualmente tale densità media sembra essere di ∼ 10−19 erg/cm3.
Реэюме
С целью вычислить плотность гравитонов во Вселенной, мы исследуем раэличные процессы, которые могут дать вклад в рождение гравитонов, и мы даем оценку поперечных сечений для их рождения при столкновении двух фотонов в гравитационном поле. Мы приводим также поперечные сечения для обратных процессов, которые обуславливают раэвал гравитонов. После исследования других процессов рождения, в частности, рождения блиэкими двойными системами эвеэд, мы получаем, что в случае зволюционируюшейся Вселенной, т.е. Вселенной с воэрастом ∼1018 сек, ситуация далека от равновесия, и гравитоны еше аккумулируются. На данном зтапе средняя плотность гравитонов во всей Вселенной равна ∼10−19 зрг/см3.
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This work has been supported by the CNR, GIFCO (Italian Group of Cosmic Physics, Italian National Research Council).
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Boccaletti, D., De Sabbata, V., Gualdi, C. et al. Gravitons in the universe. Nuovo Cimento B (1965-1970) 54, 134–144 (1968). https://doi.org/10.1007/BF02711531
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DOI: https://doi.org/10.1007/BF02711531