Why Do They (Still) Sing Stories? Singing Narratives in Tanjung Bunga (Eastern Flores, Lamaholot, Indonesia)

In eastern Flores, on the Tanjung Bunga peninsula (among Western Lamaholot speakers), several times a year, ritual narratives (opak) are performed on a square dancing area, where all the clans of the same ceremonial land meet. Three types of narrative are sung, according to three kinds of rituals. The article explains the context, content and performance details of these stories, performed all night long. Why do the various clans continue to sing all these narrative? What values do these long poems have for people who sing them? Until now, studies on this subject have been remarkably few, and not even a partial transcription or translation of these narratives is available. This article offers a preliminary insight into these sung narratives, to show how vital they still are in eastern Flores

Money versus Credit Rationing: Evidence for the National Banking Era, 1880-1914

In this paper we examine the evidence for two competing views of how monetary and financial disturbances influenced the real economy during the national banking era, 1880-1914. According to the monetarist view, monetary disturbances affected the real economy through changes on the liability side of the banking system's balance sheet independent of the composition of bank portfolios. According to the credit rationing view, equilibrium credit rationing in a world of asymmetric information can explain short-run fluctuations in real output. Using structural VARs we incorporate monetary variables in credit models and credit variables in monetarist models, with inconclusive results. To resolve this ambiguity, we invoke the institutional features of the national banking era. Most of the variation in bank loans is accounted for by loans secured by stock, which in turn reflect volatility in the stock market. When account is taken of the stock market, the influence of credit in the VAR model is greatly reduced, while the influence of money remains robust. The breakdown of the composition of bank loans into stock market loans (traded in open asset markets) and other business loans (a possible setting for credit rationing) reveals that other business loans remained remarkably stable over the business cycle.

Ion-beam modification of the magnetic properties of GaMnAs epilayers

We study the controlled introduction of defects in GaMnAs by irradiating the samples with energetic ion beams, which modify the magnetic properties of the DMS. Our study focuses on the low-carrier-density regime, starting with as-grown GaMnAs films and decreasing even further the number of carriers, through a sequence of irradiation doses. We did a systematic study of magnetization as a function of temperature and of the irradiation ion dose. We also performed in-situ room temperature resistivity measurements as a function of the ion dose. We observe that both magnetic and transport properties of the samples can be experimentally manipulated by controlling the ion-beam parameters. For highly irradiated samples, the magnetic measurements indicate the formation of magnetic clusters together with a transition to an insulating state. The experimental data are compared with mean-field calculations for magnetization. The independent control of disorder and carrier density in the calculations allows further insight on the individual role of this two factors in the ion-beam-induced modification of GaMnAs.Comment: 9 pages, 9 figure

Zero- and one-dimensional magnetic traps for quasi-particles

We investigate the possibility of trapping quasi-particles possessing spin degree of freedom in hybrid structures. The hybrid system we are considering here is composed of a semi-magnetic quantum well placed a few nanometers below a ferromagnetic micromagnet. We are interested in two different micromagnet shapes: cylindrical (micro-disk) and rectangular geometry. We show that in the case of a micro-disk, the spin object is localized in all three directions and therefore zero-dimensional states are created, and in the case of an elongated rectangular micromagnet, the quasi-particles can move freely in one direction, hence one-dimensional states are formed. After calculating profiles of the magnetic field produced by the micromagnets, we analyze in detail the possible light absorption spectrum for different micromagnet thicknesses, and different distances between the micromagnet and the semimagnetic quantum well. We find that the discrete spectrum of the localized states can be detected via spatially-resolved low temperature optical measurement.Comment: 15 pages, 9 figure

Entanglement in the One-dimensional Kondo Necklace Model

We discuss the thermal and magnetic entanglement in the one-dimensional Kondo necklace model. Firstly, we show how the entanglement naturally present at zero temperature is distributed among pairs of spins according to the strength of the two couplings of the chain, namely, the Kondo exchange interaction and the hopping energy. The effect of the temperature and the presence of an external magnetic field is then investigated, being discussed the adjustment of these variables in order to control the entanglement available in the system. In particular, it is indicated the existence of a critical magnetic field above which the entanglement undergoes a sharp variation, leading the ground state to a completely unentangled phase.Comment: 8 pages, 13 EPS figures. v2: four references adde

Experimental implementation of a NMR entanglement witness

Entanglement witnesses (EW) allow the detection of entanglement in a quantum system, from the measurement of some few observables. They do not require the complete determination of the quantum state, which is regarded as a main advantage. On this paper it is experimentally analyzed an entanglement witness recently proposed in the context of Nuclear Magnetic Resonance (NMR) experiments to test it in some Bell-diagonal states. We also propose some optimal entanglement witness for Bell-diagonal states. The efficiency of the two types of EW's are compared to a measure of entanglement with tomographic cost, the generalized robustness of entanglement. It is used a GRAPE algorithm to produce an entangled state which is out of the detection region of the EW for Bell-diagonal states. Upon relaxation, the results show that there is a region in which both EW fails, whereas the generalized robustness still shows entanglement, but with the entanglement witness proposed here with a better performance

Magnetic effects in sulfur-decorated graphene

The interaction between two different materials can present novel phenomena that are quite different from the physical properties observed when each material stands alone. Strong electronic correlations, such as magnetism and superconductivity, can be produced as the result of enhanced Coulomb interactions between electrons. Two-dimensional materials are powerful candidates to search for the novel phenomena because of the easiness of arranging them and modifying their properties accordingly. In this work, we report magnetic effects of graphene, a prototypical non-magnetic two-dimensional semi-metal, in the proximity with sulfur, a diamagnetic insulator. In contrast to the well-defined metallic behaviour of clean graphene, an energy gap develops at the Fermi energy for the graphene/sulfur compound with decreasing temperature. This is accompanied by a steep increase of the resistance, a sign change of the slope in the magneto-resistance between high and low fields, and magnetic hysteresis. A possible origin of the observed electronic and magnetic responses is discussed in terms of the onset of low-temperature magnetic ordering. These results provide intriguing insights on the search for novel quantum phases in graphene-based compounds.Comment: 6 pages and 5 figure

Role of Disorder on the Quantum Critical Point of a Model for Heavy Fermions

A zero temperature real space renormalization group (RG) approach is used to investigate the role of disorder near the quantum critical point (QCP) of a Kondo necklace (XY-KN) model. In the pure case this approach yields $J_{c}=0$ implying that any coupling $J \not = 0$ between the local moments and the conduction electrons leads to a non-magnetic phase. We also consider an anisotropic version of the model ($X-KN$), for which there is a quantum phase transition at a finite value of the ratio between the coupling and the bandwidth, $(J/W)$. Disorder is introduced either in the on-site interactions or in the hopping terms. We find that in both cases randomness is irrelevant in the $X-KN$ model, i.e., the disorder induced magnetic-non-magnetic quantum phase transition is controlled by the same exponents of the pure case. Finally, we show the fixed point distributions $P_{J}(J/W)$ at the atractors of the disordered, non-magnetic phases.Comment: 5 pages, 3 figure