976 research outputs found
Semi-direct Gauge Mediation in Conformal Windows of Vector-like Gauge Theories
Direct gauge mediation models using the Intriligator-Seiberg-Shih (ISS)
metastable vacua suffer from the Landau pole problem of the standard model
gauge couplings and the existence of R symmetry forbidding gaugino masses.
These problems may be solved by using the recently proposed SUSY breaking
models in a conformal window of the vector-like gauge theory with
gauge singlets. In this paper we propose a model of gauge mediation based on
the SUSY-breaking model in the conformal window, and study the dynamics for the
SUSY breaking. In the model, there are massive vector-like bifundamental fields
charged under both and the standard model gauge group, and our model
can be regarded as a semi-direct gauge mediation model. The color number
can be small to avoid the Landau pole problem, and the R symmetry is also
broken under a reasonable assumption on the strong dynamics of the model. The
model possesses only one free parameter, and the gaugino and sfermion masses
are naturally of the same order.Comment: 21 pages, 1 figur
Relaxing a constraint on the number of messengers in a low-scale gauge mediation
We propose a mechanism for relaxing a constraint on the number of messengers
in low-scale gauge mediation models. The Landau pole problem for the
standard-model gauge coupling constants in the low-scale gauge mediation can be
circumvented by using our mechanism. An essential ingredient is a large
positive anomalous dimension of messenger fields given by a large Yukawa
coupling in a conformal field theory at high energies. The positive anomalous
dimension reduces the contribution of the messengers to the beta function of
the standard-model gauge couplings.Comment: 22pages; v2:explanations expanded in sec.3.2, reference adde
Ecological damage, human rights and Oil: local advocacy NGOs dialogic action and alternative accounting practices
This study explores why local NGOs in the Niger Delta integrate dialogic action and accounts into their campaigns to protect the human, economic and environmental rights of indigenous communities. The NGOs considered their alternative-accounts effective in problematizing the need for greater accountability, giving greater visibilities to unsustainable practices, building the capacity of the indigenous people, creating networks of engagement, giving voice to indigenous communities and addressing some of the power imbalances in this region. NGOs and local community representatives asserted that the production and communication of accounts of their suffering were making a difference and creating hope for future change
ENSO Effect on East Asian Tropical Cyclone Landfall via Changes in Tracks and Genesis in a Statistical Model
Improvements on a statistical tropical cyclone (TC) track model in the western North Pacific Ocean are described. The goal of the model is to study the effect of El Nino-Southern Oscillation (ENSO) on East Asian TC landfall. The model is based on the International Best-Track Archive for Climate Stewardship (IBTrACS) database of TC observations for 1945-2007 and employs local regression of TC formation rates and track increments on the Nino-3.4 index and seasonally varying climate parameters. The main improvements are the inclusion of ENSO dependence in the track propagation and accounting for seasonality in both genesis and tracks. A comparison of simulations of the 1945-2007 period with observations concludes that the model updates improve the skill of this model in simulating TCs. Changes in TC genesis and tracks are analyzed separately and cumulatively in simulations of stationary extreme ENSO states. ENSO effects on regional (100-km scale) landfall are attributed to changes in genesis and tracks. The effect of ENSO on genesis is predominantly a shift in genesis location from the southeast in El Nino years to the northwest in La Nina years, resulting in higher landfall rates for the East Asian coast during La Nina. The effect of ENSO on track propagation varies seasonally and spatially. In the peak activity season (July-October), there are significant changes in mean tracks with ENSO. Landfall-rate changes from genesis- and track-ENSO effects in the Philippines cancel out, while coastal segments of Vietnam, China, the Korean Peninsula, and Japan show enhanced La Nina-year increases
On the Trace Anomaly and the Anomaly Puzzle in N=1 Pure Yang-Mills
The trace anomaly of the energy-momentum tensor is usually quoted in the form
which is proportional to the beta function of the theory. However, there are in
general many definitions of gauge couplings depending on renormalization
schemes, and hence many beta functions. In particular, N=1 supersymmetric pure
Yang-Mills has the holomorphic gauge coupling whose beta function is one-loop
exact, and the canonical gauge coupling whose beta function is given by the
Novikov-Shifman-Vainshtein-Zakharov beta function. In this paper, we study
which beta function should appear in the trace anomaly in N=1 pure Yang-Mills.
We calculate the trace anomaly by employing the N=4 regularization of N=1 pure
Yang-Mills. It is shown that the trace anomaly is given by one-loop exact form
if the composite operator appearing in the trace anomaly is renormalized in a
preferred way. This result gives the simplest resolution to the anomaly puzzle
in N=1 pure Yang-Mills. The most important point is to examine in which scheme
the quantum action principle is valid, which is crucial in the derivation of
the trace anomaly.Comment: 25 pages, 1 figure; v2:slight correction in sec.5, minor addition in
appendi
Extending the limits of globule detection -- ISOPHOT Serendipity Survey Observations of interstellar clouds
A faint MJysr bipolar globule was discovered with the
ISOPHOT 170 m Serendipity Survey (ISOSS). ISOSS J 20246+6541 is a cold
( K) FIR source without an IRAS pointsource counterpart.
In the Digitized Sky Survey B band it is seen as a 3\arcmin size bipolar
nebulosity with an average excess surface brightness of
mag/\arcsec . The CO column density distribution determined by
multi-isotopic, multi-level CO measurements with the IRAM-30m telescope agrees
well with the optical appearance. An average hydrogen column density of
cm was derived from both the FIR and CO data. Using a
kinematic distance estimate of 400 pc the NLTE modelling of the CO, HCO,
and CS measurements gives a peak density of cm. The
multiwavelength data characterise ISOSS 20246+6541 as a representative of a
class of globules which has not been discovered so far due to their small
angular size and low 100m brightness. A significant overabundance of
CO is found . This is likely due to
isotope selective chemical processes.Comment: 5 pages, 3 figure
Modelling of the multi-transition periodic flaring in G9.62+0.20E
We present detailed modeling of periodic flaring events in the 6.7 GHz and
12.2 GHz methanol lines as well as the OH 1665 MHz and 1667 MHz transitions
observed in the G9.62+0.20E star-forming region. Our analysis is performed
within the framework of the one-dimensional Maxwell-Bloch equations, which
intrinsically cover the complementary quasi-steady state maser and transient
superradiance regimes. We find that the variations in flaring time-scales
measured for the different species/transitions, and sometimes even for a single
spectral line, are manifestations of and are best modeled with Dicke's
superradiance, which naturally accounts for a modulation in the duration of
flares through corresponding changes in the inversion pump. In particular, it
can explain the peculiar behaviour observed for some features, such as the
previously published result for the OH 1667 MHz transition at
km s as well as the methanol 6.7 GHz line at
km s, through a partial quenching of the
population inversion during flaring events.Comment: 13 pages, 13 figures, accepted MNRA
Probing the structure of a birthplace of intermediate-mass stars: Ammonia cores in Lynds 1340
Lynds 1340, a molecular cloud forming intermediate-mass stars, has been
mapped in the NH_3(1,1) and (2,2) transitions with the Effelsberg 100m
telescope. We observed the whole area of the cloud where C18O emission was
detected earlier, at a 40 arcsec grid, with additional positions towards the
C18O peaks and optically invisible IRAS point sources. Our observations covered
an area of 170 arcmin^2, corresponding to about 5.15 pc^2 at a distance of 600
pc, and revealed 10 ammonia cores. The cores, occupying some 7% of the mapped
area, probably represent the highest density regions of L1340. Their total mass
is 80 solar mass, about 6% of the mass traced by C18O. Six cores are associated
with optically invisible IRAS point sources. Their average nonthermal line
width is 0.78 kms^{-1}, while the same quantity for the four starless cores is
0.28 kms^{-1}. We suggest that the narrow-line cores are destined to form
low-mass stars, whereas small groups of intermediate-mass stars are being
formed in the turbulent cores. The features traced by NH_3, 13CO, C18O and HI
obey the line width-size relation log Delta v_{NT} = 0.41(0.06)log R_{1/2}+
0.12(0.06). Comparison of sizes, densities and nonthermal line widths of
ammonia cores with those of C18O and 13CO structures supports the scenario in
which core formation has been induced by turbulent fragmentation. The typical
physical properties of the ammonia cores of L1340, R_{1/2} =0.08 pc,
T_{kin}=13.8 K, Delta v_{total}=0.64 kms^{-1}, and M =9 solar mass are close to
those of the high-mass star forming Perseus and Orion B clouds.Comment: 13 pages, 11 figures. Accepted by A&
Discovery of Large-Scale Gravitational Infall in a Massive Protostellar Cluster
We report Mopra (ATNF), Anglo-Australian Telescope, and Atacama Submillimeter
Telescope Experiment observations of a molecular clump in Carina, BYF73 =
G286.21+0.17, which give evidence of large-scale gravitational infall in the
dense gas. From the millimetre and far-infrared data, the clump has mass ~ 2 x
10^4 Msun, luminosity ~ 2-3 x 10^4 Lsun, and diameter ~ 0.9 pc. From radiative
transfer modelling, we derive a mass infall rate ~ 3.4 x 10^-2 Msun yr-1. If
confirmed, this rate for gravitational infall in a molecular core or clump may
be the highest yet seen. The near-infrared K-band imaging shows an adjacent
compact HII region and IR cluster surrounded by a shell-like photodissociation
region showing H2 emission. At the molecular infall peak, the K imaging also
reveals a deeply embedded group of stars with associated H2 emission. The
combination of these features is very unusual and we suggest they indicate the
ongoing formation of a massive star cluster. We discuss the implications of
these data for competing theories of massive star formation.Comment: v1: 23 pages single-column, 6 figures (some multipart) at end v2: 14
pages 2-column, 6 figures interspersed v3: edited to referee's comments with
new sections and new figures; accepted to MNRAS, 20 pages 2-column, 8 figures
(some multipart) intersperse
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