MG13 - Talk detail |
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Participant |
Singh, Tejinder | |||||||
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Institution |
Tata Institute of Fundamental Research - Homi Bhabha Road - Mumbai - Maharashtra - India | |||||||
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Session |
AT4 |
Accepted |
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Time |
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Talk |
Oral abstract |
Title |
Modified gravity as a common cause for the origin of flat galaxy rotation curves and cosmic acceleration | |||||
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Abstract |
We propose a fourth order modified gravity whose solution we consider for two different space-time metrics : the non-relativistic weak-field Newtonian approximation, and the spatially flat Robertson-Walker metric. We show that in the weak field limit one obtains a fourth order modification of the Poisson equation, which induces a Yukawa modification of the inverse square law. A consequence is flattening of galaxy rotation curves, implying that modified gravity could serve as an alternative to dark matter. In the cosmological case the modified gravity results in a fourth order correction to the Einstein equations. We show that these corrections induce a cosmic acceleration in the present cosmological epoch, and hence serve as an alternative to dark energy. We discuss the possible underlying physics which could give rise to such a fourth order modification of general relativity. |
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Session |
GT5 |
Accepted |
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Time |
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Talk |
Oral abstract |
Title |
Quantum Field Theory without Classical Time, and a Generalized Quantum Dynamics | |||||
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Abstract |
There ought to exist a description of quantum field theory which does not depend on an external classical time. To achieve this goal, in a recent paper we have proposed a non-commutative special relativity in which space-time and matter degrees of freedom are treated as classical matrices with arbitrary commutation relations, and a space-time line element is defined using a trace. In the present paper, following the theory of Trace Dynamics, we construct a statistical thermodynamics for the non-commutative special relativity, and show that one arrives at a generalized quantum dynamics in which space and time are non-classical and have an operator status. In a future work, we will show how standard quantum theory on a classical space-time background is recovered from here. Reference: arXiv:1203.6518 [gr-qc] submitted to Nucl. Phys. B |
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