Effective models of quantum black holes inspired by Loop Quantum Gravity (LQG) have had success in resolving the classical singularity with polymerisation procedures and by imposing the LQG area gap as a minimum area. The singularity is replaced by a hypersurface of transition from black to white holes, and a recent example is the Ashtekar, Olmedo and Singh (AOS) model for a Schwarzschild black hole. More recently, a one-parameter model, with equal masses for the black and white solutions, was suggested by Alonso-Bardaji, Brizuela and Vera (ABBV). An interesting feature of their quantisation is that the angular part of the metric retains its classical form and the horizon area is therefore the same as in the classical theory. In the present contribution we solve the dynamical equations derived from the ABBV effective Hamiltonian and, by applying the AOS minimal area condition, we obtain the scaling of the polymerisation parameter with the black hole mass. We then show that this effective model can also describe Planck scale black holes, and that the curvature and quantum corrections at the horizon are small even at this scale. By generating the exterior metric through a phase rotation in the dynamical variables, we also show that, for an asymptotic observer, the Kretschmann scalar is the same as in the classical Schwarzschild solution, but with a central mass screened by the quantum fluctuations.

Black hole (networking)

Loop Quantum Cosmology

10.1088/1361-6382/acdbff

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Citations (7)

The influence of precursor preparation on the superconducting properties of Bi(2223) tapes

IEEE Transactions on Applied Superconductivity (1999)

Alexander Polasek Shouxin Xia Maurı́cio Barreto Lisboa Márcio Antônio Sens E.T. Serra

The effect of preparation of precursor powders on the formation of Bi-2223 phase and critical current density (J/sub c/) of OPIT tapes, was studied. The precursors were prepared by "one-powder" and "two-powder" methods. The results indicate that a sufficiently large fraction of second phases in the precursors is crucial for obtaining pure 2223 phase and high J/sub c/ values. It is also revealed that the (Sr,Ca)/sub 2/CuO/sub 3/ second phase promotes a faster phase transformation of 2212 to 2223 than other second phases in the precursors. Tapes prepared with "one-powder" precursor achieved J/sub c/ of 25.5 kA/cm/sup 2/, while the J/sub c/ for the tapes made from "two-powder" precursors had values of about 12 kA/cm/sup 2/.

10.1109/77.785012

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Citations (3)

Superconducting properties of actinide compounds and other recent results

Physica B+C (1987)

J. L. Smith Z. Fisk J. D. Thompson J.O. Willis H. A. Borges

10.1016/0378-4363(87)90146-x

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Citations (5)

Evolution of the structural phase transition in CeAg in the low pressure range

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) (1985)

S. Horn H. A. Borges J. D. Thompson R. D. Parks

Previous studies have suggested that the cooperative structural transition observed in CeAg near 15/sup 0/K at ambient pressure evolves into the martensitic transition which is observed under applied pressure. By utilizing very small pressures, we have observed the birth of the martensitic transition and demonstrated that the two transitions are uncoupled.

Ambient pressure

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Identification and control of the total oxidation sites in the reaction of oxidative coupling of methane over sulfated lanthana catalysts

Catalysis Today (1994)

H. A. Borges Sylvie Lacombe C. Mirodatos

Potassium sulfate

Partial oxidation

10.1016/0920-5861(94)80150-9

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Magnetism, Structure and Superconductivity in Ce_2RhIn_8

arXiv (Cornell University) (2002)

M. Nicklas V. A. Sidorov H. A. Borges P. G. Pagliuso C. Petrović

We report the discovery of pressure-induced superconductivity, with T_c=2 K, in the heavy-fermion antiferromagnet Ce_2RhIn_8, where superconductivity and magnetic order coexist over an extended pressure interval. A T-linear resistivity in the normal state, accessed by an applied magnetic field, does not appear to derive from the existence of a 2D quantum-critical spin-density wave.

Magnetism

Spin density wave

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