Noise propagation in urban and industrial areas

Noise propagation in streets and the discrepancies between theoretical analyses and field measurements are discussed. A cell-model is used to estimate the general background level of noise due to vehicular sources distributed over the urban area

Quarkonium spin structure in lattice NRQCD

Numerical simulations of the quarkonium spin splittings are done in the framework of lattice nonrelativistic quantum chromodynamics (NRQCD). At leading order in the velocity expansion the spin splittings are of $O(M_Q v^4)$, where $M_Q$ is the renormalized quark mass and $v^2$ is the mean squared quark velocity. A systematic analysis is done of all next-to-leading order corrections. This includes the addition of $O(M_Q v^6)$ relativistic interactions, and the removal of $O(a^2 M_Q v^4)$ discretization errors in the leading-order interactions. Simulations are done for both S- and P-wave mesons, with a variety of heavy quark actions and over a wide range of lattice spacings. Two prescriptions for the tadpole improvement of the action are also studied in detail: one using the measured value of the average plaquette, the other using the mean link measured in Landau gauge. Next-to-leading order interactions result in a very large reduction in the charmonium splittings, down by about 60% from their values at leading order. There are further indications that the velocity expansion may be poorly convergent for charmonium. Prelimary results show a small correction to the hyperfine splitting in the Upsilon system.Comment: 16 pages, REVTEX v3.1, 5 postscript figures include

Tadpole renormalization and relativistic corrections in lattice NRQCD

We make a comparison of two tadpole renormalization schemes in the context of the quarkonium hyperfine splittings in lattice NRQCD. Improved gauge-field and NRQCD actions are analyzed using the mean-link $u_{0,L}$ in Landau gauge, and using the fourth root of the average plaquette $u_{0,P}$. Simulations are done for $c\bar c$, $b\bar c$, and $b\bar b$ systems. The hyperfine splittings are computed both at leading and at next-to-leading order in the relativistic expansion. Results are obtained at lattice spacings in the range of about 0.14~fm to 0.38~fm. A number of features emerge, all of which favor tadpole renormalization using $u_{0,L}$. This includes much better scaling behavior of the hyperfine splittings in the three quarkonium systems when $u_{0,L}$ is used. We also find that relativistic corrections to the spin splittings are smaller when $u_{0,L}$ is used, particularly for the $c\bar c$ and $b\bar c$ systems. We also see signs of a breakdown in the NRQCD expansion when the bare quark mass falls below about one in lattice units. Simulations with $u_{0,L}$ also appear to be better behaved in this context: the bare quark masses turn out to be larger when $u_{0,L}$ is used, compared to when $u_{0,P}$ is used on lattices with comparable spacings. These results also demonstrate the need to go beyond tree-level tadpole improvement for precision simulations.Comment: 14 pages, 7 figures (minor changes to some phraseology and references

Self-consistent equilibrium of a two-dimensional electron system with a reservoir in a quantizing magnetic field: Analytical approach

An analytical approach has been developed to describe grand canonical equilibrium between a three dimensional (3D) electron system and a two dimensional (2D) one, an energy of which is determined self-consistently with an electron concentration. Main attention is paid to a Landau level (LL) pinning effect. Pinning means a fixation of the LL on a common Fermi level of the 2D and the 3D systems in a finite range of the magnetic field due to an electron transfer from the 2D to the 3D system. A condition and a start of LL pinning has been found for homogeneously broadened LLs. The electronic transfer from the 3D to the 2D system controls an extremely sharp magnetic dependency of an energy of the upper filled LL at integer filling of the LLs. This can cause a significant increase of inhomogeneous broadening of the upper LL that was observed in recent local probe experiments.Comment: 12 pages, 2 figures, revtex

D to K and D to pi semileptonic form factors from Lattice QCD

We present a very high statistics study of D and D_s semileptonic decay form factors on the lattice. We work with MILC N_f=2+1 lattices and use the Highly Improved Staggered Quark action (HISQ) for both the charm and the strange and light valence quarks. We use both scalar and vector currents to determine the form factors f_0(q^2) and f_+(q^2) for a range of D and D_s semileptonic decays, including D to pi and D to K. By using a phased boundary condition we are able to tune accurately to q^2=0 and explore the whole q^2 range allowed by kinematics. We can thus compare the shape in q^2 to that from experiment and extract the CKM matrix element |V_cs|. We show that the form factors are insensitive to the spectator quark: D to K and D_s to eta_s form factors are essentially the same, which is also true for D to pi and D_s to K within 5%. This has important implications when considering the corresponding B/B_s processes.Comment: To appear in the proceedings of The 5th International Workshop on Charm Physics (Charm 2012

Waste heat from the London Underground: an investigation of the potential benefits of integrating heating and cooling

Waste or recoverable heat is a resource that could be cost-effectively exploited by district heating (DH) systems to increase the efficiency of heat supply in buildings. This paper introduces the Bunhill waste heat recovery (WHR) system, a novel scheme that recovers waste energy from a ventilation shaft of the London Underground (LU) transport network. The system is based upon the installation of a heat recovery heat exchanger consisting of cooling coils and a reversible fan; the coils are connected to a heat pump that supplies low-carbon thermal energy to the Bunhill DH network in central London. One particularly important aspect of the Bunhill WHR system is its ability to operate in a way that not only provides heating to the local heat network, but can also simultaneously supply cooled air to the LU tunnels depending on the operation of the reversible fan. The current paper presents the results from an investigation into the benefits of integrating heating and cooling from the perspective of reducing carbon emissions and the levelised costs of energy from the WHR system, whilst also alleviating peak temperatures at nearby LU stations through the cooling provided. The findings of the investigation are presented together with recommendations for further development and future deployment of WHR systems, which not only apply to underground railways but also to other sources of recoverable heat

Precision Charmonium Spectroscopy From Lattice QCD

We present results for Charmonium spectroscopy using Non-Relativistic QCD (NRQCD). For the NRQCD action the leading order spin-dependent and next to leading order spin-independent interactions have been included with tadpole-improved coefficients. We use multi-exponential fits to multiple correlation functions to extract ground and excited $S$ states. Splittings between the lowest $S$, $P$ and $D$ states are given and we have accurate values for the $S$ state hyperfine splitting and the $\chi_c$ fine structure. Agreement with experiment is good - the remaining systematic errors are discussed.Comment: 23 pages uuencoded latex file. Contains figures in late