Charge ordering at the interface in (LaMnO3_3)2n_{2n}/(SrMnO3_3)n_n superlattices as the origin of their insulating state

We have performed ab initio calculations within the LDA+U method in the multilayered system (LaMnO$_3$)$_{2n}$ / (SrMnO$_3$)$_n$. Our results suggest a charge-ordered state that alternates Mn$^{3+}$ and Mn$^{4+}$ cations in a checkerboard in-plane pattern is developed at the interfacial layer, leading to a gap opening. Such an interfacial charge-ordered situation would be the energetically favored reconstruction between LaMnO$_3$ and SrMnO$_3$. This helps understanding the insulating behavior observed experimentally in these multilayers at intermediate values of $n$, whose origin is known to be due to some interfacial mechanism.Comment: 5 pages, 4 figure

The exotic fraction among unassociated Fermi sources

Revealing the nature of unassociated high-energy (> 100 MeV) gamma-ray sources remains a challenge 35 years after their discovery. Of the 934 gamma-ray sources at high Galactic latitude (|b| > 15 degrees) in the First Fermi-LAT catalogue (1FGL), 316 have no obvious associations at other wavelengths. In this paper, we apply the K-means unsupervised classification algorithm to isolate potential counterparts for 18 unassociated Fermi sources contained within a 3000 square degree `overlap region' of the sky intensively covered in radio and optical wavelengths. Combining our results with previous works, we reach potential associations for 119 out of the 128 Fermi sources within said region. If these associations are correct, we estimate that less than 20% of all remaining unassociated 1FGL sources at high Galactic latitude (|b| > 15 degrees) might host `exotic' counterparts distinct from known classes of gamma-ray emitters. Potentially even these outliers could be explained by high-redshift/dust-obscured analogues of the associated sample or by intrinsically faint radio objects. Although such estimate leaves some room for novel discoveries, it severely restricts the possibility of detecting dark matter subhaloes and other unconventional types of gamma-ray emitters in the 1FGL. In closing, we argue that the identification of Fermi sources at the low end of the flux density distribution will be a complex process that might only be achieved through a clever combination of refined classification algorithms, multi-wavelength efforts, and dedicated optical spectroscopy.Comment: 7 pages, 5 figures, 2 table

Dual Fabry-Perot filter for measurement of CO rotational spectra: design and application to the CO spectrum of Venus

We present the design of a harmonic resonant filter that can be used with a Fourier transform spectrometer (FTS) for simultaneous measurement of a series of lines in the CO rotational ladder. To enable studies of both broad CO absorptions in Venus and modestly red-shifted CO emission from external galaxies, relatively broad (approximately 10-30-GHz FWHM) transmission passbands are desirable. Because a single low-finesse Fabry Perot (FP) etalon has insufficient interline rejection, a dual-FP etalon was considered. Such a design provides significantly better interband rejection and somewhat more flattopped transmission spikes. A prototype filter of this type, made of two thin silicon disks spaced by an air gap, has been constructed and used with our FTS at the Caltech Submillimeter Observatory for simultaneous measurement of the four submillimeter CO transitions in the atmosphere of Venus that are accessible from the ground

Atmospheric dispersion and the implications for phase calibration

The success of any ALMA phase-calibration strategy, which incorporates phase transfer, depends on a good understanding of how the atmospheric path delay changes with frequency (e.g. Holdaway & Pardo 2001). We explore how the wet dispersive path delay varies for realistic atmospheric conditions at the ALMA site using the ATM transmission code. We find the wet dispersive path delay becomes a significant fraction (>5 per cent) of the non-dispersive delay for the high-frequency ALMA bands (>160 GHz, Bands 5 to 10). Additionally, the variation in dispersive path delay across ALMA's 4-GHz contiguous bandwidth is not significant except in Bands 9 and 10. The ratio of dispersive path delay to total column of water vapour does not vary significantly for typical amounts of water vapour, water vapour scale heights and ground pressures above Chajnantor. However, the temperature profile and particularly the ground-level temperature are more important. Given the likely constraints from ALMA's ancillary calibration devices, the uncertainty on the dispersive-path scaling will be around 2 per cent in the worst case and should contribute about 1 per cent overall to the wet path fluctuations at the highest frequencies.Comment: 13 pages, 10 figures, ALMA Memo 59

Pleadings, Proof, and Judgment: A Unifed Theory of Civil Litigation

The U.S. Supreme Court’s recent pleadings decisions—Bell Atlantic Corp. v. Twombly and Ashcroft v. Iqbal—have injected considerable chaos into the system of civil litigation. The decisions impose an uncertain “plausibility” requirement and appear to endorse an increased power of district courts to dismiss complaints—a power that may be employed in an unprincipled, normatively problematic manner. The current pleading issues resemble similar issues that have arisen with summary judgment and judgment as a matter of law. This Article argues that there has been a significant failure at both the doctrinal and theoretical levels to relate these three procedural devices to the evidentiary proof process in particular and the system of civil litigation as a whole. It introduces a theory of “procedural accuracy” that explains, clarifies, and provides content to the standards for each device, explains how the theory fits, and explains important aspects of the doctrine for each device. Finally, and most importantly, I defend the theory and its standards as normatively desirable in light of procedural values that underlie the system of civil litigation as a whole

Theoretical and experimental study of AC loss in HTS single pancake coils

The electromagnetic properties of a pancake coil in AC regime as a function of the number of turns is studied theoretically and experimentally. Specifically, the AC loss, the coil critical current and the voltage signal are discussed. The coils are made of Bi2Sr2Ca2Cu3O10/Ag (BiSCCO) tape, although the main qualitative results are also applicable to other kinds of superconducting tapes, such as coated conductors. The AC loss and the voltage signal are electrically measured using different pick up coils with the help of a transformer. One of them avoids dealing with the huge coil inductance. Besides, the critical current of the coils is experimentally determined by conventional DC measurements. Furthermore, the critical current, the AC loss and the voltage signal are simulated, showing a good agreement with the experiments. For all simulations, the field dependent critical current density inferred from DC measurements on a short tape sample is taken into account.Comment: 22 pages, 15 figures; contents extended (sections 3.2 and 4); one new figure (figure 5) and two figures replaced (figures 3 and 8); typos corrected; title change

Group Agency and Legal Proof; or, Why the Jury Is an “It”

Jurors decide whether certain facts have been proven according to the applicable legal standards. What is the relationship between the jury, as a collective decision-making body, on one hand, and the views of individual jurors, on the other? Is the jury merely the sum total of the individual views of its members? Or do juries possess properties and characteristics of agency (for example, beliefs, knowledge, preferences, intentions, plans, and actions) that are in some sense distinct from those of its members? This Article explores these questions and defends a conception of the jury as a group agent with agency that may differ from that of its members. The Article then argues that this conception of the jury contains important implications for law and legal proof. These implications are both theoretical and practical. On the theoretical side, recent debates in evidence law have focused on whether legal proof is probabilistic or explanatory in nature. These debates, however, have largely assumed a single, unified fact-finder (whether jury or judge). The group-level perspective reveals new conceptual problems for the probabilistic theory that are alleviated by the explanatory theory; it thus provides further vindication for the explanatory account. On the practical side, the conception of the jury as a group agent, coupled with the explanatory account of proof, clarifies doctrinal issues on whether, and when, jurors must agree on factual details. In both criminal and civil cases, these issues have caused considerable confusion and uncertainty for courts and commentators