55,511 research outputs found
Recommended from our members
Caecilia volcani
Number of Pages: 2Integrative BiologyGeological Science
Triangle Singularities and XYZ Quarkonium Peaks
We discuss analytical properties of partial waves derived from projection of
a 4-legged amplitude with crossed-channel exchanges in the kinematic region of
the direct channel that corresponds to the XYZ peaks in charmonium and
bottomonium. We show that in general partial waves can develop anomalous branch
points in the vicinity of the direct channel physical region. In a specific
case, when these branch points lie on the opposite side of the unitary cut they
pinch the integration contour in a dispersion relation and if the pinch happens
close to threshold, the normal threshold cusp is enhanced. We show that this
effect only occurs if masses of resonances in the crossed channel are in a
specific, narrow range. We estimate the size of threshold enhancements
originating from these anomalous singularities in reactions where the Zc(3900)
and the Zb(10610) peaks have been observed.Comment: 10 pages, 9 figures, Version v3 to appear in Phys. Lett.
The molecular structure of the interface between water and a hydrophobic substrate is liquid-vapor like
With molecular simulation for water and a tunable hydrophobic substrate, we
apply the instantaneous interface construction [A. P. Willard and D. Chandler,
J. Phys. Chem. B, 114, 1954 (2010)] to examine the similarity between a
water-vapor interface and a water-hydrophobic surface interface. The intrinsic
interface refers to molecular structure in terms of distances from the
instantaneous interface. We show that attractive interactions between a
hydrophobic surface and water affect capillary wave fluctuations of the
instantaneous liquid interface, but these attractive interactions have
essentially no effect on the intrinsic interface. Further, the intrinsic
interface of liquid water and a hydrophobic substrate differs little from that
of water and its vapor.The same is not true, we show, for an interface between
water and a hydrophilic substrate. In that case, strong directional
substrate-water interactions disrupt the liquid-vapor-like interfacial hydrogen
bonding network.Comment: 6 pages, 5 figure
Effects of Latent Heating on Atmospheres of Brown Dwarfs and Directly Imaged Planets
Growing observations of brown dwarfs have provided evidence for strong
atmospheric circulation on these objects. Directly imaged planets share similar
observations, and can be viewed as low-gravity versions of brown dwarfs.
Vigorous condensate cycles of chemical species in their atmospheres are
inferred by observations and theoretical studies, and latent heating associated
with condensation is expected to be important in shaping atmospheric
circulation and influencing cloud patchiness. We present a qualitative
description of the mechanisms by which condensational latent heating influence
the circulation, and then illustrate them using an idealized general
circulation model that includes a condensation cycle of silicates with latent
heating and molecular weight effect due to rainout of condensate. Simulations
with conditions appropriate for typical T dwarfs exhibit the development of
localized storms and east-west jets. The storms are spatially inhomogeneous,
evolving on timescale of hours to days and extending vertically from the
condensation level to the tropopause. The fractional area of the brown dwarf
covered by active storms is small. Based on a simple analytic model, we
quantitatively explain the area fraction of moist plumes, and show its
dependence on radiative timescale and convective available potential energy. We
predict that, if latent heating dominates cloud formation processes, the
fractional coverage area by clouds decreases as the spectral type goes through
the L/T transition from high to lower effective temperature. This is a natural
consequence of the variation of radiative timescale and convective available
potential energy with spectral type.Comment: 13 pages, 8 figures, accepted for publication in Ap
Global-mean Vertical Tracer Mixing in Planetary Atmospheres II: Tidally Locked Planets
In Zhang Showman (2018, hereafter Paper I), we developed an analytical
theory of 1D eddy diffusivity for global-mean vertical tracer
transport in a 3D atmosphere. We also presented 2D numerical simulations on
fast-rotating planets to validate our theory. On a slowly rotating planet such
as Venus or a tidally locked planet (not necessarily a slow-rotator) such as a
hot Jupiter, the tracer distribution could exhibit significant longitudinal
inhomogeneity and tracer transport is intrinsically 3D. Here we study the
global-mean vertical tracer transport on tidally locked planets using 3D
tracer-transport simulations. We find that our analytical theory in
Paper I is validated on tidally locked planets over a wide parameter space.
strongly depends on the large-scale circulation strength, horizontal
mixing due to eddies and waves and local tracer sources and sinks due to
chemistry and microphysics. As our analytical theory predicted, on
tidally locked planets also exhibit three regimes In Regime I where the
chemical and microphysical processes are uniformly distributed across the
globe, different chemical species should be transported via different eddy
diffusivity. In Regime II where the chemical and microphysical processes are
non-uniform---for example, photochemistry or cloud formation that exhibits
strong day-night contrast---the global-mean vertical tracer mixing does not
always behave diffusively. In the third regime where the tracer is long-lived,
non-diffusive effects are significant. Using species-dependent eddy
diffusivity, we provide a new analytical theory of the dynamical quench points
for disequilibrium tracers on tidally locked planets from first principles.Comment: Accepted at ApJ, 16 pages, 12 figures. This is the part II. Part I is
"Global-mean Vertical Tracer Mixing in Planetary Atmospheres I: Theory and
Fast-rotating Planets
- …