780 research outputs found
Study of isolated prompt photon production in -Pb collisions for the ALICE kinematics
Prompt photon production is known as a powerful tool for testing perturbative
QCD predictions and also the validity of parton densities in the nucleon and
nuclei especially of the gluon. In this work, we have performed a detailed
study on this subject focusing on the isolated prompt photon production in -Pb collisions at forward rapidity at the LHC. The impact of input nuclear
modifications obtained from different global analyses by various groups on
several quantities has been investigated to estimate the order of magnitude of
the difference between their predictions. We have also studied in detail the
theoretical uncertainties in the results due to various sources. We found that
there is a remarkable difference between the predictions from the nCTEQ15 and
other groups in all ranges of photon transverse momentum . Their differences become more explicit in the calculation of the nuclear
modification ratio and also the yield asymmetry between the forward and
backward rapidities rather than single differential cross sections. We
emphasize that future measurements with ALICE will be very useful not only for
decreasing the uncertainty of the gluon nuclear modification, but also to
accurately determine its central values, especially in the shadowing region.Comment: 12 pages, 10 figure
Approximating the Permanent of a Random Matrix with Vanishing Mean
We show an algorithm for computing the permanent of a random matrix with
vanishing mean in quasi-polynomial time. Among special cases are the Gaussian,
and biased-Bernoulli random matrices with mean 1/lnln(n)^{1/8}. In addition, we
can compute the permanent of a random matrix with mean 1/poly(ln(n)) in time
2^{O(n^{\eps})} for any small constant \eps>0. Our algorithm counters the
intuition that the permanent is hard because of the "sign problem" - namely the
interference between entries of a matrix with different signs. A major open
question then remains whether one can provide an efficient algorithm for random
matrices of mean 1/poly(n), whose conjectured #P-hardness is one of the
baseline assumptions of the BosonSampling paradigm
Approximate unitary -designs by short random quantum circuits using nearest-neighbor and long-range gates
We prove that -depth local random quantum circuits
with two qudit nearest-neighbor gates on a -dimensional lattice with n
qudits are approximate -designs in various measures. These include the
"monomial" measure, meaning that the monomials of a random circuit from this
family have expectation close to the value that would result from the Haar
measure. Previously, the best bound was due to
Brandao-Harrow-Horodecki (BHH) for . We also improve the "scrambling" and
"decoupling" bounds for spatially local random circuits due to Brown and Fawzi.
One consequence of our result is that assuming the polynomial hierarchy (PH)
is infinite and that certain counting problems are -hard on average,
sampling within total variation distance from these circuits is hard for
classical computers. Previously, exact sampling from the outputs of even
constant-depth quantum circuits was known to be hard for classical computers
under the assumption that PH is infinite. However, to show the hardness of
approximate sampling using this strategy requires that the quantum circuits
have a property called "anti-concentration", meaning roughly that the output
has near-maximal entropy. Unitary 2-designs have the desired anti-concentration
property. Thus our result improves the required depth for this level of
anti-concentration from linear depth to a sub-linear value, depending on the
geometry of the interactions. This is relevant to a recent proposal by the
Google Quantum AI group to perform such a sampling task with 49 qubits on a
two-dimensional lattice and confirms their conjecture that depth
suffices for anti-concentration. We also prove that anti-concentration is
possible in depth O(log(n) loglog(n)) using a different model
Coupling between time series: a network view
Recently, the visibility graph has been introduced as a novel view for
analyzing time series, which maps it to a complex network. In this paper, we
introduce new algorithm of visibility, "cross-visibility", which reveals the
conjugation of two coupled time series. The correspondence between the two time
series is mapped to a network, "the cross-visibility graph", to demonstrate the
correlation between them. We applied the algorithm to several correlated and
uncorrelated time series, generated by the linear stationary ARFIMA process.
The results demonstrate that the cross-visibility graph associated with
correlated time series with power-law auto-correlation is scale-free. If the
time series are uncorrelated, the degree distribution of their cross-visibility
network deviates from power-law. For more clarifying the process, we applied
the algorithm to real-world data from the financial trades of two companies,
and observed significant small-scale coupling in their dynamics
THE PROINFLAMMATORY EFFECT OF STRUCTURALLY ALTERED ELASTIC FIBERS IN A HAMSTER MODEL OF COPD EXACERBATION
To further understand the effect of superimposed lung inflammation on COPD, our laboratory developed a hamster model of COPD exacerbations using sequential intratracheal instillations of lipopolysaccharide (LPS) and elastase. Using this model, the superimposed inflammatory effect of LPS on elastase-induced emphysema was studied through morphological and biochemical parameters. Total leukocyte and percent neutrophil count in bronchoalveolar lavage fluid (BALF), and elastin-specific desmosine crosslinks (DID) were measured 48 hours after LPS treatment. Morphometric changes were evaluated with mean linear intercept (MLI) methods, and interstitial elastic fiber and lung surface area measurements 1 week post-LPS treatment. Compared to controls, animals treated with elastase/LPS showed a significant increase in BALF leukocytes (187 vs 47.7 x 104 cells), neutrophils (39 vs 4.8 percent), and free DID levels (182 vs 97 percent). Additionally, MLI was significantly elevated in the elastase/LPS group compared to controls (156.2 vs 81.7micrometer). Due to enhanced splaying and fragmentation of elastic fibers, interstitial elastic fiber surface area was significantly increased in animals treated with elastase/LPS than controls (49 vs 26 percent). On the other hand, lung surface area was decreased in elastase/LPS group compared to controls (17.8 vs 25.5 percent). Furthermore, intratracheal instillations of elastin peptides and LPS demonstrated significant effects on BALF neutrophils, free DID levels and leukocyte chemotactic properties. The results suggest that structural alterations in elastic fibers during exacerbations make them more susceptible to breakdown and may have a proinflammatory effect further accelerating loss of lung parenchyma and function
Non-Classical Symmetry Solutions to the Fitzhugh Nagumo Equation.
In Reaction-Diffusion systems, some parameters can influence the behavior of other parameters in that system. Thus reaction diffusion equations are often used to model the behavior of biological phenomena. The Fitzhugh Nagumo partial differential equation is a reaction diffusion equation that arises both in population genetics and in modeling the transmission of action potentials in the nervous system. In this paper we are interested in finding solutions to this equation. Using Lie groups in particular, we would like to find symmetries of the Fitzhugh Nagumo equation that reduce this non-linear PDE to an Ordinary Differential Equation. In order to accomplish this task, the non-classical method is utilized to find the infinitesimal generator and the invariant surface condition for the subgroup where the solutions for the desired PDE exist. Using the infinitesimal generator and the invariant surface condition, we reduce the PDE to a mildly nonlinear ordinary differential equation that could be explored numerically or perhaps solved in closed form
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