238 research outputs found
PAMELA/ATIC Anomaly from Exotic Mediated Dark Matter Decay
We discuss dark matter decay mediated by exotically charged particles
("exotics") in a supersymmetric model with two dark matter (DM) components: One
is the (bino-like) lightest supersymmetric particle (LSP) \chi, and the other
is a newly introduced meta-stable neutral singlet . decays to \chi
e^+e^- via a dimension 6 operator induced by a penguin-type one loop diagram
with the life time of 10^{26} sec., explaining energetic cosmic e^\pm excess
observed recently by PAMELA and ATIC/PPB-BETS. The superheavy masses of exotics
(\sim 10^{15-16} GeV) are responsible for the longevity of . The
superpartner of develops the vacuum expectation value (VEV) of order TeV so
that the DM achieves the desired mass of 2 TeV. By the VEV, the U(1)_R
symmetry is broken to the discrete Z_2 symmetry, which is identified with the
matter parity in the minimal supersymmetric standard model (MSSM). Since we
have the two DM components, even extremely small amount of [O(10^{-10}) <
(n_N/n_\chi)] could account for the observed positron flux with relatively
light exotics' masses [10^{12} GeV < M_{exo.} < 10^{16} GeV].Comment: 1+7 pages, version to appear in JHE
A complete 3D numerical study of the effects of pseudoscalar-photon mixing on quasar polarizations
We present the results of three-dimensional simulations of quasar
polarizations in the presence of pseudoscalar-photon mixing in the
intergalactic medium. The intergalactic magnetic field is assumed to be
uncorrelated in wave vector space but correlated in real space. Such a field
may be obtained if its origin is primordial. Furthermore we assume that the
quasars, located at cosmological distances, have negligible initial
polarization. In the presence of pseudoscalar-photon mixing we show, through a
direct comparison with observations, that this may explain the observed large
scale alignments in quasar polarizations within the framework of big bang
cosmology. We find that the simulation results give a reasonably good fit to
the observed data.Comment: 15 pages, 8 figures, significant changes, to appear in EPJ
PAMELA/ATIC anomaly from the meta-stable extra dark matter component and the leptophilic Yukawa interaction
We present a supersymmetric model with two dark matter (DM) components
explaining the galactic positron excess observed by PAMELA/HEAT and
ATIC/PPB-BETS: One is the conventional (bino-like) lightest supersymmetric
particle (LSP) \chi, and the other is a TeV scale meta-stable neutral singlet
N_D, which is a Dirac fermion (N,N^c). In this model, N_D decays dominantly
into \chi e^+e^- through an R parity preserving dimension 6 operator with the
life time \tau_N\sim 10^{26} sec. We introduce a pair of vector-like superheavy
SU(2) lepton doublets (L,L^c) and lepton singlets (E,E^c). The dimension 6
operator leading to the N_D decay is generated from the leptophilic Yukawa
interactions by W\supset Ne^cE+Lh_dE^c+m_{3/2}l_1L^c with the dimensionless
couplings of order unity, and the gauge interaction by {\cal L}\supset \sqrt{2}
g'\tilde{e}^{c*}e^c\chi + h.c. The superheavy masses of the vector-like leptons
(M_L, M_E\sim 10^{16} GeV) are responsible for the longevity of N_D. The low
energy field spectrum in this model is just the MSSM fields and N_D. Even for
the case that the portion of N_D is much smaller than that of \chi in the total
DM density [{\cal O}(10^{-10}) \lesssim n_{N_D}/n_\chi], the observed positron
excess can be explained by adopting relatively lighter masses of the
vector-like leptons (10^{13} GeV \lesssim M_{L,E} \lesssim 10^{16} GeV). The
smallness of the electron mass is also explained. This model is easily embedded
in the flipped SU(5) grand unification, which is a leptophilic unified theory.Comment: 12 pages, published versio
SQuIGGLE: studying quenching in intermediate-z galaxies- gas, anguLar momentum, and evolution
Galaxie
Erratum: SQuIGGLE: studying quenching in intermediate-z galaxies: gas, AnguLar momentum, and evolution
This is a correction for 2022 ApJ 926 89DOI 10.3847/1538-4357/ac404aGalaxie
Size Doesn't Matter: Towards a More Inclusive Philosophy of Biology
notes: As the primary author, O’Malley drafted the paper, and gathered and analysed data (scientific papers and talks). Conceptual analysis was conducted by both authors.publication-status: Publishedtypes: ArticlePhilosophers of biology, along with everyone else, generally perceive life to fall into two broad categories, the microbes and macrobes, and then pay most of their attention to the latter. ‘Macrobe’ is the word we propose for larger life forms, and we use it as part of an argument for microbial equality. We suggest that taking more notice of microbes – the dominant life form on the planet, both now and throughout evolutionary history – will transform some of the philosophy of biology’s standard ideas on ontology, evolution, taxonomy and biodiversity. We set out a number of recent developments in microbiology – including biofilm formation, chemotaxis, quorum sensing and gene transfer – that highlight microbial capacities for cooperation and communication and break down conventional thinking that microbes are solely or primarily single-celled organisms. These insights also bring new perspectives to the levels of selection debate, as well as to discussions of the evolution and nature of multicellularity, and to neo-Darwinian understandings of evolutionary mechanisms. We show how these revisions lead to further complications for microbial classification and the philosophies of systematics and biodiversity. Incorporating microbial insights into the philosophy of biology will challenge many of its assumptions, but also give greater scope and depth to its investigations
New insights into the genetic etiology of Alzheimer's disease and related dementias
Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele
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