3,805 research outputs found
A Portalino to the Dark Sector
"Portal" models that connect the Standard Model to a Dark Sector allow for a
wide variety of scenarios beyond the simplest WIMP models. Kinetic mixing of
gauge fields in particular has allowed a broad range of new ideas. However, the
models that evade CMB constraints are often non-generic, with new mass scales
and operators to split states and suppress indirect detection signals. Models
with a "portalino", a neutral fermion that marries a linear combination of a
standard model neutrino and dark sector fermion and carries a conserved quantum
number, can be simpler. This is especially interesting for interacting dark
sectors; then the unmarried linear combination which we identify as the
standard model neutrino inherits these interactions too, and provides a new,
effective interaction between the dark sector and the standard model. These
interactions can be simple type interactions or lepton-flavor changing.
Dark matter freezes out into neutrinos, thereby evading CMB constraints, and
conventional direct detection signals are largely absent. The model offers
different signals, however. The "portalino" mechanism itself predicts small
corrections to the standard model neutrino couplings as well as the possibility
of discovering the portalino particle in collider experiments. Possible
cosmological and astroparticle signatures include monochromatic neutrino
signals from annihilation, spectral features in high energy CR neutrinos as
well as conventional signals of additional light species and dark matter
interactions.Comment: v2 - minor changes, references adde
Convicted Murderers and the Victorian Press: Condemnation vs. Sympathy
Almost half of those receiving the death sentence in late-Victorian and Edwardian England were reprieved. The process of deciding which murderers were to hang and which were to be spared became an increasingly public one, thanks to the growing intervention of the press. This intervention grew alongside the accelerated expansion in the numbers and circulations of newspapers in the second half of the nineteenth century. As the press became a larger part of national life, its more 'popular' and its more local segments carved out for themselves a new and ever more prominent role as major participants in public discourse over 'justice' vs. 'mercy' for condemned murderers. This involvement is a facet of Victorian and Edwardian newspapers that has previously been overlooked. "I always ask to see the local newspaper reports in capital cases." Sir William Harcourt, Home Secretary 1882
Transient behavior of surface plasmon polaritons scattered at a subwavelength groove
We present a numerical study and analytical model of the optical near-field
diffracted in the vicinity of subwavelength grooves milled in silver surfaces.
The Green's tensor approach permits computation of the phase and amplitude
dependence of the diffracted wave as a function of the groove geometry. It is
shown that the field diffracted along the interface by the groove is equivalent
to replacing the groove by an oscillating dipolar line source. An analytic
expression is derived from the Green's function formalism, that reproduces well
the asymptotic surface plasmon polariton (SPP) wave as well as the transient
surface wave in the near-zone close to the groove. The agreement between this
model and the full simulation is very good, showing that the transient
"near-zone" regime does not depend on the precise shape of the groove. Finally,
it is shown that a composite diffractive evanescent wave model that includes
the asymptotic SPP can describe the wavelength evolution in this transient
near-zone. Such a semi-analytical model may be useful for the design and
optimization of more elaborate photonic circuits whose behavior in large part
will be controlled by surface waves.Comment: 12 pages, 10 figure
USER-DESIGNED SOFTWARE AS A SERVICE – CAN CONCEPTUAL WORK BE SHIFTED TO THE END-USER
Cloud Computing and especially Software as a Service (SaaS) is predicted to bring about the next information technology(IT) revolution. Benefits and risks have been discussed extensively in both research and practice. Key benefits like higherflexibility and lower costs are confronted with major risks such as loss of data control. These benefits and risks arepredominantly discussed in the context of traditional SaaS. Here, the administrator configures and maintains the application.In contrast, new SaaS concepts allow shifting conceptual work to end-users by enabling them to adjust standard SaaSsoftware independently from their IT department. Using an action research approach, we investigated the benefits and risks ofthis so called user-designed SaaS, and compared them to those of traditional, administrator-designed SaaS. Many benefitsand risks still apply to user-designed SaaS, but also so far unknown benefits like higher user acceptance and lowerdependency to administrators, as well as new risks like shifting conceptual skills to the end-user were observed
Competence Based IT Outsourcing - An Evaluation of Models for Identifying and Analyzing Core Competences
In an effort to re-focus on their core competences, an increasing number of companies outsource parts of their IT services. In this context, based on Hamel and Prahalad’s definition of core competences, numerous theoretical models for identifying and analyzing core competences were developed. However, at present, due to the high complexity of outsourcing decisions, it is not clear which theoretical models can support decision-makers and to what extent these models can make a contribution. To address these questions, theoretical models for identifying and analyzing core competences, suitable for supporting IT outsourcing decisions in general, are identified, and systematically classified within a framework. Based on the developed classification, one model of each model category is evaluated on the basis of a list of six criteria
The Persistence of Cool Galactic Winds in High Stellar Mass Galaxies Between z~1.4 and ~1
We present an analysis of the MgII 2796, 2803 and FeII 2586, 2600 absorption
line profiles in coadded spectra of 468 galaxies at 0.7 < z < 1.5. The galaxy
sample, drawn from the Team Keck Treasury Redshift Survey of the GOODS-N field,
has a range in stellar mass (M_*) comparable to that of the sample at z~1.4
analyzed in a similar manner by Weiner et al. (2009; W09), but extends to lower
redshifts and has specific star formation rates which are lower by ~0.6 dex. We
identify outflows of cool gas from the Doppler shift of the MgII absorption
lines and find that the equivalent width (EW) of absorption due to outflowing
gas increases on average with M_* and star formation rate (SFR). We attribute
the large EWs measured in spectra of the more massive, higher-SFR galaxies to
optically thick absorbing clouds having large velocity widths. The outflows
have hydrogen column densities N(H) > 10^19.3 cm^-2, and extend to velocities
of ~500 km/s. While galaxies with SFR > 10 Msun/yr host strong outflows in both
this and the W09 sample, we do not detect outflows in lower-SFR (i.e., log
M_*/Msun < 10.5) galaxies at lower redshifts. Using a simple galaxy evolution
model which assumes exponentially declining SFRs, we infer that strong outflows
persist in galaxies with log M_*/Msun > 10.5 as they age between z=1.4 and z~1,
presumably because of their high absolute SFRs. Finally, using high resolution
HST/ACS imaging in tandem with our spectral analysis, we find evidence for a
weak trend (at 1 sigma significance) of increasing outflow absorption strength
with increasing galaxy SFR surface density.Comment: Submitted to ApJ. 25 pages, 19 figures, Figure 2 reduced in
resolution. Uses emulateapj forma
Magic numbers in polymer phase separation -- the importance of being rigid
Cells possess non-membrane-bound bodies, many of which are now understood as
phase-separated condensates. One class of such condensates is composed of two
polymer species, where each consists of repeated binding sites that interact in
a one-to-one fashion with the binding sites of the other polymer. Previous
biologically-motivated modeling of such a two-component system surprisingly
revealed that phase separation is suppressed for certain combinations of
numbers of binding sites. This phenomenon, dubbed the "magic-number effect",
occurs if the two polymers can form fully-bonded small oligomers by virtue of
the number of binding sites in one polymer being an integer multiple of the
number of binding sites of the other. Here we use lattice-model simulations and
analytical calculations to show that this magic-number effect can be greatly
enhanced if one of the polymer species has a rigid shape that allows for
multiple distinct bonding conformations. Moreover, if one species is rigid, the
effect is robust over a much greater range of relative concentrations of the
two species. Our findings advance our understanding of the fundamental physics
of two-component polymer-based phase-separation and suggest implications for
biological and synthetic systems.Comment: 8 pages + 15 pages S
Fine-Structure FeII* Emission and Resonant MgII Emission in z = 1 Star-Forming Galaxies
We present a study of the prevalence, strength, and kinematics of ultraviolet
FeII and MgII emission lines in 212 star-forming galaxies at z = 1 selected
from the DEEP2 survey. We find FeII* emission in composite spectra assembled on
the basis of different galaxy properties, indicating that FeII* emission is
prevalent at z = 1. In these composites, FeII* emission is observed at roughly
the systemic velocity. At z = 1, we find that the strength of FeII* emission is
most strongly modulated by dust attenuation, and is additionally correlated
with redshift, star-formation rate, and [OII] equivalent width, such that
systems at higher redshifts with lower dust levels, lower star-formation rates,
and larger [OII] equivalent widths show stronger FeII* emission. We detect MgII
emission in at least 15% of the individual spectra and we find that objects
showing stronger MgII emission have higher specific star-formation rates,
smaller [OII] linewidths, larger [OII] equivalent widths, lower dust
attenuations, and lower stellar masses than the sample as a whole. MgII
emission strength exhibits the strongest correlation with specific
star-formation rate, although we find evidence that dust attenuation and
stellar mass also play roles in the regulation of MgII emission. Future
integral field unit observations of the spatial extent of FeII* and MgII
emission in galaxies with high specific star-formation rates, low dust
attenuations, and low stellar masses will be important for probing the
morphology of circumgalactic gas.Comment: 29 pages, 22 figures, 2 tables; accepted to Ap
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