123,627 research outputs found
Discovery of a Kiloparsec Scale X-ray/Radio Jet in the z=4.72 Quasar GB 1428+4217
We report the discovery of a one-sided 3.6" (24 kpc, projected) long jet in
the high-redshift, z=4.72, quasar GB 1428+4217 in new Chandra X-ray and VLA
radio observations. This is the highest redshift kiloparsec-scale X-ray/radio
jet known. Analysis of archival VLBI 2.3 and 8.6 GHz data reveal a faint
one-sided jet extending out to ~200 parsecs and aligned to within ~30 deg of
the Chandra/VLA emission. The 3.6" distant knot is not detected in an archival
HST image, and its broad-band spectral energy distribution is consistent with
an origin from inverse Compton scattering of cosmic microwave background
photons for the X-rays. Assuming also equipartition between the radiating
particles and magnetic field, the implied jet Lorentz factor is ~5. This is
similar to the other two known z ~ 4 kpc-scale X-ray jet cases and smaller than
typically inferred in lower-redshift cases. Although there are still but a few
such very high-redshift quasar X-ray jets known, for an inverse Compton origin,
the present data suggest that they are less relativistic on large-scales than
their lower-redshift counterparts.Comment: ApJL, accepted, 5 pages, 3 figure
A note on Charmed and Bottomed Pentaquark Production by Fragmentation
H1 Collaboration recently observed the charmed pentaquark. In this short
note, we point out that the dominant production mechanism for pentaquark
consisting of a heavy quark is heavy quark fragmentation. We obtain a crude
estimate on the fragmentation probability for charm quark into Theta_c^0, based
on the known fragmentation probabilities of charm quark into mesons and
baryons: f(c-bar --> Theta_c^0) =~ (2-7) x 10^{-3}. Similarly, we also obtain
the fragmentation probability for bottom quark into Theta_b^+: f(b-bar -->
Theta_b^+) =~ (5-20) x 10^{-3}. We also estimate the prospect of observing
Theta_c^0 and Theta_b^+ at HERA, LEP, and Tevatron.Comment: RevTex, 4 pages, no figures, references adde
Culturally responsive teacher actions to support PÄsifika students in mathematical discourse : a thesis presented in partial fulfilment of the requirements for the degree of Master of Education at Massey University, Palmerston North, New Zealand
This study examines culturally responsive teaching to support a group of PÄsifika students aged 11-13 years old in mathematical discourse. It builds on previous work which has advocated culturally responsive practices where students learn mathematics through collaborative interaction that fosters greater student participation, engagement, and potentially better achievement in mathematics. In this study, the teacherâs actions drew on PÄsifika cultural practices and the value of the family, respect, and collectivism. This was significant in the establishment of social and mathematical behaviours which were important in supporting the development of productive mathematical discourse. In addition, the communicative and participation structures within the classroom that lead to mathematics learning are also considered.
This study was situated in an inquiry classroom. A socio-cultural perspective provided the framework for analysing the classroom context. A case study approach drawing on a qualitative design was implemented. Data was collected through teacher and student interviews, classroom audio and video-recorded observations, and studentsâ written work. Detailed retrospective analysis of the data was undertaken to develop the findings of this classroom case study.
Significant changes were revealed in the shifts of student discourse from long silences and hesitation to asking valid questions and developing mathematical justification with appropriate language and specific terms. The explicit instructional practices developed and implemented by the teacher fostered greater collaborative communication and interaction between group members and this was important in how they made mathematical meaning. The findings provide insights into the multi-dimensional ways that teachers can draw on studentsâ cultural strengths, values, and practices as invaluable resources which potentially will make a difference in studentsâ mathematical learning
Chiral differential operators on supermanifolds
The first part of this paper provides a new formulation of chiral
differential operators (CDOs) in terms of global geometric quantities. The main
result is a recipe to define all sheaves of CDOs on a smooth cs-manifold; its
ingredients consist of an affine connection and an even 3-form that trivializes
the first Pontrjagin form. With the connection fixed, two suitable 3-forms
define isomorphic sheaves of CDOs if and only if their difference is exact.
Moreover, conformal structures are in one-to-one correspondence with even
1-forms that trivialize the first Chern form.
Applying our work in the first part, we construct what may be called "chiral
Dolbeault complexes" of a complex manifold M, and analyze conditions under
which these differential vertex superalgebras admit compatible conformal
structures or extra gradings (fermion numbers). When M is compact, their
cohomology computes (in various cases) the Witten genus, the two-variable
elliptic genus and a spin-c version of the Witten genus. This part contains
some new results as well as provides a geometric formulation of certain known
facts from the study of holomorphic CDOs and sigma models.Comment: much simplified calculations in section 3, making full use of the
formulation from section 2; improved notation
Muon-proton Colliders: Leptoquarks, Contact Interactions and Extra Dimensions
We discuss the physics potential of the collider; especially,
leptoquarks, leptogluons, R-parity violating squarks, contact interactions, and
large extra dimensions. We calculate the sensitivity reach for these new
physics at colliders of various energies and luminosities.Comment: 8 pages. Talk at the MuMu99, San Francisco C
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