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A new perspective on cosmology in Loop Quantum Gravity¹
by E. Alesci and F. Cianfrani

We present a new cosmological model derived from Loop Quantum Gravity. The formulation is based on a projection of the kinematical Hilbert space of the full theory down to a subspace representing the proper arena for an inhomogeneous Bianchi I model. This procedure gives a direct link between the full theory and its cosmological sector, thus it allows to test the complete canonical quantization program and to shed light on the foundation of Loop Quantum Cosmology. Furthermore, the emerging quantum cosmological model represents a concrete implementation of a discrete quantum Universe and it opens new perspectives on the phenomenology of early cosmology.

Morphology transition at depinning in a solvable model of interface growth in a random medium ²
by Hiroki Ohta, Martin Luc Rosinberg and Gilles Tarjus

We propose a simple, exactly solvable, model of interface growth in a random medium that is a variant of the zero-temperature random-field Ising model on the Cayley tree. This model is shown to have a phase diagram (critical depinning field vs. disorder strength) qualitatively similar to that obtained numerically on the cubic lattice. We then introduce a specifically tailored random graph that allows an exact asymptotic analysis of the height and width of the interface. We characterize the change of morphology of the interface as a function of the disorder strength, a change that is found to take place at a multicritical point along the depinning-transition line.

Superconductivity and physical properties of strongly electron correlated compounds La_nRu_3n−1B_2n (n = 1, 2, and 3)³
by Hechang Lei and H. Hosono

We examined the physical properties of homologous La_nRu_3n−1B_2n (n = 1, 2, and 3) series including a new compound of n = 2. All of these compounds showed strong electron-electron correlation characterized by large Wilson ratio. In contrast to LaRu₂B₂ and La₂Ru₅B₄ that show normal metal behaviors down to 1.8 K, we discover La₃Ru₈B₆ is an intermediately coupled BCS superconductor with T_c ∼ 3.2K. The experimental and theoretical calculation results suggest that the emergence of superconductivity in La₃Ru₈B₆ can be attributed to the rather large density of states at E_F when compared to other two compounds.

Momentum-resolved electronic structure at a buried interface from soft X-ray standing-wave angle-resolved photoemission⁴
by A. X. Gray, J. Minár, L. Plucinski, M. Huijben, A. Bostwick, E. Rotenberg, S.‐H. Yang, J. Braun, A. Winkelmann, G. Conti, D. Eiteneer, A. Rattanachata, A. A. Greer, J. Ciston, C. Ophus, G. Rijnders, D. H. A. Blank, D. Doennig, R. Pentcheva, J. B. Kortright, C. M. Schneider, H. Ebert and C. S. Fadley

Angle-resolved photoemission spectroscopy (ARPES) is a powerful technique for the study of electronic structure, but it lacks a direct ability to study buried interfaces between two materials. We address this limitation by combining ARPES with soft X-ray standing-wave (SW) excitation (SWARPES), in which the SW profile is scanned through the depth of the sample. We have studied the buried interface in a prototypical magnetic tunnel junction La_0.7Sr_0.3MnO₃/SrTiO₃. Depth-and momentum-resolved maps of Mn 3 d e_g and t_2g states from the central, bulk-like and interface-like regions of La_0.7Sr_0.3MnO₃ exhibit distinctly different behavior consistent with a change in the Mn bonding at the interface. We compare the experimental results to state-of-the-art density-functional and one-step photoemission theory, with encouraging agreement that suggests wide futur…

1. E. Alesci and F. Cianfrani. 2013. A new perspective on cosmology in Loop Quantum Gravity. EPL, 104, 10001. DOI: 10.1209/0295-5075/104/10001 [↩]
2. Hiroki Ohta, Martin Luc Rosinberg and Gilles Tarjus. 2013. Morphology transition at depinning in a solvable model of interface growth in a random medium. EPL, 104, 16003. DOI: 10.1209/0295-5075/104/16003 [↩]
3. Hechang Lei and H. Hosono. 2013. Superconductivity and physical properties of strongly electron correlated compounds La_nRu_3n−1B_2n (n = 1, 2, and 3). EPL, 104, 17003. DOI: 10.1209/0295-5075/104/17003 [↩]
4. A. X. Gray, et al. 2013. Momentum-resolved electronic structure at a buried interface from soft X-ray standing-wave angle-resolved photoemission. EPL, 104, 17004. DOI: 10.1209/0295-5075/104/17004 [↩]

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