3,871 research outputs found
Parochial Versus Universal Cooperation: Introducing a Novel Economic Game of Within- and Between-Group Interaction
Is the Sun Lighter than the Earth? Isotopic CO in the Photosphere, Viewed through the Lens of 3D Spectrum Synthesis
We consider the formation of solar infrared (2-6 micron) rovibrational bands
of carbon monoxide (CO) in CO5BOLD 3D convection models, with the aim to refine
abundances of the heavy isotopes of carbon (13C) and oxygen (18O,17O), to
compare with direct capture measurements of solar wind light ions by the
Genesis Discovery Mission. We find that previous, mainly 1D, analyses were
systematically biased toward lower isotopic ratios (e.g., R23= 12C/13C),
suggesting an isotopically "heavy" Sun contrary to accepted fractionation
processes thought to have operated in the primitive solar nebula. The new 3D
ratios for 13C and 18O are: R23= 91.4 +/- 1.3 (Rsun= 89.2); and R68= 511 +/- 10
(Rsun= 499), where the uncertainties are 1 sigma and "optimistic." We also
obtained R67= 2738 +/- 118 (Rsun= 2632), but we caution that the observed
12C17O features are extremely weak. The new solar ratios for the oxygen
isotopes fall between the terrestrial values and those reported by Genesis
(R68= 530, R6= 2798), although including both within 2 sigma error flags, and
go in the direction favoring recent theories for the oxygen isotope composition
of Ca-Al inclusions (CAI) in primitive meteorites. While not a major focus of
this work, we derive an oxygen abundance of 603 +/- 9 ppm (relative to
hydrogen; 8.78 on the logarithmic H= 12 scale). That the Sun likely is lighter
than the Earth, isotopically speaking, removes the necessity to invoke exotic
fractionation processes during the early construction of the inner solar
system
ΠΠΎΡΡΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠ°Ρ ΡΡΡΠ°ΡΠΈΡΠΈΠΊΠ°ΡΠΈΡ ΠΎΠ±Π»Π°ΠΊΠΎΠ² ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΈΠΌ ΠΏΠΎΠ»Π΅ΠΌ Π°ΡΠΌΠΎΡΡΠ΅ΡΡ Π² ΠΏΠ΅ΡΠΈΠΎΠ΄Ρ Π°ΠΊΡΠΈΠ²Π½ΠΎΠ³ΠΎ ΠΈ ΡΠΏΠΎΠΊΠΎΠΉΠ½ΠΎΠ³ΠΎ ΡΠΎΠ»Π½ΡΠ°
ΠΠΊΡΡΠ°Π»ΡΠ½ΠΎΡΡΡ. Π ΠΏΠΎΡΠ»Π΅Π΄Π½Π΅Π΅ Π΄Π΅ΡΡΡΠΈΠ»Π΅ΡΠΈΠ΅ Π½Π°Π±Π»ΡΠ΄Π°Π΅ΡΡΡ ΡΡΡΠ΅ΠΌΠΈΡΠ΅Π»ΡΠ½ΡΠΉ ΡΠΎΡΡ ΡΠ΅Π³ΠΈΠΎΠ½Π°Π»ΡΠ½ΠΎΠ³ΠΎ ΠΈ Π³Π»ΠΎΠ±Π°Π»ΡΠ½ΠΎΠ³ΠΎ ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΡ ΠΊΠ»ΠΈΠΌΠ°ΡΠ° Π² ΡΠ²ΡΠ·ΠΈ Ρ Ρ
ΠΎΠ·ΡΠΉΡΡΠ²Π΅Π½Π½ΠΎΠΉ Π΄Π΅ΡΡΠ΅Π»ΡΠ½ΠΎΡΡΡΡ ΡΠ΅Π»ΠΎΠ²Π΅ΠΊΠ°, ΠΊΠΎΡΠΎΡΠ°Ρ Π² ΡΠ²ΠΎΠΈΡ
ΠΌΠ°ΡΡΡΠ°Π±Π°Ρ
ΡΡΠ°Π»Π° ΡΠΎΠΈΠ·ΠΌΠ΅ΡΠΈΠΌΠ° Ρ ΠΏΡΠΈΡΠΎΠ΄Π½ΡΠΌΠΈ ΠΏΡΠΎΡΠ΅ΡΡΠ°ΠΌΠΈ. Π ΠΊΠ°ΡΠ΅ΡΡΠ²Π΅ ΠΈΠ½Π΄ΠΈΠΊΠ°ΡΠΎΡΠ° ΡΠ΅Ρ
Π½ΠΎΠ³Π΅Π½Π½ΠΎΠΉ Π½Π°Π³ΡΡΠ·ΠΊΠΈ ΠΌΠΎΠΆΠ΅Ρ Π²ΡΡΡΡΠΏΠ°ΡΡ ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ ΠΏΠΎΠ»Π΅ Π°ΡΠΌΠΎΡΡΠ΅ΡΡ, ΡΠ°ΠΊ ΠΊΠ°ΠΊ ΡΠ΅Ρ
Π½ΠΎΡΠΊΠΎΠ½ΠΎΠΌΠΈΡΠ΅ΡΠΊΠ°Ρ ΡΡΠ΅Π΄Π° Π³ΠΎΡΠΎΠ΄ΠΎΠ² ΠΏΡΠΈΠ²ΠΎΠ΄ΠΈΡ ΠΊ Π³Π»ΠΎΠ±Π°Π»ΡΠ½ΡΠΌ ΠΎΡΠΊΠ»ΠΎΠ½Π΅Π½ΠΈΡΠΌ ΠΈ ΠΌΠΎΠ΄ΠΈΡΠΈΠΊΠ°ΡΠΈΠΈ Π΅ΡΡΠ΅ΡΡΠ²Π΅Π½Π½ΡΡ
ΡΠΈΠ·ΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΏΠΎΠ»Π΅ΠΉ. ΠΠΎΡΡΠΎΠΌΡ Π½Π΅ΠΎΠ±Ρ
ΠΎΠ΄ΠΈΠΌΠΎΡΡΡ ΠΈΠ·ΡΡΠ΅Π½ΠΈΡ Π²Π»ΠΈΡΠ½ΠΈΡ ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΏΠΎΠ»Ρ Π°ΡΠΌΠΎΡΡΠ΅ΡΡ Π½Π° ΡΠ°ΡΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΠ΅ ΠΌΠ΅ΡΠ΅ΠΎΡΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠΎΠ² Π½Π΅ Π²ΡΠ·ΡΠ²Π°Π΅Ρ ΡΠΎΠΌΠ½Π΅Π½ΠΈΡ, ΡΠ°ΠΊ ΠΊΠ°ΠΊ ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ Π½Π° ΠΊΠ°ΡΠ΅ΡΡΠ²Π΅Π½Π½ΠΎΠΌ ΡΡΠΎΠ²Π½Π΅ ΠΏΡΠΎΡΠ²ΠΈΡΡ Β«ΡΠΎΠ½ΠΊΡΡΒ» ΡΡΡΡΠΊΡΡΡΡ ΡΡΡΠ°ΡΠΈΡΠΈΠΊΠ°ΡΠΈΠΈ Π°ΡΠΌΠΎΡΡΠ΅ΡΡ ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΈΠΌ ΠΏΠΎΠ»Π΅ΠΌ ΠΈ Π΅Π΅ ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ Π·Π° ΡΡΠ΅Ρ Π°Π½ΡΡΠΎΠΏΠΎΠ³Π΅Π½Π½ΠΎΠ³ΠΎ Π²ΠΎΠ·Π΄Π΅ΠΉΡΡΠ²ΠΈΡ. Π¦Π΅Π»Ρ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ: ΡΠ°ΡΡΠΌΠΎΡΡΠ΅ΡΡ ΠΌΠΎΡΡΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΡΡ ΡΡΡΠ°ΡΠΈΡΠΈΠΊΠ°ΡΠΈΡ ΠΎΠ±Π»Π°ΡΠ½ΡΡ
ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΠΉ ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΈΠΌ ΠΏΠΎΠ»Π΅ΠΌ Π°ΡΠΌΠΎΡΡΠ΅ΡΡ Π² ΠΏΠ΅ΡΠΈΠΎΠ΄ Π°ΠΊΡΠΈΠ²Π½ΠΎΠ³ΠΎ ΠΈ ΡΠΏΠΎΠΊΠΎΠΉΠ½ΠΎΠ³ΠΎ ΡΠΎΠ»Π½ΡΠ°. ΠΠ°Π½Π½ΡΠΉ ΠΏΠΎΠ΄Ρ
ΠΎΠ΄ ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ Π½Π° ΠΊΠ°ΡΠ΅ΡΡΠ²Π΅Π½Π½ΠΎΠΌ ΡΡΠΎΠ²Π½Π΅ ΠΏΡΠΎΡΡΠ½ΠΈΡΡ ΠΌΠ΅Ρ
Π°Π½ΠΈΠ·ΠΌ ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΡ ΠΏΡΠΎΡΠ΅ΡΡΠΎΠ² ΠΊΠΎΠ½Π΄Π΅Π½ΡΠ°ΡΠΈΠΈ Π²ΠΎΠ΄ΡΠ½ΠΎΠ³ΠΎ ΠΏΠ°ΡΠ° (Π½Π° ΠΏΡΠΈΠΌΠ΅ΡΠ΅ ΠΎΠ±Π»Π°ΠΊΠΎΠ²) ΡΠΌΠ΅Π½ΠΎΠΉ ΡΠΎΠ»Π½Π΅ΡΠ½ΠΎΠΉ Π°ΠΊΡΠΈΠ²Π½ΠΎΡΡΠΈ, ΠΊΠ°ΠΊ ΡΠΌΠ΅Π½ΡΡΠ΅Π½ΠΈΠ΅ ΠΊΠΎΠ»ΠΈΡΠ΅ΡΡΠ²Π° Π²ΠΎΠ·Π±ΡΠΆΠ΄Π΅Π½Π½ΡΡ
ΠΌΠΎΠ»Π΅ΠΊΡΠ» Π·Π° ΡΡΠ΅Ρ ΡΠ°Π·Π½ΠΎΠΉ ΠΈΠΎΠ½ΠΈΠ·Π°ΡΠΈΠΈ Π°ΡΠΌΠΎΡΡΠ΅ΡΡ, Π° ΡΠ°ΠΊΠΆΠ΅ ΠΏΠΎΡΡΡΠΎΠΈΡΡ ΡΠΈΠ·ΠΈΡΠ΅ΡΠΊΡΡ ΡΠ΅ΠΎΡΠΈΡ Π°Π½ΡΡΠΎΠΏΠΎΠ³Π΅Π½Π½ΠΎΠΉ Π½Π°Π³ΡΡΠ·ΠΊΠΈ ΠΎΡ ΠΏΡΠΎΠΌΡΡΠ»Π΅Π½Π½ΡΡ
ΠΏΡΠ΅Π΄ΠΏΡΠΈΡΡΠΈΠΉ Π½Π° Π°ΡΠΌΠΎΡΡΠ΅ΡΡ ΠΈ ΠΊΠ»ΠΈΠΌΠ°Ρ. ΠΠ±ΡΠ΅ΠΊΡ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ: ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ ΠΏΠΎΠ»Π΅ Π°ΡΠΌΠΎΡΡΠ΅ΡΡ, ΠΎΠ±Π»Π°ΠΊΠ°. ΠΠ΅ΡΠΎΠ΄ΠΈΠΊΠ° ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΠΏΠΎΡΡΡΠΎΠ΅Π½Π° Π½Π° Π΄Π΅ΡΠ°Π»ΡΠ½ΠΎΠΌ ΡΡΠ°ΡΠΈΡΡΠΈΡΠ΅ΡΠΊΠΎΠΌ Π°Π½Π°Π»ΠΈΠ·Π΅ ΠΏΠΎ Π΄Π°Π½Π½ΡΠΌ ΡΠ°ΠΌΠΎΠ»Π΅ΡΠ½ΠΎΠ³ΠΎ Π·ΠΎΠ½Π΄ΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π² ΠΏΠ΅ΡΠΈΠΎΠ΄ ΠΌΠ΅ΠΆΠ΄ΡΠ½Π°ΡΠΎΠ΄Π½ΠΎΠ³ΠΎ Π³Π΅ΠΎΡΠΈΠ·ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ Π³ΠΎΠ΄Π° ΠΈ ΠΌΠ΅ΠΆΠ΄ΡΠ½Π°ΡΠΎΠ΄Π½ΠΎΠ³ΠΎ Π³Π΅ΠΎΡΠΈΠ·ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠΎΡΡΡΠ΄Π½ΠΈΡΠ΅ΡΡΠ²Π° 1958-1964 Π³Π³. Π Π΅Π·ΡΠ»ΡΡΠ°ΡΡ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ. ΠΠΎΠ»ΡΡΠ΅Π½Ρ ΠΎΡΠ΅Π½ΠΊΠΈ ΡΠ°Π΄ΠΈΠ°ΡΠΈΠΎΠ½Π½ΡΡ
ΡΠ΅ΡΠ΅Π½ΠΈΠΉ Π΄Π»Ρ ΠΌΠΎΠ»Π΅ΠΊΡΠ» ΡΡΠ°Π½Π΄Π°ΡΡΠ½ΠΎΠΉ Π°ΡΠΌΠΎΡΡΠ΅ΡΡ ΠΈ ΠΊΠΎΠ½Π΄Π΅Π½ΡΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠΉ ΡΠ°Π·Ρ (ΠΎΠ±Π»Π°ΡΠ½ΡΠ΅ Π°ΡΡΠΎΠ·ΠΎΠ»ΠΈ) Π² Π³Π΅ΠΎΠΌΠ΅ΡΡΠΈΡΠ΅ΡΠΊΠΎΠΌ ΠΏΡΠΈΠ±Π»ΠΈΠΆΠ΅Π½ΠΈΠΈ, ΠΊΠΎΡΠΎΡΡΠ΅ ΠΏΠΎΠΊΠ°Π·ΡΠ²Π°ΡΡ, ΡΡΠΎ ΠΏΡΠΈ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠ½ΠΎΠΌ ΡΠ°Π΄ΠΈΡΡΠ΅ ΠΊΠ°ΠΏΠ΅Π»Ρ r-10[-3]ΡΠΌ ΠΈΠΎΠ½ΠΈΠ·Π°ΡΠΈΡ ΠΎΡ ΠΊΠΎΠ½Π΄Π΅Π½ΡΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠΉ ΡΠ°Π·Ρ ΡΠΎΠΈΠ·ΠΌΠ΅ΡΠΈΠΌΠ° Ρ ΡΠΎΠ½ΠΎΠ½ΠΎΠ²ΠΎΠΉ ΠΈΠΎΠ½ΠΈΠ·Π°ΡΠΈΠ΅ΠΉ Π°ΡΠΌΠΎΡΡΠ΅ΡΡ. ΠΡΠΈΠ²Π΅Π΄Π΅Π½Π° ΠΊΠΎΡΡΠ΅Π»ΡΡΠΈΠΎΠ½Π½Π°Ρ Π·Π°Π²ΠΈΡΠΈΠΌΠΎΡΡΡ ΡΡΠ΅Π΄Π½Π΅ΠΉ Π²ΠΎΠ΄Π½ΠΎΡΡΠΈ ΠΎΠ±Π»Π°ΠΊΠ° ΠΈ Π²Π΅ΡΡΠΈΠΊΠ°Π»ΡΠ½ΠΎΠ³ΠΎ ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΏΠΎΠ»Ρ. ΠΠ½Π°Π»ΠΈΠ· ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠΎΠ² ΠΏΠΎΠΊΠ°Π·Π°Π», ΡΡΠΎ ΡΡΠ΅Π΄Π½Π΅Π³ΠΎΠ΄ΠΎΠ²ΠΎΠ΅ ΡΠ°ΡΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΠ΅ Π²ΠΎΠ΄Π½ΠΎΡΡΠΈ ΠΈΠΌΠ΅Π΅Ρ Π²ΡΡΠΎΠΊΡΡ ΠΊΠΎΡΡΠ΅Π»ΡΡΠΈΡ ΡΠΎ ΡΡΠ΅Π΄Π½Π΅Π³ΠΎΠ΄ΠΎΠ²ΡΠΌ Π²Π΅ΡΡΠΈΠΊΠ°Π»ΡΠ½ΡΠΌ ΡΠ°ΡΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΠ΅ΠΌ Π½Π°ΠΏΡΡΠΆΠ΅Π½Π½ΠΎΡΡΠΈ ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΏΠΎΠ»Ρ Π΄Π»Ρ Π΄Π°Π½Π½ΠΎΠ³ΠΎ ΡΠ΅Π³ΠΈΠΎΠ½Π°. ΠΠ΅ΡΠΎΠ΄Π°ΠΌΠΈ Π΄Π΅ΡΠ°Π»ΡΠ½ΠΎΠ³ΠΎ ΡΡΠ°ΡΠΈΡΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ Π°Π½Π°Π»ΠΈΠ·Π° Π½Π°ΠΉΠ΄Π΅Π½Π° Π²Π·Π°ΠΈΠΌΠΎΡΠ²ΡΠ·Ρ Π²ΡΡΠΎΡΡ ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΡ ΠΎΠ±Π»Π°ΠΊΠΎΠ² Ρ ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΈΠΌ ΠΏΠΎΠ»Π΅ΠΌ Π°ΡΠΌΠΎΡΡΠ΅ΡΡ. ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ, ΡΡΠΎ ΡΠ°ΡΡΠΎΡΠ° ΠΏΠΎΠ²ΡΠΎΡΡΠ΅ΠΌΠΎΡΡΠΈ Π½ΠΈΠΆΠ½Π΅ΠΉ Π³ΡΠ°Π½ΠΈΡΡ ΠΎΠ±Π»Π°ΠΊΠΎΠ² ΡΠΎΠ²ΠΏΠ°Π΄Π°Π΅Ρ Ρ Π»ΠΎΠΊΠ°Π»ΡΠ½ΡΠΌΠΈ ΡΠΎΡΠΊΠ°ΠΌΠΈ ΡΠ°Π²Π½ΠΎΠ²Π΅ΡΠΈΡ ΠΏΠ»ΠΎΡΠ½ΠΎΡΡΠΈ ΠΎΠ±ΡΠ΅ΠΌΠ½ΠΎΠ³ΠΎ Π·Π°ΡΡΠ΄Π° Π΄Π»Ρ ΡΡΠΎΠΉ ΠΆΠ΅ ΡΠΈΡΠΎΡΡ.Relevance of the research. In recent decade, regional and global climate has changed significantly due to human activities, which became comparable with natural processes. The electric field of atmosphere can serve as an indicator of anthropogenic impact, as the technical and economic environment of cities results in global deviations and modification of natural physical fields. Therefore, there is no doubt in the necessity to study the influence of the atmospheric electric field on distribution of meteorological parameters, since it allows us to reveal qualitatively the Β«thinΒ» atmospheric stratification structure of the electric field and its change owing to anthropogenic impact. The aim of the research is to consider the morphological stratification of cloud formations by the atmospheric electric field in the period of the active and quiet sun. This approach allows us to clarify qualitatively the mechanism of change in water vapor condensation (on the example of clouds) by the solar activity change as the decrease in the number of excited molecules owing to different ionization of the atmosphere, as well as to build a physical theory of anthropogenic load from industrial plants on the atmosphere and climate. Research subject: the electric field of the atmosphere, clouds. Research technique: detailed statistical analysis of the data on an aircraft sounding during the International Geophysical Year and the International Geophysical Cooperation in 1958-1964. Results. The author has obtained the estimations of radiation cross-sections for the molecules of the standard atmosphere and the condensed phase (cloud aerosols) in geometric approximation. They show that when the characteristic radius is equal to r-10[-3] cm the ionization of the condensed phase is commensurate with the background ionization. The paper introduces the correlative relationship between average water content of clouds and vertical electric field. The analysis of the results demonstrates that the average annual distribution of water content is strongly correlated with the average vertical distribution of the electric field in this region. Using the methods of the detailed statistical analysis the author revealed the relationship between the height of cloud formation and the electric field of the atmosphere. It is shown that the repetition frequency of a cloud lower boundary demonstrates the high coincidence with local sites of neutrality of a bulk charge density for the same latitude
Heavy boson production through the collision of an ultrahigh-energy neutrino on a target nucleon
We discuss W and Z production through the deep inelastic neutrino-nucleon
scattering in the context of the standard model SU(3)x SU(2)x U(1) of the
strong and electroweak interactions. We find the cross section rates for the
process neutrino + nucleon --> lepton(-) + W(+) + X for the case of
ultrahigh-energy neutrinos colliding on a target nucleon.Comment: 20 pages, 6 figure
Vortices, shocks, and heating in the solar photosphere: effect of a magnetic field
Aims: We study the differences between non-magnetic and magnetic regions in
the flow and thermal structure of the upper solar photosphere. Methods:
Radiative MHD simulations representing a quiet region and a plage region,
respectively, which extend into the layers around the temperature minimum, are
analyzed. Results: The flow structure in the upper photospheric layers of the
two simulations is considerably different: the non-magnetic simulation is
dominated by a pattern of moving shock fronts while the magnetic simulation
shows vertically extended vortices associated with magnetic flux
concentrations. Both kinds of structures induce substantial local heating. The
resulting average temperature profiles are characterized by a steep rise above
the temperature minimum due to shock heating in the non-magnetic case and by a
flat photospheric temperature gradient mainly caused by Ohmic dissipation in
the magnetic run. Conclusions: Shocks in the quiet Sun and vortices in the
strongly magnetized regions represent the dominant flow structures in the
layers around the temperature minimum. They are closely connected with
dissipation processes providing localized heating.Comment: Accepted for publicaton in A&
Long-term magnetic field stability of Vega
We present new spectropolarimetric observations of the normal A-type star
Vega, obtained during the summer of 2010 with NARVAL at T\'elescope Bernard
Lyot (Pic du Midi Observatory). This new time-series is constituted of 615
spectra collected over 6 different nights. We use the
Least-Square-Deconvolution technique to compute, from each spectrum, a mean
line profile with a signal-to-noise ratio close to 20,000. After averaging all
615 polarized observations, we detect a circularly polarized Zeeman signature
consistent in shape and amplitude with the signatures previously reported from
our observations of 2008 and 2009. The surface magnetic geometry of the star,
reconstructed using the technique of Zeeman-Doppler Imaging, agrees with the
maps obtained in 2008 and 2009, showing that most recognizable features of the
photospheric field of Vega are only weakly distorted by large-scale surface
flows (differential rotation or meridional circulation).Comment: Proceedings of the conference "Stellar polarimetry: from birth to
death", 2011 Jun 27-30, Madiso
Morphology and Dynamics of the Low Solar Chromosphere
The Interferometric Bidimensional Spectrometer (IBIS) installed at the Dunn
Solar Telescope of the NSO/SP is used to investigate the morphology and
dynamics of the lower chromosphere and the virtually non-magnetic fluctosphere
below. The study addresses in particular the structure of magnetic elements
that extend into these layers. We choose different quiet Sun regions in and
outside coronal holes. In inter-network regions with no significant magnetic
flux contributions above the detection limit of IBIS, we find intensity
structures with the characteristics of a shock wave pattern. The magnetic flux
elements in the network are long lived and seem to resemble the spatially
extended counterparts to the underlying photospheric magnetic elements. We
suggest a modification to common methods to derive the line-of-sight magnetic
field strength and explain some of the difficulties in deriving the magnetic
field vector from observations of the fluctosphere.Comment: accepted by ApJ, 16 pages, 8 figure
Manifolds with 1/4-pinched flag curvature
We say that a nonnegatively curved manifold has quarter pinched flag
curvature if for any two planes which intersect in a line the ratio of their
sectional curvature is bounded above by 4. We show that these manifolds have
nonnegative complex sectional curvature. By combining with a theorem of Brendle
and Schoen it follows that any positively curved manifold with strictly quarter
pinched flag curvature must be a space form. This in turn generalizes a result
of Andrews and Nguyen in dimension 4. For odd dimensional manifolds we obtain
results for the case that the flag curvature is pinched with some constant
below one quarter, one of which generalizes a recent work of Petersen and Tao
Charged Randall-Sundrum black holes and N=4 super Yang-Mills in AdS(2)xS(2)
We obtain some exact results for black holes in the Randall-Sundrum model
with a single brane. We consider an extreme black hole charged with respect to
a Maxwell field on the brane. The near-horizon geometry is determined. The
induced metric on the brane and the black hole entropy are compared with the
predictions of 4d General Relativity. There is good agreement for large black
holes, with calculable subleading corrections. As a separate application, the
bulk solution provides a gravitational dual for (strongly coupled, large N) N=4
SYM in AdS(2)xS(2) for arbitrary relative size of AdS(2) and S(2).Comment: 13 page
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