890 research outputs found
Resonant Enhancement of Inelastic Light Scattering in Strongly Correlated Materials
We use dynamical mean field theory to find an exact solution for inelastic
light scattering in strongly correlated materials such as those near a
quantum-critical metal-insulator transition. We evaluate the results for
(Raman) scattering and find that resonant effects can be quite
large, and yield a triple resonance, a significant enhancement of nonresonant
scattering peaks, a joint resonance of both peaks when the incident photon
frequency is on the order of , and the appearance of an isosbestic point in
all symmetry channels for an intermediate range of incident photon frequencies.Comment: 5 pages RevTex, 4 Figures ep
First supernovae in dwarf protogalaxies
(Abridged) We explore numerically the chemical, thermal, and dynamical
evolution of a shell formed by a high-energy supernova explosion (
erg) in dwarf protogalaxies with total mass at a redshift
. We consider two initial configurations for the baryonic matter, one
without rotation and the other having the ratio of rotational to gravitational
energy . The (non-rotating) dark matter halo is described by a
quasi-isothermal sphere. We find that the dynamics of the shell is different in
protogalaxies with and without rotation. For instance, the Rayleigh-Taylor
instability in the shell develops faster in protogalaxies without rotation. The
fraction of a blown-away baryonic mass is approximately twice as large in
models with rotation () than in models without rotation. On the other
hand, the chemical evolution of gas in protogalaxies with and without rotation
is found to be similar. The relative number densities of molecular hydrogen and
HD molecules in the cold gas ( K) saturate at typical values of
and , respectively. The clumps formed in the fragmented
shell move with velocities that are at least twice as large as the escape
velocity. The mass of the clumps is \sim 0.1-10 \msun, which is lower than
the Jeans mass. We conclude that the clumps are pressure supported. A supernova
explosion with energy ergs destructs our model protogalaxy. The
clumps formed in the fragmented shell are pressure supported. We conclude that
protogalaxies with total mass are unlikely to form stars
due to high-energy supernova explosions of the first stars.Comment: 12 pages, 8 figures, accepted in A&
Infrared and sub-mm observations of outbursting young stars with Herschel and Spitzer
Episodic accretion plays an important role in the evolution of young stars.
Although it has been under investigation for a long time, the origin of such
episodic accretion events is not yet understood. We investigate the dust and
gas emission of a sample of young outbursting sources in the infrared to get a
better understanding of their properties and circumstellar material, and we use
the results in a further work to model the objects. We used Herschel data, from
our PI program of 12 objects and complemented with archival observations to
obtain the spectral energy distributions (SEDs) and spectra of our targets. We
report here the main characteristics of our sample, focussing on the SED
properties and on the gas emission lines detected in the PACS and SPIRE
spectra. The SEDs of our sample show the diversity of the outbursting sources,
with several targets showing strong emission in the far-infrared from the
embedded objects. Most of our targets reside in a complex environment, which we
discuss in detail. We detected several atomic and molecular lines, in
particular rotational CO emission from several transitions from J=38-37 to
J=4-3. We constructed rotational diagrams for the CO lines, and derived in
three domains of assumed local thermodynamic equilibrium (LTE) temperatures and
column densities, ranging mainly between 0-100 K and 400-500K. We confirm
correlation in our sample between intense CO emission and the column
density of the warm domain of CO, N(warm). We notice a strong increase in
luminosity of HH 381 IRS and a weaker increase for PP 13 S, which shows the
beginning of an outburst.Comment: 23 pages, 17 figures, A&A accepte
Prescriptions for the scaling variable of the nucleon structure function in nuclei
We tested several choices of the in-medium value of the Bjorken scaling
variable assuming the nucleon structure function in nucleus to be the same as
that of free nucleon. The results unambiguously show that it is different.Comment: 11 pages, 3 figures, 1 tabl
Assessment of attitudes to COVID-19 vaccinophylaxis of professional risk groups
An assessment was made of the attitude towards vaccine prevention as a method of preventing infectious diseases and vaccine prevention of COVID-19 among the main occupational risk groups (medical workers with secondary and higher education, education workers).ΠΡΠΎΠ²Π΅Π΄Π΅Π½Π° ΠΎΡΠ΅Π½ΠΊΠ° ΠΎΡΠ½ΠΎΡΠ΅Π½ΠΈΡ ΠΊ Π²Π°ΠΊΡΠΈΠ½ΠΎΠΏΡΠΎΡΠΈΠ»Π°ΠΊΡΠΈΠΊΠ΅ ΠΊΠ°ΠΊ ΠΊ ΠΌΠ΅ΡΠΎΠ΄Ρ ΠΏΡΠΎΡΠΈΠ»Π°ΠΊΡΠΈΠΊΠΈ ΠΈΠ½ΡΠ΅ΠΊΡΠΈΠΎΠ½Π½ΡΡ
Π·Π°Π±ΠΎΠ»Π΅Π²Π°Π½ΠΈΠΉ ΠΈ ΠΊ Π²Π°ΠΊΡΠΈΠ½ΠΎΠΏΡΠΎΡΠΈΠ»Π°ΠΊΡΠΈΠΊΠ΅ COVID-19 ΡΡΠ΅Π΄ΠΈ ΠΎΡΠ½ΠΎΠ²Π½ΡΡ
Π³ΡΡΠΏΠΏ ΠΏΡΠΎΡΠ΅ΡΡΠΈΠΎΠ½Π°Π»ΡΠ½ΠΎΠ³ΠΎ ΡΠΈΡΠΊΠ° (ΠΌΠ΅Π΄ΠΈΡΠΈΠ½ΡΠΊΠΈΠ΅ ΡΠ°Π±ΠΎΡΠ½ΠΈΠΊΠΈ ΡΠΎ ΡΡΠ΅Π΄Π½ΠΈΠΌ ΠΈ Π²ΡΡΡΠΈΠΌ ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ, ΡΠ°Π±ΠΎΡΠ½ΠΈΠΊΠΈ ΡΡΠ΅ΡΡ ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΡ)
A high-pressure hydrogen time projection chamber for the MuCap experiment
The MuCap experiment at the Paul Scherrer Institute performed a
high-precision measurement of the rate of the basic electroweak process of
nuclear muon capture by the proton, . The
experimental approach was based on the use of a time projection chamber (TPC)
that operated in pure hydrogen gas at a pressure of 10 bar and functioned as an
active muon stopping target. The TPC detected the tracks of individual muon
arrivals in three dimensions, while the trajectories of outgoing decay (Michel)
electrons were measured by two surrounding wire chambers and a plastic
scintillation hodoscope. The muon and electron detectors together enabled a
precise measurement of the atom's lifetime, from which the nuclear muon
capture rate was deduced. The TPC was also used to monitor the purity of the
hydrogen gas by detecting the nuclear recoils that follow muon capture by
elemental impurities. This paper describes the TPC design and performance in
detail.Comment: 15 pages, 13 figures, to be submitted to Eur. Phys. J. A; clarified
section 3.1.2 and made minor stylistic corrections for Eur. Phys. J. A
requirement
The outburst of an embedded low-mass YSO in L1641
Strong outbursts in very young and embedded protostars are rare and not yet
fully understood. They are believed to originate from an increase of the mass
accretion rate onto the source. We report the discovery of a strong outburst in
a low-mass embedded young stellar object (YSO), namely 2MASS-J05424848-0816347
or [CTF93]216-2, as well as its photometric and spectroscopic follow-up. Using
near- to mid-IR photometry and NIR low-resolution spectroscopy, we monitor the
outburst, deriving its magnitude, duration, as well as the enhanced accretion
luminosity and mass accretion rate. [CTF93]216-2 increased in brightness by
~4.6, 4.0, 3.8, and 1.9 mag in the J, H, Ks bands and at 24 um, respectively,
corresponding to an L_bol increase of ~20 L_sun. Its early spectrum, probably
taken soon after the outburst, displays a steep almost featureless continuum,
with strong CO band heads and H_2O broad-band absorption features, and Br gamma
line in emission. A later spectrum reveals more absorption features, allowing
us to estimate T_eff~3200 K, M~0.25 M_sun, and mass accretion rate~1.2x10^{-6}
M_sun yr^{-1}. This makes it one of the lowest mass YSOs with a strong outburst
so far discovered.Comment: To be published in A&A letter; 5 pages, 4 figure
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