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Register a new userThe quantum structure of spacetime at the Planck scale and quantum fields
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We propose uncertainty relations for the different coordinates of spacetime events, motivated by Heisenbergs principle and by Einsteins theory of classical gravity. A model of Quantum Spacetime is then discussed where the commutation relations exactly implement our uncertainty relations. We outline the definition of free fields and interactions over QST and take the first steps to adapting the usual perturbation theory. The quantum nature of the underlying spacetime replaces a local interaction by a specific nonlocal effective interaction in the ordinary Minkowski space. A detailed study of interacting QFT and of the smoothing of ultraviolet divergences is deferred to a subsequent paper. In the classical limit where the Planck length goes to zero, our Quantum Spacetime reduces to the ordinary Minkowski space times a two component space whose components are homeomorphic to the tangent bundle TS^2 of the 2-sphere. The relations with Connes theory of the standard model will be studied elsewhere.
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There is a growing evidence that due to quantum gravity effects the effective spacetime dimensionality might change in the UV. In this letter we investigate this hypothesis by using quantum fields to derive the UV behaviour of the static, two point sources potential. We mimic quantum gravity effects by using non-commutative fields associated to a Lie group momentum space with a Planck mass curvature scale. We find that the static potential becomes finite in the short-distance limit. This indicates that quantum gravity effects lead to a dimensional reduction in the UV or, alternatively, that point-like sources are effectively smoothed out by the Planck scale features of the non-commutative quantum fields.
Almost all theories of Quantum Gravity predict modifications of the Heisenberg Uncertainty Principle near the Planck scale to a so-called Generalized Uncertainty Principle (GUP). Recently it was shown that the GUP gives rise to corrections to the Schrodinger and Dirac equations, which in turn affect all non-relativistic and relativistic quantum Hamiltonians. In this paper, we apply it to superconductivity and the quantum Hall effect and compute Planck scale corrections. We also show that Planck scale effects may account for a (small) part of the anomalous magnetic moment of the muon. We obtain (weak) empirical bounds on the undetermined GUP parameter from present-day experiments.
We derive the stochastic description of a massless, interacting scalar field in de Sitter space directly from the quantum theory. This is done by showing that the density matrix for the effective theory of the long wavelength fluctuations of the field obeys a quantum version of the Fokker-Planck equation. This equation has a simple connection with the standard Fokker-Planck equation of the classical stochastic theory, which can be generalised to any order in perturbation theory. We illustrate this formalism in detail for the theory of a massless scalar field with a quartic interaction.
We investigate the quantum radiation produced by an Unruh-De Witt detector in a uniformly accelerating motion coupled to the vacuum fluctuations. Quantum radiation is nonvanishing, which is consistent with the previous calculation by Lin and Hu [Phys. Rev. D 73, 124018 (2006)]. We infer that this quantum radiation from the Unruh-De Witt detector is generated by the nonlocal correlation of the Minkowski vacuum state, which has its origin in the entanglement of the state between the left and the right Rindler wedges.
I use Unified Spinor Fields (USF), to discuss the creation of magnetic monopoles during preinflation, as excitations of the quantum vacuum coming from a condensate of massive charged vector bosons. For a primordial universe with total energy $M_p$, and for magnetic monopoles created with a total Planck magnetic charge $q_M=q_P=pm e/sqrt{alpha}$ and a total mass $m_M$, it is obtained after quantisation of the action that the fine-structure constant is given by: $alpha= frac{5}{6} left(1- frac{16 ,m_M}{5 ,M_p}right) ,left(frac{e}{q_M}right)^2$. If these magnetic monopoles were with total magnetic charge $q_M=pm e$ and a small mass $m=m_M/n$, there would be a large number of small quantum magnetic monopoles which could be candidates to explain the presence of dark matter with a $30.97,%$ of the energy in the primordial universe at the Planck era. The case of milli-magnetically charged particles is also analysed. We demonstrate that magnetic monopoles (MM) with masses less than $3.6times 10^3$ GeV, can exist with a very small charges of up to $10^{-14},e$, which are quantities of interest for searches to be performed in the ATLAS and MoEDAL experiments.
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