Leptogenesis from Soft Supersymmetry Breaking (Soft Leptogenesis)

Soft leptogenesis is a scenario in which the cosmic baryon asymmetry is produced from a lepton asymmetry generated in the decays of heavy sneutrinos (the partners of the singlet neutrinos of the seesaw) and where the relevant sources of CP violation are the complex phases of soft supersymmetry-breaking terms. We explain the motivations for soft leptogenesis, and review its basic ingredients: the different CP-violating contributions, the crucial role played by thermal corrections, and the enhancement of the efficiency from lepton flavour effects. We also discuss the high temperature regime $T > 10^7$ GeV in which the cosmic baryon asymmetry originates from an initial asymmetry of an anomalous $R$-charge, and soft leptogenesis reembodies in $R$-genesis.Comment: References updated. Some minor corrections to match the published versio

Team Relationship and Knowledge Management in Construction Projects in Thailand Part 2: Network Relationship Analysis Using UCINET Software

The study of network relationship using UCINET program in part 1 was inspired by the problematic fragmented structure of a construction project development team. In this paper, the multi-stage project development process as another key factor that underlies the construction industry’s poor performance is addressed. Knowledge management is then proposed as another key solution to achieve the more effective project development in Thailand context. Based on Nonaka and Takeuchi’s 1995 knowledge conversion model, representatives from key project members’ organisations that developed recently complete large commercial residential projects in Bangkok central business area were asked in semi-structured interviews about organisational knowledge management process using a set of standardised questions. The outcomes show the moderate efficiency due to key project members’ unawareness of knowledge potentials. A three-stage framework is also proposed to identify key project members, strengthen network relationship and improve organisational knowledge management capability to achieve the better project development performance

Team Relationship and Knowledge Management in Construction Projects in Thailand Part 1: Network Relationship Analysis Using UCINET Software

Problematic relationship within fragmented team structures and inefficient multi-stage project development processes are the two major issues that affect project development performance in the construction industry. The problems are particularly apparent In Thailand’s developing economy. This paper focuses on the study of relationship among construction project team members at the pre-design appraisal development stage as the first step to improve the competitiveness of project development in Thailand’s construction industry. Recently completed large commercial residential projects in Bangkok’s central business district were used as case studies. For the field research, semi-structured interviews were conducted with a selection of client organisations and key project members using a standardised questionnaire to collect relevant quantitative and qualitative data. UCINET, the social network analysis software, was implemented to analyse quantitative data to reveal the relationship characteristics. The transformed aggregate scores of strength and satisfaction of relationship, as well as some of the project network characteristics like low network density (0.2045 out of 1.000) in selected case study projects, did not appear to be very accommodating to the creation of good relationship. Other network characteristics, including high reciprocity (68.75%), above average reachability (8 out of 11), relatively short (1.405) average geodesic distance and small degree centralisation (27% out degree and 37% in degree) suggested a close relationship among key project members. Moreover, supportive personal and subgroup characteristics such as low to average (1 to 6 out of 11) out and in degree centrality and a high clustering coefficients (0.725 out of 1.000) were considered as the key factors to achieving effective knowledge creation and transfer. This will be explored further in part 2 of this research

Concept and Application of UCINET Software to Study Network Relationship in Construction Projects

As extensively recognised in the reviewed literature, the fragmentation of the project development team and the multi-stage project development process are two underlying factors that significantly affect the construction industry’s unsatisfactory performance and competitiveness. The addressed problems are potentially solved by strong network relationship and effective knowledge management at the pre-design appraisal development stage. This paper focuses on the concept and application of UCINET social network software to study quantitative network relationships among appraisal development team members in selected OTL commercial residential projects in Bangkok, Thailand. Key network characteristics like network density, reciprocity, reachability, geodesic distance as well as personal and subgroup characteristics such as degree centrality, network centralisation, clustering coefficients, cliques, ego network and brokerage can be used to improve project development performance and the industry’s competitiveness based on more effective knowledge creation and transfer

Relationship and knowledge management among construction development project members in Thailand: the clients' perspective

The unsatisfactory performance of the construction industry in Thailand is influenced by the fragmented structure and the inefficient multi-stage project development process. Good relationships, the creation of new knowledge and effective knowledge management is crucial particularly at the development appraisal to achieve improved and sustainable performance in the construction industry. This study is an investigation of the relationships among team members and knowledge management practice in Thailand's construction industry. Semi-structured interviews conducted in the field research with a selection of large client organisations revealed that significant close or network relationship exists between clients and key project team members. However, knowledge management practices were heavily influenced by team members' self-centred nature. There is therefore a need to adopt knowledge management practices to improve project performance at the development appraisal stage as this could have significant knock on effects on subsequent stages. Failure to address relationship and knowledge issues could affect the uptake and sale of development projects

Supersymmetric Leptogenesis

We study leptogenesis in the supersymmetric standard model plus the seesaw. We identify important qualitative differences that characterize supersymmetric leptogenesis with respect to the non-supersymmetric case. The lepton number asymmetries in fermions and scalars do not equilibrate, and are related via a non-vanishing gaugino chemical potential. Due to the presence of new anomalous symmetries, electroweak sphalerons couple to winos and higgsinos, and QCD sphalerons couple to gluinos, thus modifying the corresponding chemical equilibrium conditions. A new constraint on particles chemical potentials corresponding to an exactly conserved $R$-charge, that also involves the number density asymmetry of the heavy sneutrinos, appears. These new ingredients determine the $3\times 4$ matrices that mix up the density asymmetries of the lepton flavours and of the heavy sneutrinos. We explain why in all temperature ranges the particle thermodynamic system is characterized by the same number of independent quantities. Numerical differences with respect to usual treatment remain at the ${\cal O}(1)$ level.Comment: 30 pages, 2 figures. Typos corrected, one reference added. Version published in JCA

Quantum Impurities and the Neutron Resonance Peak in YBa2Cu3O7{\bf YBa_2 Cu_3 O_7}: Ni versus Zn

The influence of magnetic (S=1) and nonmagnetic (S=0) impurities on the spin dynamics of an optimally doped high temperature superconductor is compared in two samples with almost identical superconducting transition temperatures: YBa$_2$(Cu$_{0.97}$Ni$_{0.03}$)$_3$O$_7$ (T$_c$=80 K) and YBa$_2$(Cu$_{0.99}$Zn$_{0.01}$)$_3$O$_7$ (T$_c$=78 K). In the Ni-substituted system, the magnetic resonance peak (which is observed at E$_r \simeq$40 meV in the pure system) shifts to lower energy with a preserved E$_r$/T$_c$ ratio while the shift is much smaller upon Zn substitution. By contrast Zn, but not Ni, restores significant spin fluctuations around 40 meV in the normal state. These observations are discussed in the light of models proposed for the magnetic resonance peak.Comment: 3 figures, submitted to PR

The scaling properties of exchange and correlation holes of the valence shell of second row atoms

We study the exchange and correlation hole of the valence shell of second row atoms using variational Monte Carlo techniques, especially correlated estimates, and norm-conserving pseudopotentials. The well-known scaling of the valence shell provides a tool to probe the behavior of exchange and correlation as a functional of the density and thus test models of density functional theory. The exchange hole shows an interesting competition between two scaling forms -- one caused by self-interaction and another that is approximately invariant under particle number, related to the known invariance of exchange under uniform scaling to high density and constant particle number. The correlation hole shows a scaling trend that is marked by the finite size of the atom relative to the radius of the hole. Both trends are well captured in the main by the Perdew-Burke-Ernzerhof generalized-gradient approximation model for the exchange-correlation hole and energy.Comment: 18 pages, 8 figure

The Afterglow and Environment of the Short GRB111117A

We present multi-wavelength observations of the afterglow of the short GRB111117A, and follow-up observations of its host galaxy. From rapid optical and radio observations we place limits of r \gtrsim 25.5 mag at \deltat \approx 0.55 d and F_nu(5.8 GHz) < 18 \muJy at \deltat \approx 0.50 d, respectively. However, using a Chandra observation at t~3.0 d we locate the absolute position of the X-ray afterglow to an accuracy of 0.22" (1 sigma), a factor of about 6 times better than the Swift-XRT position. This allows us to robustly identify the host galaxy and to locate the burst at a projected offset of 1.25 +/- 0.20" from the host centroid. Using optical and near-IR observations of the host galaxy we determine a photometric redshift of z=1.3 (+0.3,-0.2), one of the highest for any short GRB, and leading to a projected physical offset for the burst of 10.5 +/- 1.7 kpc, typical of previous short GRBs. At this redshift, the isotropic gamma-ray energy is E_{gamma,iso} \approx 3\times10^51 erg (rest-frame 23-2300 keV) with a peak energy of E_{pk} \approx 850-2300 keV (rest-frame). In conjunction with the isotropic X-ray energy, GRB111117A appears to follow our recently-reported E_x,iso-E_gamma,iso-E_pk universal scaling. Using the X-ray data along with the optical and radio non-detections we find that for a blastwave kinetic energy of E_{K,iso} \approx E_{gamma,iso}, the circumburst density is n_0 \sim 3x10^(-4)-1 cm^-3 (for a range of epsilon_B=0.001-0.1). Similarly, from the non-detection of a break in the X-ray light curve at t<3 d, we infer a minimum opening angle for the outflow of theta_j> 3-10 degrees (depending on the circumburst density). We conclude that Chandra observations of short GRBs are effective at determining precise positions and robust host galaxy associations in the absence of optical and radio detections.Comment: ApJ accepted versio