273,372 research outputs found
An Alternative to Spinning Dust for the Microwave Emission of LPH 201.663+1.643: an Ultracompact HII Region
The microwave spectral energy distribution of the dusty, diffuse H II region
LPH 201.663+1.643 has been interpreted by others as tentative evidence for
microwave emission from spinning dust grains. We present an alternative
interpretation for that particular object; specifically, that an ultracompact H
II region embedded within the dust cloud would explain the available
observations as well or better than spinning dust. Parameters for the size,
surface brightness, and flux density of the putative ultracompact HII region,
derived from the microwave observations, are within known ranges. A possible
candidate for such an ultracompact H II region is IRAS 06337+1051, based upon
its infrared colors. However, IRAS 06337+1051's infrared flux appears to be too
small to be consistent with the microwave flux required for this alternative
model to explain the observations.Comment: 11 pages, 3 figures, accepted to ApJ Letter
Pinned Bilayer Wigner Crystals with Pseudospin Magnetism
We study a model of \textit{pinned} bilayer Wigner crystals (WC) and focus on
the effects of interlayer coherence (IC) on pinning. We consider both a
pseudospin ferromagnetic WC (FMWC) with IC and a pseudospin antiferromagnetic
WC (AFMWC) without IC. Our central finding is that a FMWC can be pinned more
strongly due to the presence of IC. One specific mechanism is through the
disorder induced interlayer tunneling, which effectively manifests as an extra
pinning in a FMWC. We also construct a general "effective disorder" model and
effective pinning Hamiltonian for the case of FMWC and AFMWC respectively.
Under this framework, pinning in the presence of IC involves
\textit{interlayer} spatial correlation of disorder in addition to intralayer
correlation, leading to \textit{enhanced} pinning in the FMWC. The pinning mode
frequency (\wpk) of a FMWC is found to decease with the effective layer
separation, whereas for an AFMWC the opposite behavior is expected. An abrupt
drop of \wpk is predicted at a transition from a FMWC to AFMWC. Possible
effects of in-plane magnetic fields and finite temperatures are addressed.
Finally we discuss some other possible ramifications of the FMWC as an
electronic supersolid-like phase.Comment: Slightly revised. The final version is published on PR
Longevity impact on life insurers in low interest rate environment
This paper aims at shedding some light on the interplay between two key risk factors affecting most life insurance products, namely biometric and investment risk. We enhance the pioneering model by Briys and de Varenne, featuring a stylized participating life insurance company by explicitly tying benefits to the survivorship of a cohort of policyholders. In particular, we allow for the two main components of biometric risk, that is systematic (longevity) risk and diversifiable (process) risk
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Lateral shearing interferometry for high-NA EUV wavefront metrology
We present a lateral shearing interferometer suitable for high-NA EUV wavefront metrology. In this interferometer, a geometric model is used to accurately characterize and predict systematic errors that come from performing interferometry at high NA. This interferometer is compatible with various optical geometries, including systems where the image plane is tilted with respect to the optical axis, as in the Berkeley MET5. Simulation results show that the systematic errors in tilted geometries can be reduced by aligning the shearing interferometer grating and detector parallel to the image plane. Subsequent residual errors can be removed by linear fitting
Image Properties of Embedded Lenses
We give analytic expressions for image properties of objects seen around
point mass lenses embedded in a flat CDM universe. An embedded lens in
an otherwise homogeneous universe offers a more realistic representation of the
lens's gravity field and its associated deflection properties than does the
conventional linear superposition theory. Embedding reduces the range of the
gravitational force acting on passing light beams thus altering all quantities
such as deflection angles, amplifications, shears and Einstein ring sizes.
Embedding also exhibits the explicit effect of the cosmological constant on
these same lensing quantities. In this paper we present these new results and
demonstrate how they can be used. The effects of embedding on image properties,
although small i.e., usually less than a fraction of a percent, have a more
pronounced effect on image distortions in weak lensing where the effects can be
larger than 10%. Embedding also introduces a negative surface mass density for
both weak and strong lensing, a quantity altogether absent in conventional
Schwarzschild lensing. In strong lensing we find only one additional quantity,
the potential part of the time delay, which differs from conventional lensing
by as much as 4%, in agreement with our previous numerical estimates.Comment: 17 pages, 6 figure
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