791 research outputs found
Stokes-space formalism for Bragg scattering in a fiber
Optical frequency conversion by four-wave mixing (Bragg scattering) in a
fiber is considered. The evolution of this process can be modeled using the
signal and idler amplitudes, which are complex, or Stokes-like parameters,
which are real. The Stokes-space formalism allows one to visualize power and
phase information simultaneously, and produces a simple evolution equation for
the Stokes parameters
Gamma positioning and market quality
In this paper, we study the effect of the gamma positioning of dynamic hedgers on market quality through simulations. In our zero-intelligence model, the presence of dynamic hedgers enhances market liquidity under normal conditions. However, positive gamma helps sustain liquidity in stressed scenarios, while negative gamma depletes it. We find that an increase in the net gamma positioning of dynamic hedgers reduces volatility and increases market stability, whereas a negative gamma positioning increases volatility and makes the market more prone to failure. Price discovery typically worsens when dynamic hedgers become more prevalent, regardless of the sign of their positioning. Our findings imply that steering the net gamma position of dynamic hedgers can be considered a policy instrument to improve market quality, especially for instruments with low liquidity or low traded volume.</p
Gamma positioning and market quality
In this paper, we study the effect of the gamma positioning of dynamic hedgers on market quality through simulations. In our zero-intelligence model, the presence of dynamic hedgers enhances market liquidity under normal conditions. However, positive gamma helps sustain liquidity in stressed scenarios, while negative gamma depletes it. We find that an increase in the net gamma positioning of dynamic hedgers reduces volatility and increases market stability, whereas a negative gamma positioning increases volatility and makes the market more prone to failure. Price discovery typically worsens when dynamic hedgers become more prevalent, regardless of the sign of their positioning. Our findings imply that steering the net gamma position of dynamic hedgers can be considered a policy instrument to improve market quality, especially for instruments with low liquidity or low traded volume.</p
Biomarkers of coagulation and inflammation in dogs after randomized administration of 6% Hydroxyethyl Starch 130/0.4 or Hartmann’s Solution
Synthetic colloid fluids containing hydroxyethyl starch (HES) have been associated with impairment of coagulation in dogs. It is unknown if HES causes coagulation impairment in dogs with naturally occurring critical illness. This study used banked plasma samples from a blinded, randomized clinical trial comparing HES and balanced isotonic crystalloid for bolus fluid therapy in 39 critically ill dogs. Blood was collected prior to fluid administration and 6, 12, and 24 h thereafter. Coagulation biomarkers measured at each time point included prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen concentration, and the activities of coagulation factors V, VII, VIII, IX, and X, von Willebrand factor antigen, antithrombin, and protein C. Given the links between coagulation and inflammation, cytokine concentrations were also measured, including interleukins 6, 8, 10, and 18, keratinocyte-derived chemokine, and monocyte chemoattractant protein-1. Data were analyzed with linear mixed effects models. No significant treatment-by-time interactions were found for any biomarker, indicating that the pattern of change over time was not modified by treatment. Examining the main effect of time showed significant changes in several coagulation biomarkers and keratinocyte-derived chemokines. This study could not detect evidence of coagulation impairment with HES
Hamiltonian Study of Improved Lattice Gauge Theory in Three Dimensions
A comprehensive analysis of the Symanzik improved anisotropic
three-dimensional U(1) lattice gauge theory in the Hamiltonian limit is made.
Monte Carlo techniques are used to obtain numerical results for the static
potential, ratio of the renormalized and bare anisotropies, the string tension,
lowest glueball masses and the mass ratio. Evidence that rotational symmetry is
established more accurately for the Symanzik improved anisotropic action is
presented. The discretization errors in the static potential and the
renormalization of the bare anisotropy are found to be only a few percent
compared to errors of about 20-25% for the unimproved gauge action. Evidence of
scaling in the string tension, antisymmetric mass gap and the mass ratio is
observed in the weak coupling region and the behaviour is tested against
analytic and numerical results obtained in various other Hamiltonian studies of
the theory. We find that more accurate determination of the scaling
coefficients of the string tension and the antisymmetric mass gap has been
achieved, and the agreement with various other Hamiltonian studies of the
theory is excellent. The improved action is found to give faster convergence to
the continuum limit. Very clear evidence is obtained that in the continuum
limit the glueball ratio approaches exactly 2, as expected in a
theory of free, massive bosons.Comment: 13 pages, 15 figures, submitted to Phys. Rev.
Revisiting glueball wave functions at zero and finite temperature
We study the sizes and thermal properties of glueballs in a three dimensional
compact Abelian gauge model on improved lattice. We predict the radii of and in the units of string tension, or and fm, for the scalar and tensor glueballs, respectively. We perform a well
controlled extrapolation of the radii to the continuum limit and observe that
our results agree with the predicted values. Using Monte Carlo simulations, we
extract the pole-mass of the lowest scalar and tensor glueballs from the
temporal correlators at finite temperature. We see a clear evidence of the
deconfined phase, and the transition appears to be similar to that of the
two-dimensional XY model as expected from universality arguments. Our results
show no significant changes in the glueball wave functions and masses in the
deconfined phase.Comment: 8 pages, 10 figure
Glueballs, gluon condensate, and pure glue QCD below T_c
A quasiparticle description of pure glue QCD thermodynamics at T<T_c is
proposed and compared to recent lattice data. Given that a gas of glueballs
with constant mass cannot quantitatively reproduce the early stages of the
deconfinement phase transition, the problem is to identify a relevant mechanism
leading to the observed sudden increase of the pressure, trace anomaly, etc. It
is shown that the strong decrease of the gluon condensate near T_c combined
with the increasing thermal width of the lightest glueballs might be the
trigger of the phase transition.Comment: 5 pages, 5 figures; analysis refined in v2, explanations added; v3 to
appear in EPJ
A Nonlinear Force-Free Magnetic Field Approximation Suitable for Fast Forward-Fitting to Coronal Loops. I. Theory
We derive an analytical approximation of nonlinear force-free magnetic field
solutions (NLFFF) that can efficiently be used for fast forward-fitting to
solar magnetic data, constrained either by observed line-of-sight magnetograms
and stereoscopically triangulated coronal loops, or by 3D vector-magnetograph
data. The derived NLFFF solutions provide the magnetic field components
, , , the force-free parameter
, the electric current density , and are
accurate to second-order (of the nonlinear force-free -parameter). The
explicit expressions of a force-free field can easily be applied to modeling or
forward-fitting of many coronal phenomena.Comment: Solar Physics (in press), 26 pages, 11 figure
Does the QCD plasma contain propagating gluons?
Comparison of two appropriately chosen screening masses of colour singlet
operators in the pure glue QCD plasma indicates that at sufficiently high
temperature it contains a weakly-interacting massive quasi-particle with the
quantum numbers of the electric gluon. Still in the deconfined phase, but
closer to T_c, the same mass ratio is similar to that at zero temperature,
indicating that the propagating modes are more glueball-like, albeit with a
lower scale for the masses. We observe a continuity between these two regimes.Comment: 4 pages, 3 figure
Glueball Properties at Finite Temperature in SU(3) Anisotropic Lattice QCD
The thermal properties of the glueballs are studied using SU(3) anisotropic
lattice QCD with beta=6.25, the renormalized anisotropy xi=a_s/a_t=4 over the
lattice of the size 20^3\times N_t with N_t = 24, 26, 28, 30, 33, 34, 35, 36,
37, 38, 40, 43, 45, 50, 72 at the quenched level. To construct a suitable
operator on the lattice, we adopt the smearing method, and consider its
physical meaning in terms of the operator size. First, we construct the
temporal correlators G(t) for the 0^{++} and 2^{++} glueballs, using more than
5,000 gauge configurations at each temperature. We then measure the pole-mass
of the thermal glueballs from G(t). For the lowest 0^{++} glueball, we observe
a significant pole-mass reduction of about 300 MeV near T_c or m_G(T\simeq T_c)
\simeq 0.8 m_G(T\sim 0), while its size remains almost unchanged as rho(T)
\simeq 0.4fm. Finally, for completeness, as an attempt to take into account the
effect of thermal width Gamma(T) at finite temperature, we perform a more
general new analysis of G(t) based on its spectral representation. By adopting
the Breit-Wigner form for the spectral function rho(omega), we perform the
best-fit analysis as a straightforward extension to the standard pole-mass
analysis. The result indicates a significant broadening of the peak as Gamma(T)
\sim 300 MeV as well as rather modest reduction of the peak center of about 100
MeV near T_c for the lowest 0^{++} glueball. The temporal correlators of the
color-singlet modes corresponding to these glueballs above T_c are also
investigated.Comment: This is the revised version using more gauge configurations near T_c.
25 pages, Latex2e, 22 figure
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