Event by Event Net Charge Fluctuations

We present analyses of event-by-event dynamical net charge fluctuations measured in 130 and 200 GeV Au Au collisions with the STAR detector. The dynamical net charge fluctuations are evaluated using the $\nu_{+-,dyn}$ observable. Dynamical fluctuations measured in Au Au collisions at 130 and 200 GeV are finite, and exceed charge conservation limits. They deviate from a perfect 1/N scaling and provide an indication that the collision dynamics varies with collision centrality.Comment: 6 pages, 3 figures, Proc of 19th Nuclear Dynamics Conf at Breckenridge, Colorado, Feb 8-15, 200

BaNiF4: an electric field-switchable weak antiferromagnet

We show that in the antiferromagnetic ferroelectric BaNiF4 the Dzyaloshinskii-Moriya interaction leads to a small canting of the magnetic moments, away from the easy axis, resulting in a noncollinear magnetic structure. The canting corresponds to an additional "weak" antiferromagnetic order parameter whose orientation is determined by the polar structural distortion and can be reversed by switching the ferroelectric polarization with an electric field. Our results point the way to a more general coupling mechanism between structural distortions and magnetic order parameters in magnetoelectric multiferroics which can be exploited in the design of electric field-switchable magnets.Comment: 4 pages, 4 figure

X-ray Isophote Shapes and the Mass of NGC 3923

We present analysis of the shape and radial mass distribution of the E4 galaxy NGC 3923 using archival X-ray data from the ROSAT PSPC and HRI. The X-ray isophotes are significantly elongated with ellipticity e_x=0.15 (0.09-0.21) (90% confidence) for semi-major axis a\sim 10h^{-1}_70 kpc and have position angles aligned with the optical isophotes within the estimated uncertainties. Applying the Geometric Test for dark matter, which is independent of the gas temperature profile, we find that the ellipticities of the PSPC isophotes exceed those predicted if M propto L at a marginal significance level of 85% (80%) for oblate (prolate) symmetry. Detailed hydrostatic models of an isothermal gas yield ellipticities for the gravitating matter, e_mass=0.35-0.66 (90% confidence), which exceed the intensity weighted ellipticity of the R-band optical light, = 0.30 (e_R^max=0.39). We conclude that mass density profiles with rho\sim r^{-2} are favored over steeper profiles if the gas is essentially isothermal (which is suggested by the PSPC spectrum) and the surface brightness in the central regions (r<~15") is not modified substantially by a multi-phase cooling flow, magnetic fields, or discrete sources. We argue that these effects are unlikely to be important for NGC 3923. (The derived e_{mass} range is very insensitive to these issues.) Our spatial analysis also indicates that the allowed contribution to the ROSAT emission from a population of discrete sources with Sigma_x propto Sigma_R is significantly less than that indicated by the hard spectral component measured by ASCA.Comment: 14 pages (6 figures), To Appear in MNRA

X-ray Constraints on the Intrinsic Shape of the Lenticular Galaxy NGC 1332

We have analyzed ROSAT PSPC X-ray data of the optically elongated S0 galaxy NGC 1332 with the purposes of constraining the intrinsic shape of its underlying mass and presenting a detailed investigation of the uncertainties resulting from the assumptions underlying this type of analysis. The X-ray isophotes are elongated with ellipticity $0.10 - 0.27$ (90% confidence) for semi-major axes 75\arcsec -90\arcsec and have orientations consistent with the optical isophotes (ellipticity $\sim 0.43$). The spectrum is poorly constrained by the PSPC data and cannot rule out sizeable radial temperature gradients or an emission component due to discrete sources equal in magnitude to the hot gas. Using (and clarifying) the "geometric test" for dark matter, we determined that the hypothesis that mass-traces-light is not consistent with the X-ray data at 68% confidence and marginally consistent at 90% confidence independent of the gas temperature profile. Detailed modeling gives constraints on the ellipticity of the underlying mass of \epsilon_{mass} = 0.47 - 0.72 (0.31 - 0.83) at 68% (90%) confidence for isothermal and polytropic models. The total mass of the isothermal models within a=43.6 kpc (D = 20h^{-1}_{80} Mpc) is M_{tot} = (0.38 - 1.7) \times 10^{12}M_{\sun} (90% confidence) corresponding to total blue mass-to-light ratio \Upsilon_B = (31.9 - 143) \Upsilon_{\sun}. Similar results are obtained when the dark matter is fit directly using the known distributions of the stars and gas. When possible rotation of the gas and emission from discrete sources are included flattened mass distributions are still required, although the constraints on \epsilon_{mass}$, but not the total mass, are substantially weakened.Comment: 45 pages (figures missing), PostScript, to appear in ApJ on January 20, 199

Metastable supersymmetry breaking in N=2 non-linear sigma-models

We perform a general study of the issue of metastability for supersymmetry-breaking vacua in theories with N=1 and N=2 global supersymmetry. This problem turns out to capture all the important qualitative features of the corresponding question in theories with local supersymmetry, where gravitational effects induce only quantitative modifications. Moreover, it allows to directly compare the conditions arising in the N=1 and N=2 cases, since the latter becomes particular case of the former in the rigid limit. Our strategy consists in a systematic investigation of the danger of instability coming from the sGoldstini scalars, whose masses are entirely due to supersymmetry breaking mass-splitting effects. We start by reviewing the metastability conditions arising in general N=1 non-linear sigma-models with chiral and vector multiplets. We then turn to the case of general N=2 non-linear sigma-models with hyper and vector multiplets. We first reproduce and clarify the known no-go theorems applying to theories with only Abelian vector multiplets and only hyper multiplets, and then derive new results applying to more general cases. To make the comparison with N=1 models as clear as possible, we rely on a formulation of N=2 models where one of the supersymmetries is manifestly realized in terms of ordinary superfields, whereas the other is realized through non-trivial transformations. We give a self-contained account of such a construction of N=2 theories in N=1 superspace, generalizing previous work on various aspects to reach a general and coordinate-covariant construction. We also present a direct computation of the supertrace of the mass matrix.Comment: 50 pages, no figures; v2 minor corrections and addition of comments and reference

Search for Conical Emission with Three-Particle Correlations

We present preliminary STAR results on 3-particle azimuthal angle correlation studies in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The studies are carried out at mid-rapidity between a trigger particle with 3 $\le p_{\perp} \le$ 4 GeV/c and two associated particles in 1 $\le p_{\perp} \le$ 2 GeV/c. A cumulant analysis reveals finite 3-particle azimuthal correlations, dominated by near and away side particle correlations consistent with jet production, and jet-flow correlations. We use a two-component model to remove underlying background correlations. This analysis indicates the presence of the conical emission signals in central Au+Au collisions within the model assumptions about background composition and normalization.Comment: Proceedings for STAR talk presented at Quark Matter 2006, 4 pages 2 figures, Version 2: typos corrected, references adde

Hunting in times of change: Uncovering indigenous strategies in the Colombian amazon using a role-playing game

Despite growing industrialization, the shift to a cash economy and natural resource overexploitation, indigenous people of the Amazon region hunt and trade wildlife in order to meet their livelihood requirements. Individual strategies, shaped by the hunters' values and expectations, are changing in response to the region's economic development, but they still face the contrasting challenges of poverty and overhunting. For conservation initiatives to be implemented effectively, it is crucial to take into account people's strategies with their underlying drivers and their adaptive capabilities within a transforming socio-economic environment. To uncover hunting strategies in the Colombian Amazon and their evolution under the current transition, we co-designed a role-playing game together with the local stakeholders. The game revolves around the tension between ecological sustainability and food security—hunters' current main concern. It simulates the mosaic of activities that indigenous people perform in the wet and dry season, while also allowing for specific hunting strategies. Socio-economic conditions change while the game unfolds, opening up to emerging alternative potential scenarios suggested by the stakeholders themselves. Do hunters give up hunting when given the opportunity of an alternative income and protein source? Do institutional changes affect their livelihoods? We played the game between October and December 2016 with 39 players—all of them hunters—from 9 different communities within the Ticoya reserve. Our results show that providing alternatives would decrease overall hunting effort, but impacts are not spatially homogenous. Legalizing trade could lead to overhunting except when market rules and competition come into place. When it comes to coupled human-nature systems, the best way forward to produce socially just and resilient conservation strategies might be to trigger an adaptive process of experiential learning and scenario exploration. The use of games as “boundary objects” can guide stakeholders through the process, eliciting the plurality of their strategies, their drivers and how outside change affects them

Age differences in fMRI adaptation for sound identity and location

We explored age differences in auditory perception by measuring fMRI adaptation of brain activity to repetitions of sound identity (what) and location (where), using meaningful environmental sounds. In one condition, both sound identity and location were repeated allowing us to assess non-specific adaptation. In other conditions, only one feature was repeated (identity or location) to assess domain-specific adaptation. Both young and older adults showed comparable non-specific adaptation (identity and location) in bilateral temporal lobes, medial parietal cortex, and subcortical regions. However, older adults showed reduced domain-specific adaptation to location repetitions in a distributed set of regions, including frontal and parietal areas, and to identity repetition in anterior temporal cortex. We also re-analyzed data from a previously published 1-back fMRI study, in which participants responded to infrequent repetition of the identity or location of meaningful sounds. This analysis revealed age differences in domain-specific adaptation in a set of brain regions that overlapped substantially with those identified in the adaptation experiment. This converging evidence of reductions in the degree of auditory fMRI adaptation in older adults suggests that the processing of specific auditory “what” and “where” information is altered with age, which may influence cognitive functions that depend on this processing