13,754 research outputs found
Effects of Unstable Dark Matter on Large-Scale Structure and Constraints from Future Surveys
In this paper we explore the effect of decaying dark matter (DDM) on
large-scale structure and possible constraints from galaxy imaging surveys. DDM
models have been studied, in part, as a way to address apparent discrepancies
between the predictions of standard cold dark matter models and observations of
galactic structure. Our study is aimed at developing independent constraints on
these models. In such models, DDM decays into a less massive, stable dark
matter (SDM) particle and a significantly lighter particle. The small mass
splitting between the parent DDM and the daughter SDM provides the SDM with a
recoil or "kick" velocity vk, inducing a free-streaming suppression of matter
fluctuations. This suppression may be probed via weak lensing power spectra
measured by a number of forthcoming imaging surveys that aim primarily to
constrain dark energy. Using scales on which linear perturbation theory alone
is valid (multipoles < 300), surveys like Euclid or LSST can be sensitive to vk
> 90 km/s for lifetimes ~ 1-5 Gyr. To estimate more aggressive constraints, we
model nonlinear corrections to lensing power using a simple halo evolution
model that is in good agreement with numerical simulations. In our most
ambitious forecasts, using multipoles < 3000, we find that imaging surveys can
be sensitive to vk ~ 10 km/s for lifetimes < 10 Gyr. Lensing will provide a
particularly interesting complement to existing constraints in that they will
probe the long lifetime regime far better than contemporary techniques. A
caveat to these ambitious forecasts is that the evolution of perturbations on
nonlinear scales will need to be well calibrated by numerical simulations
before they can be realized. This work motivates the pursuit of such a
numerical simulation campaign to constrain dark matter with cosmological weak
lensing.Comment: 15 pages, 7 figures. Submitted to PR
Universal Thermoelectric Effect of Dirac Fermions in Graphene
We numerically study the thermoelectric transports of Dirac fermions in
graphene in the presence of a strong magnetic field and disorder. We find that
the thermoelectric transport coefficients demonstrate universal behavior
depending on the ratio between the temperature and the width of the
disorder-broadened Landau levels(LLs). The transverse thermoelectric
conductivity reaches a universal quantum value at the center of
each LL in the high temperature regime, and it has a linear temperature
dependence at low temperatures. The calculated Nernst signal has a peak at the
central LL with heights of the order of , and changes sign near other
LLs, while the thermopower has an opposite behavior, in good agreement with
experimental data. The validity of the generalized Mott relation between the
thermoelectric and electrical transport coefficients is verified in a wide
range of temperatures.Comment: 4 pages, 4 figures, published versio
Efktifitas Baby Solus Per Aqua (Spa) terhadap Peningkatan Berat Badan dengan Bayi Berat Badan Rendah Usia 7 Bulan
Pelayanan SPA merupakan bagian dari upaya pelayanan kesehatan tradisional yang sekaligus sebagai upaya pelestarian budaya/pusaka nusantara .Menurut penelitian yang dilakukan oleh ilmuan dan Institut Griffith For Educational Research 2007. Mereka menelliti orang tua dari 7000 anak di Astralia, Selandia Baru dan Amerika Serikat. Anak-anak yang dilibatkan dalam penelitian ini semuanya berusia di baah 1 tahun dan penelitian berlangsung selama 3 tahun. Profesor Robyn Jourgensen, yang memimpin penelitian itu mengatakan, anak-anak yang belajar berenang di usia dini memiliki banyak keterampilan dan mencapai titik pertumbuhan yang lebih cepat. 20 bayi prematur (berat badan 1280 dan 1176 Gram), yang di pijit 3 kali 15 menit selama 10 hari, mengalami kenaikan berat badan perhari 20% - 47% lebih banyak dari yang tidak dipijat. Penelitian pada bayi cukup bulan yang berusia 1-3 bulan, yang di pijat 15 menit, 2 kali seminggu selama 6 minggu juga didapatkan kenaikan berat badan 50% yang lebih dari kontrol. Jenis penelitian ini adalah survei eksplanotori yang bertujuan menjelaskan hubungan kausal antara variabel-variabel yang diteliti. Penelitian dilaksanakan di Wilayah kerja Puskesmas Simpang Limun. Di dalam penelitian ini, peneliti akan meneliti beberapa variabelEfektifitas Baby Solus Per Aqua (SPA) Terhadap Peningkatan Berat Badan Dengan Bayi Berat Badan Rendah Usia 4-9 BulanPemilihan variabel-variabel dalam penelitian ini didasarkan pada perilaku. Penelitian ini merupakan penelitiankuantitatif dengan, menggunakan desain quasi experiment pre post design with a comparison group karena dalam penelitian ini peneliti memberikan Intervensi atau intervensi pada subjek penelitian, kemudian Intervensi diukur dan dianalisis. Instrumen dibangun dengan mendalami teori dan konsep pada masing-masing variabel serta pengaruh dari satu variabel ke variabel lainnya. Hasil dari penelitian ini akan menciptakan suatu Perubahan perilaku masyarakat agar dapat mempraktekkan Baby Spa terhadap bayi ibu tersebut agar pertumbuhan dan perkembangan bayi dapat bertumbuh dengan baik
Formation epochs, star formation histories and sizes of massive early-type galaxies in cluster and field environments at z=1.2: insights from the rest-frame UV
We derive stellar masses, ages and star formation histories of massive
early-type galaxies in the z=1.237 RDCS1252.9-2927 cluster and compare them
with those measured in a similarly mass-selected sample of field contemporaries
drawn from the GOODS South Field. Robust estimates of these parameters are
obtained by comparing a large grid of composite stellar population models with
8-9 band photometry in the rest-frame NUV, optical and IR, thus sampling the
entire relevant domain of emission of the different stellar populations.
Additionally, we present new, deep -band photometry of both fields, giving
access to the critical FUV rest-frame, in order to constrain empirically the
dependence on the environment of the most recent star formation processes. We
find that early-type galaxies, both in the cluster and in the field, show
analogous optical morphologies, follow comparable mass vs. size relation, have
congruent average surface stellar mass densities and lie on the same Kormendy
relation. We also that a fraction of early-type galaxies in the field employ
longer timescales, , to assemble their mass than their cluster
contemporaries. Hence we conclude that, while the formation epoch of early-type
only depends on their mass, the environment does regulate the timescales of
their star formation histories. Our deep -band imaging strongly supports
this conclusions. It shows that cluster galaxies are at least 0.5 mag fainter
than their field contemporaries of similar mass and optical-to-infrared colors,
implying that the last episode of star formation must have happened more
recently in the field than in the cluster.Comment: 20pages, 10 figures. to appear on Ap
Persepsi Masyarakat terhadap Resiko Bencana Longsor di Dusun Blawong Kulon Desa Muncar Kecamatan Gemawang Kabupaten Temanggung
Dusun Blawong Kulon merupakan salah satu Dusun di Kabupaten Temanggung yang mempunyai resiko bencana longsor yang tinggi. Penelitian ini dilakukan untuk mengetahui persepsi resiko masyarakat terhadap bencana longsor. Penelitian ini bertujuan untuk a) Mengidentifikasi pengetahuan masyarakat terhadap ancaman bencana longsor b)Menganalisis persepsi resiko masyarakat terhadap ancaman bencana longsor c) Mengetahui upaya penanggulangan bencana yang dilakukan masyarakat dalam menghadapi ancaman bencana longsor. Metode kuantitatif digunakan untuk memperoleh data dengan menggunakan kuesioner dan skala likert serta menggunakan analisis statistik deskriptik dengan pemilihan sampel menggunakan probability sampling yaitu cluster sampling. Pengambilan sampel berada di delapan RT (Rumah Tangga) yang tersebar di Dusun Blawong Kulon dengan jumlah sampel 80 unit dengan unit Rumah Tangga. Hasil penelitian yang diperoleh adalah a) Penduduk Dusun Blawong Kulon mempunyai pengetahuan yang tinggi mengenai bencana longsor b) Penduduk Dusun Blawong Kulon mempunyai persepsi positif terhadap bencana longsor dengan agregat skala likert sebesar 60,8% c) dan sebanyak 51% penduduk Dusun Blawong Kulon mempunyai upaya penanggulangan bencana yang tinggi
Strain induced half-metal to semiconductor transition in GdN
We have investigated the electronic structure and magnetic properties of GdN
as a function of unit cell volume. Based on the first-principles calculations
of GdN, we observe that there is a transformation in conduction properties
associated with the volume increase: first from halfmetallic to semi-metallic,
then ultimately to semiconducting. We show that applying stress can alter the
carrier concentration as well as mobility of the holes and electrons in the
majority spin channel. In addition, we found that the exchange parameters
depend strongly on lattice constant, thus the Curie temperature of this system
can be enhanced by applying stress or doping impurities.Comment: 9 pages, 3 figure
Classification of multipartite entanglement containing infinitely many kinds of states
We give a further investigation of the range criterion and Low-to-High Rank
Generating Mode (LHRGM) introduced in \cite{Chen}, which can be used for the
classification of states under reversible local filtering
operations. By using of these techniques, we entirely classify the family of
states, which actually contains infinitely many kinds of
states. The classifications of true entanglement of
and systems are briefly listed respectively.Comment: 11 pages, revte
Coherent Population Trapping of Electron Spins in a Semiconductor
In high-purity n-type GaAs under strong magnetic field, we are able to
isolate a lambda system composed of two Zeeman states of neutral-donor bound
electrons and the lowest Zeeman state of bound excitons. When the two-photon
detuning of this system is zero, we observe a pronounced dip in the
excited-state photoluminescence indicating the creation of the coherent
population-trapped state. Our data are consistent with a steady-state
three-level density-matrix model. The observation of coherent population
trapping in GaAs indicates that this and similar semiconductor systems could be
used for various EIT-type experiments.Comment: 5 pages, 4 figures replaced 6/25/2007 with PRL versio
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