Geometric Bremsstrahlung in the Early Universe
نویسندگان
چکیده
We discuss photon emission from particles decelerlated by the cosmic expansion. This can be interpretated as a kind of bremsstrahlung induced by the Universe geometry. In the high momentum limit its transition probability does not depend on detailed behavior of the expansion. This may play an important role when massless particle emission is discussed in the early Universe.
منابع مشابه
Cosmological Constraints on Large Extra Dimensions
We calculate the production of massive Kaluza-Klein(KK) modes via nucleon-nucleon gravi-bremsstrahlung in the early universe. Overproduction of these states would result in early matter domination and therefore a low age for the universe so it is possible to place constraints on the number and size of large extra dimensions. The constraints are stronger than those from Sn1987a.
متن کاملDilaton and axion bremsstrahlung from collisions of cosmic (super)strings
We calculate dilaton and axion radiation generated in the collision of two straight initially unexcited strings and give a rough cosmological estimate of dilaton and axion densities produced via this mechanism in the early universe.
متن کاملA Comparative Study into “Gere Geometric Designs” in Islamic Architecture and Principle of “Perceptual Creation” in the Mystical Thoughts of Ibn Arabi
This article is an analytic and comparative study into abstract patterns of geometric designs, as one of the most significant spaces in the Islamic architecture, and the principle of perceptual creation. It has a comparative approach to investigate equivalence, effigy, and analogies between the micro and macro systems (in the hierarchical system of the universe). In the mystical cosmology of Ib...
متن کاملارزیابی کولیماتورهای لایهای در تصویربرداری تابش ترمزی حین رادیو دارو درمانی با فسفر-32
Background and purpose: Imaging which is used in nuclear medicine is done using emit gamma rays whereas therapy in nuclear medicine is performed by applying radionuclide’s which emit beta radiation. Using Bremsstrahlung is a new field which is recently introduced in imaging. In the Bremsstrahlung imaging, collimator design should not be based on energy peak and whole energy spectrum should be c...
متن کاملGeometric Model of Quintessence
On basis of modification of Einstein’s gravitational equations by adding the term f(R) ∝ βR , a geometric model of quintessence is proposed. The evolution equation for the scale factor a of the Universe is analyzed for the two parameters n = 2 and n = 4/3, which were preferred by previous studies of the early Universe. Another choice of parameters n and β is proposed from the following reasons:...
متن کامل