2,848 research outputs found
On the Role of Charmed Meson Loops in Charmonium Decays
We investigate the effect of intermediate charmed meson loops on the M1
radiative decays and
as well as the isospin violating
hadronic decays using heavy hadron
chiral perturbation theory (HHPT). The calculations include tree level as
well as one loop diagrams and are compared to the latest data from CLEO and
BES-III. Our fit constrains the couplings of 1S and 2S charmonium multiplets to
charmed mesons, denoted and , respectively. We find that
there are two sets of solutions for and . One set, which
agrees with previous values of the product extracted from
analyses that consider only loop contributions to , can only fit data on radiative decays with fine-tuned
cancellations between tree level diagrams and loops in that process. The other
solution for and leads to couplings that are smaller by a
factor of 2.3. In this case tree level and loop contributions are of comparable
size and the numerical values of the tree level contributions to radiative
decays are consistent with estimates based on the quark model as well as
non-relativistic QCD (NRQCD). This result shows that tree level HHPT
couplings are as important as the one loop graphs with charmed mesons in these
charmonium decays. The couplings and are also important for
the calculations of the decays of charmed meson bound states, such as the
X(3872), to conventional charmonia.Comment: 16 pages, 3 figures, minor modifications, more references adde
Signature of Quantum Criticality in the Density Profiles of Cold Atom Systems
In recent years, there is considerable experimental effort using cold atoms
to study strongly correlated many-body systems. One class of phenomena of
particularly interests is quantum critical (QC) phenomena. While prevalent in
many materials, these phenomena are notoriously difficult theoretical problems
due to the vanishing of energy scales in QC region. So far, there are no
systematic ways to deduce QC behavior of bulk systems from the data of trapped
atomic gases. Here, we present a simple algorithm to use the experimental
density profile to determine the T=0 phase boundary of bulk systems, as well as
the scaling functions in QC regime. We also present another scheme for removing
finite size effects of the trap. We demonstrate the validity of our schemes
using exactly soluble models.Comment: 4 pages, 5 figure
Further Results on Coding for Reliable Communication over Packet Networks
In "On Coding for Reliable Communication over Packet Networks" (Lun, Medard,
and Effros, Proc. 42nd Annu. Allerton Conf. Communication, Control, and
Computing, 2004), a capacity-achieving coding scheme for unicast or multicast
over lossy wireline or wireless packet networks is presented. We extend that
paper's results in two ways: First, we extend the network model to allow
packets received on a link to arrive according to any process with an average
rate, as opposed to the assumption of Poisson traffic with i.i.d. losses that
was previously made. Second, in the case of Poisson traffic with i.i.d. losses,
we derive error exponents that quantify the rate at which the probability of
error decays with coding delay.Comment: 5 pages; to appear in Proc. 2005 IEEE International Symposium on
Information Theory (ISIT 2005
SCOZA for Monolayer Films
We show the way in which the self-consistent Ornstein-Zernike approach
(SCOZA) to obtaining structure factors and thermodynamics for Hamiltonian
models can best be applied to two-dimensional systems such as thin films. We
use the nearest-neighbor lattice gas on a square lattice as an illustrative
example.Comment: 10 pages, 5 figure
Energy non-equipartition in systems of inelastic, rough spheres
We calculate and verify with simulations the ratio between the average
translational and rotational energies of systems with rough, inelastic
particles, either forced or freely cooling. The ratio shows non-equipartition
of energy. In stationary flows, this ratio depends mainly on the particle
roughness, but in nonstationary flows, such as freely cooling granular media,
it also depends strongly on the normal dissipation. The approach presented here
unifies and simplifies different results obtained by more elaborate kinetic
theories. We observe that the boundary induced energy flux plays an important
role.Comment: 4 pages latex, 4 embedded eps figures, accepted by Phys Rev
Monitoring Snow Cover and Snowmelt Dynamics and Assessing their Influences on Inland Water Resources
Snow is one of the most vital cryospheric components owing to its wide coverage as well as its unique physical characteristics. It not only affects the balance of numerous natural systems but also influences various socio-economic activities of human beings. Notably, the importance of snowmelt water to global water resources is outstanding, as millions of populations rely on snowmelt water for daily consumption and agricultural use. Nevertheless, due to the unprecedented temperature rise resulting from the deterioration of climate change, global snow cover extent (SCE) has been shrinking significantly, which endangers the sustainability and availability of inland water resources. Therefore, in order to understand cryo-hydrosphere interactions under a warming climate, (1) monitoring SCE dynamics and snowmelt conditions, (2) tracking the dynamics of snowmelt-influenced waterbodies, and (3) assessing the causal effect of snowmelt conditions on inland water resources are indispensable. However, for each point, there exist many research questions that need to be answered. Consequently, in this thesis, five objectives are proposed accordingly. Objective 1: Reviewing the characteristics of SAR and its interactions with snow, and exploring the trends, difficulties, and opportunities of existing SAR-based SCE mapping studies; Objective 2: Proposing a novel total and wet SCE mapping strategy based on freely accessible SAR imagery with all land cover classes applicability and global transferability; Objective 3: Enhancing total SCE mapping accuracy by fusing SAR- and multi-spectral sensor-based information, and providing total SCE mapping reliability map information; Objective 4: Proposing a cloud-free and illumination-independent inland waterbody dynamics tracking strategy using freely accessible datasets and services; Objective 5: Assessing the influence of snowmelt conditions on inland water resources
Monitoring Summertime Erosion Patterns Over an Arctic Permafrost Coast with Recent Sub-meter Resolution Microsatellite SAR Data
Arctic coasts experience some of the highest rates of erosion in the world, particularly due to permafrost degradation resulting from the recent exacerbation of climate change. Therefore, not only have coastal defense and energy facilities been threatened, but maintenance costs for the infrastructure of cold regions have also risen. To monitor the coastal erosion pattern of the circum-Arctic, earlier studies often employ spaceborne or airborne optical multi-spectral images to depict shoreline changes, which are limited by frequent clouds and haze in Arctic regions and, thus, hamper the time-series analysis. Instead, this study aims to explore the synthetic aperture radar (SAR) images, especially the recently developed microsatellite SAR data, which provide unprecedented high-resolution at a sub-meter scale, to measure the summertime spatio-temporal dynamics of an ice-rich permafrost coast along the Beaufort Sea, Alaska. The results reveal a maximum shoreline change envelope (SCE) of 64.89 m during the three-month study period. To examine the differences between the estimations and the observations derived from the conventional Sentinel-1 data, the proposed multi-stage statistical-driven scheme is used. A statistically significant positive relationship between two depicted SCEs with the presence of heteroscedasticity is confirmed. In detail, the agreement between two SCEs increases with the magnitude of the SCE, indicating that the microsatellite SAR can depict more trivial changes in coastline positions. Founded on the results and detailed discussion on the uniqueness and limitations of current SAR sensors, the promising opportunity to utilize the blooming microsatellite SAR datasets for coastal monitoring is highlighted
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