274 research outputs found
The Minimal Model for Dark Matter and Unification
Gauge coupling unification and the success of TeV-scale weakly interacting
dark matter are usually taken as evidence of low energy supersymmetry (SUSY).
However, if we assume that the tuning of the higgs can be explained in some
unnatural way, from environmental considerations for example, SUSY is no longer
a necessary component of any Beyond the Standard Model theory. In this paper we
study the minimal model with a dark matter candidate and gauge coupling
unification. This consists of the SM plus fermions with the quantum numbers of
SUSY higgsinos, and a singlet. It predicts thermal dark matter with a mass that
can range from 100 GeV to around 2 TeV and generically gives rise to an
electric dipole moment that is just beyond current experimental limits, with a
large portion of its allowed parameter space accessible to next generation EDM
and direct detection experiments. We study precision unification in this model
by embedding it in a 5-D orbifold GUT where certain large threshold corrections
are calculable, achieving gauge coupling and b-tau unification, and predicting
a rate of proton decay just beyond current limits.Comment: 20 pages, 10 figures. v2: Minor typos and Reference errors corrected.
Modified explanation of the KK mode contribution to runnin
Spinless photon dark matter from two universal extra dimensions
We explore the properties of dark matter in theories with two universal extra
dimensions, where the lightest Kaluza-Klein state is a spin-0 neutral particle,
representing a six-dimensional photon polarized along the extra dimensions.
Annihilation of this 'spinless photon' proceeds predominantly through Higgs
boson exchange, and is largely independent of other Kaluza-Klein particles. The
measured relic abundance sets an upper limit on the spinless photon mass of 500
GeV, which decreases to almost 200 GeV if the Higgs boson is light. The
phenomenology of this dark matter candidate is strikingly different from
Kaluza-Klein dark matter in theories with one universal extra dimension.
Elastic scattering of the spinless photon with quarks is helicity suppressed,
making its direct detection challenging, although possible at upcoming
experiments. The prospects for indirect detection with gamma rays and
antimatter are similar to those of neutralinos. The rates predicted at neutrino
telescopes are below the sensitivity of next-generation experiments.Comment: 22 pages. Figure 7 corrected, leading to improved prospects for
direct detection. Some clarifying remarks include
Outside interference or Hong Kong embracing its unique identity? : The Chinese Universities Shakespeare Festival
Ongoing clashes between Hong Kong citizens and its government have foregrounded questions about outside interference in Hong Kong’s politics (largely from the government and media of People’s Public of China), as well as debate about what institutions in Hong Kong are neo-colonial, heavily inflected with nostalgia for British colonialism, or in the process of being ‘colonised’ by the People’s Republic of China. This article looks at Shakespeare in Hong Kong (and, to some extent, greater Chinese) theatre and education as one of those contested institutions, using the particular case of the now-defunct Chinese Universities Shakespeare Festival. The author probes their initial, surface impression of the festival as a simple outpouring of colonial sentiment and impulse, using its sizeable archives to realise a reading of the institution that highlights the complexities of international and intra-regional politics, culture and identity in Hong Kong and greater China. It builds on the Hong Kong literary critic Michael Ingham’s call for attention to Hong Kong’s quest – sometimes overt (as in the demonstrations of 2019), sometimes implicit (in the body of literature Ingham explores in his cultural and literary history) – for a unique, post-colonial identity that is inspired – but, critically, not confined – by its Chinese and British histories. The article briefly outlines the origins and set-up of the festival before juxtaposing the dominance of English language and culture in it with the opportunities it presents (seized by several teams) for intra-regional cooperation, competition and sharing diverse, greater Chinese cultures. The article offers a model for critically appraising other institutions and cultural products in Hong Kong in ways that resist easy binaries of British or Chinese, colonial or indigenous
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Engaging Cold to Upregulate Cell Proliferation in Alginate-Encapsulated Liver Spheroids.
For many years, the impact of hyper- and hypothermia on mammalian cells has been examined. With the exception of short, low temperature storage, which has uses in areas such as preservation for transplantation or regenerative medicine, advantages for the use of low temperature treatment in hepatocytes have not been previously reported. We have observed that alginate-encapsulated HepG2 liver spheroids that are cryopreserved or experience a cold reduction in temperature (≤10°C) for periods between 1 and 90 min display an enhanced cell proliferation during culture 7-16 days post-treatment compared with untreated samples. Following 8-12 days post-treatment, alginate-encapsulated liver spheroids experienced a cell density of 1.71 ± 0.35 times that of control samples (p < 0.001). This effect occurred in samples with a variety of cold treatments. This low temperature treatment offers a simple method to rapidly increase cell proliferation rates for extended culture systems, such as bioartificial liver devices. This would allow the manufacture of required biomass more rapidly, and to a higher cell density, reducing final required biomass volume. This could enable bioartificial liver devices to be prepared more cheaply, making them a more cost effective treatment.Funding for this work was provided through a Medical Research Council (United Kingdom) Industrial Case Studentship (9203) and by Innovate UK (101103) between University College London and Asymptote Ltd. and a Medical Research Council Proximity to Discovery Grant (RG79366) between University of Cambridge and Asymptote Ltd
The New Fat Higgs: Slimmer and More Attractive
In this paper we increase the MSSM tree level higgs mass bound to a value
that is naturally larger than the LEP-II search constraint by adding to the
superpotential a term, as in the NMSSM, and UV
completing with new strong dynamics {\it before} becomes
non-perturbative. Unlike other models of this type the higgs fields remain
elementary, alleviating the supersymmetric fine-tuning problem while
maintaining unification in a natural way.Comment: 14 pages and 2 figures. Added references and updated argument about
constraints from reheating temperatur
East Asia and the global/transatlantic/Western crisis
This paper introduces the special collection on East Asia and the Global Crisis. After justifying why a focus on East Asia is appropriate, it draws out the main themes that run through the individual contributions. These are the extent to which the region is decoupling from the global economy (or the West), the increasing legitimacy of statist alternatives to neoliberal development strategies, and the impact of crises on the definition of ―region‖ and the functioning of regional institutions and governance mechanisms
Precision Electroweak Observables in the Minimal Moose Little Higgs Model
Little Higgs theories, in which the Higgs particle is realized as the
pseudo-Goldstone boson of an approximate global chiral symmetry have generated
much interest as possible alternatives to weak scale supersymmetry. In this
paper we analyze precision electroweak observables in the Minimal Moose model
and find that in order to be consistent with current experimental bounds, the
gauge structure of this theory needs to be modified. We then look for viable
regions of parameter space in the modified theory by calculating the various
contributions to the S and T parameters.Comment: v2: 17 pages, 9 figures. Typeset in JHEP style. Added a references
and two figures showing parameter space for each of two reference points.
Corrected typo
The Gran Sasso muon puzzle
We carry out a time-series analysis of the combined data from three
experiments measuring the cosmic muon flux at the Gran Sasso laboratory, at a
depth of 3800 m.w.e. These data, taken by the MACRO, LVD and Borexino
experiments, span a period of over 20 years, and correspond to muons with a
threshold energy, at sea level, of around 1.3 TeV. We compare the best-fit
period and phase of the full muon data set with the combined DAMA/NaI and
DAMA/LIBRA data, which spans the same time period, as a test of the hypothesis
that the cosmic ray muon flux is responsible for the annual modulation detected
by DAMA. We find in the muon data a large-amplitude fluctuation with a period
of around one year, and a phase that is incompatible with that of the DAMA
modulation at 5.2 sigmas. Aside from this annual variation, the muon data also
contains a further significant modulation with a period between 10 and 11 years
and a power well above the 99.9% C.L threshold for noise, whose phase
corresponds well with the solar cycle: a surprising observation for such high
energy muons. We see no corresponding long-period oscillation in the
stratospheric temperature data.Comment: Minor changes and clarifications, matches version accepted at JCAP. 5
pages, 3 figure
Neutrino Mass from R-parity Violation in Split Supersymmetry
We investigate how the observed neutrino data can be accommodated by R-parity
violation in Split Supersymmetry. The atmospheric neutrino mass and mixing are
explained by the bilinear parameters inducing the neutrino-neutralino
mixing as in the usual low-energy supersymmetry. Among various one-loop
corrections, only the quark-squark exchanging diagrams involving the order-one
trilinear couplings can generate the solar neutrino mass
and mixing if the scalar mass is not larger than GeV. This scheme
requires an unpleasant hierarchical structure of the couplings, e.g.,
, and . On the other hand, the model has a distinct collider
signature of the lightest neutralino which can decay only to the final states,
and , arising from the bilinear mixing. Thus, the
measurement of the ratio; would provide a clean probe of the small reactor and
large atmospheric neutrino mixing angles as far as the neutralino mass is
larger than 62 GeV.Comment: 10 pages, 3 figures, version submitted to JHE
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Isolation and propagation of primary human cholangiocyte organoids for the generation of bioengineered biliary tissue.
Pediatric liver transplantation is often required as a consequence of biliary disorders because of the lack of alternative treatments for repairing or replacing damaged bile ducts. To address the lack of availability of pediatric livers suitable for transplantation, we developed a protocol for generating bioengineered biliary tissue suitable for biliary reconstruction. Our platform allows the derivation of cholangiocyte organoids (COs) expressing key biliary markers and retaining functions of primary extra- or intrahepatic duct cholangiocytes within 2 weeks of isolation. COs are subsequently seeded on polyglycolic acid (PGA) scaffolds or densified collagen constructs for 4 weeks to generate bioengineered tissue retaining biliary characteristics. Expertise in organoid culture and tissue engineering is desirable for optimal results. COs correspond to mature functional cholangiocytes, differentiating our method from alternative organoid systems currently available that propagate adult stem cells. Consequently, COs provide a unique platform for studies in biliary physiology and pathophysiology, and the resulting bioengineered tissue has broad applications for regenerative medicine and cholangiopathies
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