Charge Superselection Sectors for Scalar QED on the Lattice

The lattice model of scalar quantum electrodynamics (Maxwell field coupled to a complex scalar field) in the Hamiltonian framework is discussed. It is shown that the algebra of observables ${\cal O}({\Lambda})$ of this model is a $C^*$-algebra, generated by a set of gauge-invariant elements satisfying the Gauss law and some additional relations. Next, the faithful, irreducible and non-degenerate representations of ${\cal O}({\Lambda})$ are found. They are labeled by the value of the total electric charge, leading to a decomposition of the physical Hilbert space into charge superselection sectors. In the Appendices we give a unified description of spinorial and scalar quantum electrodynamics and, as a byproduct, we present an interesting example of weakly commuting operators, which do not commute strongly

Origin of bulk uniaxial anisotropy in zinc-blende dilute magnetic semiconductors

It is demonstrated that the nearest neighbor Mn pair on the GaAs (001) surface has a lower energy for the [-110] direction comparing to the [110] case. According to the group theory and the Luttinger's method of invariants, this specific Mn distribution results in bulk uniaxial in-plane and out-of-plane anisotropies. The sign and magnitude of the corresponding anisotropy energies determined by a perturbation method and ab initio computations are consistent with experimental results.Comment: 5 pages, 1 figur

Magnitude and crystalline anisotropy of hole magnetization in (Ga,Mn)As

Theory of hole magnetization Mc in zinc-blende diluted ferromagnetic semiconductors is developed relaxing the spherical approximation of earlier approaches. The theory is employed to determine Mc for (Ga,Mn)As over a wide range of hole concentrations and a number of crystallographic orientations of Mn magnetization. It is found that anisotropy of Mc is practically negligible but the obtained magnitude of Mc is significantly greater than that determined in the spherical approximation. Its sign and value compares favorably with the results of available magnetization measurements and ferromagnetic resonance studies.Comment: 5 pages, 3 figure

Efficiency of supplementing saccharomyces cerevisiae var. ellipsoideus for improved growth performance and carcass yield in broilers

The use of dietary additives is becoming a very interesting practise to improve animal health and performance in poultry production. Thepax® is a prebiotic that includes inactivated Saccharomyces cerevisiae Var. ellipsoideus cells and nutrients such as vitamins, enzymes, amino acids and short chain polypeptides. The effects of supplementing diet by Thepax® via potable water on growth and carcass yield were studied in broilers. Two treatments, an active with Thepax® and a control treatment, were used on 120 male and female chicks of the Hubbard JV breed. Birds were divided into 6 groups of 20 birds each managed on floor and received the same starter, grower and finisher concentrates based on maize and soybean meal during a 37 days trial period. Thepax®(0.5 ml of the additive for 1 litre of water) was used during only one month. Body weight and daily growth rate seemed to increase by 6.2% and 6.4%, respectively, in birds receiving Thepax® compared to control birds. Feed conversion ratio and water intake were similar (P≥0.201) for both groups of birds. The effect of the additive was important on birds’ health. The mortality rate decreased (P=0.0241) by around 71% in birds receiving Thepax®compared to that in control birds. Furthermore, the active group of birds deposited (P = 0.0172) less abdominal fat (-35.2%) without affecting carcass yield. Positive effects of Thepax® with its structure and composition may be an important additional source of nutrients supports growth and enhance feed ingredients digestibility and beneficial intestinal microflora activity in broilers. In conclusion, Thepax® administered to broilers in drinkable water may improve birds’ health and reduce abdominal fat without compromising carcass yield

Quantum transport and mobility spectrum of topological carriers in (001) SnTe/PbTe heterojunctions

Measurements of magnetotransport in SnTe/PbTe heterojunctions grown by the MBE technique on (001) undoped CdTe substrates were performed. At low magnetic fields, quantum corrections to conductivity were observed that may be attributed to the presence of topological states at the junction interface. For a sample with 5 nm thick SnTe layer, the data analysis suggests that midgap states are actually gapped. However, the phase coherence effects in 10 nm and 20 nm SnTe/PbTe samples are fully explained assuming existence of gapless Dirac cones. Magnetotransport at higher magnetic fields is described in the framework of mobility spectrum analysis (MSA). We demonstrate that the electron- and hole-like peaks observed simultaneously for all SnTe/PbTe heterojunctions may originate from the concave and convex parts of the energy isosurface for topological states -- and not from the existence of quasiparticles both carrying negative and positive charges. This interpretation is supported by numerical calculations of conductivity tensor components for gapless (100) Dirac cones, performed within a classical model and based on the solutions of Boltzmann transport equation. Our approach shows the feasibility of MSA in application to magnetotransport measurements on topological matter

Heralded generation of entangled photon pairs

Entangled photons are a crucial resource for quantum communication and linear optical quantum computation. Unfortunately, the applicability of many photon-based schemes is limited due to the stochastic character of the photon sources. Therefore, a worldwide effort has focused in overcoming the limitation of probabilistic emission by generating two-photon entangled states conditioned on the detection of auxiliary photons. Here we present the first heralded generation of photon states that are maximally entangled in polarization with linear optics and standard photon detection from spontaneous parametric down-conversion. We utilize the down-conversion state corresponding to the generation of three photon pairs, where the coincident detection of four auxiliary photons unambiguously heralds the successful preparation of the entangled state. This controlled generation of entangled photon states is a significant step towards the applicability of a linear optics quantum network, in particular for entanglement swapping, quantum teleportation, quantum cryptography and scalable approaches towards photonics-based quantum computing

The nature of the unresolved extragalactic soft CXB

In this paper we investigate the power spectrum of the unresolved 0.5-2 keV CXB with deep Chandra 4 Ms observations in the CDFS. We measured a signal which, on scales >30", is significantly higher than the Shot-Noise and is increasing with the angular scale. We interpreted this signal as the joint contribution of clustered undetected sources like AGN, Galaxies and Inter-Galactic-Medium (IGM). The power of unresolved cosmic sources fluctuations accounts for \sim 12% of the 0.5-2 keV extragalactic CXB. Overall, our modeling predicts that \sim 20% of the unresolved CXB flux is made by low luminosity AGN, \sim 25% by galaxies and \sim 55% by the IGM (Inter Galactic Medium). We do not find any direct evidence of the so called Warm Hot Intergalactic Medium (i.e. matter with 10^5K<T<10^7K and density contrast {\delta} <1000), but we estimated that it could produce about 1/7 of the unresolved CXB. We placed an upper limit to the space density of postulated X-ray-emitting early black hole at z>7.5 and compared it with SMBH evolution models.Comment: 15 pages, 9 figures, accepted by MNRA

Playing in the academic field: Non-native English-speaking academics in UK business schools

This paper draws on Bourdieu's concepts of field, habitus and capital to explore the ways in which working in English as a non-native language influences foreign academics' performance of academic habitus and the level of their symbolic capital necessary for the achievement of success within UK higher education. Empirically, it is based on interviews with 54 non-native English-speaking academics employed in UK business schools. Our findings point to advantages and disadvantages associated with being a non-native English-speaking academic, to strategies deployed by individuals to enhance their linguistic capital, and to the importance of language not merely as a tool of communication but as a key factor enabling individuals to perform academic habitus in the UK academic field. We reflect on whether, and if so, how, the UK academic field is changing as a result of the increased presence within it of non-UK-born academics and, in particular, the fact of their professional functioning in English as a non-native language

Profaning the sacred in leadership studies: A reading of Murakami's A Wild Sheep Chase

The leadership literature is full of stories of heroic self-sacrifice. Sacrificial leadership behaviour, some scholars conclude, is to be recommended. In this article we follow Keith Grint's conceptualization of leadership as necessarily pertaining to the sacred, but-drawing on Giorgio Agamben's notion of profanation-we highlight the need for organization scholars to profane the sacralizations embedded in leadership thinking. One example of this, which guides us throughout the article, is the novel A Wild Sheep Chase, by the Japanese author Haruki Murakami. By means of a thematic reading of the novel, we discuss how it contributes to profaning particular notions of sacrifice and the sacred in leadership thinking. In the novel, self-sacrifice does not function as a way of establishing a leadership position, but as a way to avoid the dangers associated with leadership, and possibly redeem humans from their current collective urge to become leaders. Inspired by Murakami's fictional example, we call organization scholars to engage in profanation of leadership studies and, in doing so, open new vistas for leadership theory and practice. © The Author(s) 2012