Experimental investigation of active local blowing on the aerodynamic noise reduction of a circular cylinder

The strategic implementation of local blowing (LB) around a circular cylinder within a uniformflow has demonstrated its capacity to effectively suppress aerodynamic noise under specific blowingconditions. This study aimed to comprehend the underlying mechanism driving noise reductionthrough the synchronisation of far-field noise with surface pressure fluctuations, which were measured at various peripheral angles. The parameters under examination for LB were the angle of blowing in relation to the freestream flow (θb) and the equivalent momentum coefficient (Cµ). A dedicated series of chambers were employed to facilitate LB at θb = ±41◦, ±90◦, ±131◦, and 180◦across the ranges of Cµ = 0.007–0.036 (Re = 0.7 × 105) and Cµ = 0.003–0.016 (Re = 1.04 × 105).Notably, LB at θb = ±41◦ and 180◦exhibited a remarkable reduction in tonal noise within theCµ range of 0.007 to 0.036. Despite this achievement, the most optimal overall sound pressurelevel was achieved at θb = 180◦. It was determined that the dissimilarity in noise reductionamong these LB cases was attributed to additional high-frequency noise generated by the blowing technique. The connection between the near- and far-field signals was established through recordedcoherence values. The investigation highlighted that surface pressure fluctuations initiated byvortex shedding in the pre- and post-separation regions, particularly at the fundamental vortexshedding frequency, had the most significant impact on far-field noise. The attenuation of suchsurface pressure fluctuations played a pivotal role in tonal noise reduction by LB, as evidenced bynotable reductions in lift fluctuations and the absence of amplitude modulation in both the time and frequency domains

Faithful remote state preparation using finite classical bits and a non-maximally entangled state

We present many ensembles of states that can be remotely prepared by using minimum classical bits from Alice to Bob and their previously shared entangled state and prove that we have found all the ensembles in two-dimensional case. Furthermore we show that any pure quantum state can be remotely and faithfully prepared by using finite classical bits from Alice to Bob and their previously shared nonmaximally entangled state though no faithful quantum teleportation protocols can be achieved by using a nonmaximally entangled state.Comment: 6 page

Nonleptonic Weak Decays of Bottom Baryons

Cabibbo-allowed two-body hadronic weak decays of bottom baryons are analyzed. Contrary to the charmed baryon sector, many channels of bottom baryon decays proceed only through the external or internal W-emission diagrams. Moreover, W-exchange is likely to be suppressed in the bottom baryon sector. Consequently, the factorization approach suffices to describe most of the Cabibbo-allowed bottom baryon decays. We use the nonrelativistic quark model to evaluate heavy-to-heavy and heavy-to-light baryon form factors at zero recoil. When applied to the heavy quark limit, the quark model results do satisfy all the constraints imposed by heavy quark symmetry. The decay rates and up-down asymmetries for bottom baryons decaying into $(1/2)^++P(V)$ and $(3/2)^++P(V)$ are calculated. It is found that the up-down asymmetry is negative except for $\Omega_b \to (1/2)^++P(V)$ decay and for decay modes with $\psi'$ in the final state. The prediction $B(\Lambda_b \to J/\psi\Lambda)=1.6 \times 10^{-4}$ for $|V_{cb}|=0.038$ is consistent with the recent CDF measurement. We also present estimates for $\Omega_c \to (3/2)^++P(V)$ decays and compare with various model calculations.Comment: 24 pages, to appear in Phys. Rev. Uncertainties with form factor q^2 dependence are discusse

Nucleon-nucleon momentum correlation function for light nuclei

Nucleon-nucleon momentum correlation function have been presented for nuclear reactions with neutron-rich or proton-rich projectiles using a nuclear transport theory, namely Isospin-Dependent Quantum Molecular Dynamics model. The relationship between the binding energy of projectiles and the strength of proton-neutron correlation function at small relative momentum has been explored, while proton-proton correlation function shows its sensitivity to the proton density distribution. Those results show that nucleon-nucleon correlation function is useful to reflect some features of the neutron- or proton-halo nuclei and therefore provide a potential tool for the studies of radioactive beam physics.Comment: Talk given at the 18th International IUPAP Conference on Few-Body Problems in Physics (FB18), Santos, Brasil, August 21-26, 2006. To appear in Nucl. Phys.

Two qubits of a W state violate Bell's inequality beyond Cirel'son's bound

It is shown that the correlations between two qubits selected from a trio prepared in a W state violate the Clauser-Horne-Shimony-Holt inequality more than the correlations between two qubits in any quantum state. Such a violation beyond Cirel'son's bound is smaller than the one achieved by two qubits selected from a trio in a Greenberger-Horne-Zeilinger state [A. Cabello, Phys. Rev. Lett. 88, 060403 (2002)]. However, it has the advantage that all local observers can know from their own measurements whether their qubits belongs or not to the selected pair.Comment: REVTeX4, 5 page

Effect of polycrystallinity on the optical properties of highly oriented ZnO grown by pulsed laser deposition

We report the results of photoluminescence and reflectance measurements on highly c-axis oriented polycrystalline ZnO grown by pulsed laser deposition. The samples measured were grown under identical conditions and were annealed in-situ at various temperatures for 10-15 min. The band-edge photoluminescence spectra of the material altered considerably with an increase in grain size, with increased free exciton emission and observable excitonic structure in the reflectance spectra. The green band emission also increased with increasing grain size. A deformation potential analysis of the effect of strain on the exciton energy positions of the A- and B-excitons demonstrated that the experimental exciton energies could not be explained solely in terms of sample strain. We propose that electric fields in the samples due to charge trapping at grain boundaries are responsible for the additional perturbation of the excitons. This interpretation is supported by theoretical estimates of the exciton energy perturbation due to electric fields. The behaviour of the green band in the samples provides additional evidence in favour of our model

Search for Invisible Decays of η\eta and η′\eta^\prime in J/ψ→ϕηJ/\psi \to \phi\eta and ϕη′\phi \eta^\prime

Using a data sample of $58\times 10^6$ $J/\psi$ decays collected with the BES II detector at the BEPC, searches for invisible decays of $\eta$ and $\eta^\prime$ in $J/\psi$ to $\phi\eta$ and $\phi\eta^\prime$ are performed. The $\phi$ signals, which are reconstructed in $K^+K^-$ final states, are used to tag the $\eta$ and $\eta^\prime$ decays. No signals are found for the invisible decays of either $\eta$ or $\eta^\prime$, and upper limits at the 90% confidence level are determined to be $1.65 \times 10^{-3}$ for the ratio $\frac{B(\eta\to \text{invisible})}{B(\eta\to\gamma\gamma)}$ and $6.69\times 10^{-2}$ for $\frac{B(\eta^\prime\to \text{invisible})}{B(\eta^\prime\to\gamma\gamma)}$. These are the first searches for $\eta$ and $\eta^\prime$ decays into invisible final states.Comment: 5 pages, 4 figures; Added references, Corrected typo

Neutron/proton ratio of nucleon emissions as a probe of neutron skin

The dependence between neutron-to-proton yield ratio ($R_{np}$) and neutron skin thickness ($\delta_{np}$) in neutron-rich projectile induced reactions is investigated within the framework of the Isospin-Dependent Quantum Molecular Dynamics (IQMD) model. The density distribution of the Droplet model is embedded in the initialization of the neutron and proton densities in the present IQMD model. By adjusting the diffuseness parameter of neutron density in the Droplet model for the projectile, the relationship between the neutron skin thickness and the corresponding $R_{np}$ in the collisions is obtained. The results show strong linear correlation between $R_{np}$ and $\delta_{np}$ for neutron-rich Ca and Ni isotopes. It is suggested that $R_{np}$ may be used as an experimental observable to extract $\delta_{np}$ for neutron-rich nuclei, which is very significant to the study of the nuclear structure of exotic nuclei and the equation of state (EOS) of asymmetric nuclear matter.Comment: 7 pages, 5 figures; accepted by Phys. Lett.

Observation of Two New N* Peaks in J/psi -> ppi−nˉp pi^- \bar n and pˉπ+n\bar p\pi^+n Decays

The $\pi N$ system in decays of $J/\psi\to\bar NN\pi$ is limited to be isospin 1/2 by isospin conservation. This provides a big advantage in studying $N^*\to \pi N$ compared with $\pi N$ and $\gamma N$ experiments which mix isospin 1/2 and 3/2 for the $\pi N$ system. Using 58 million $J/\psi$ decays collected with the Beijing Electron Positron Collider, more than 100 thousand $J/\psi \to p \pi^- \bar n + c.c.$ events are obtained. Besides two well known $N^*$ peaks at 1500 MeV and 1670 MeV, there are two new, clear $N^*$ peaks in the $p\pi$ invariant mass spectrum around 1360 MeV and 2030 MeV. They are the first direct observation of the $N^*(1440)$ peak and a long-sought "missing" $N^*$ peak above 2 GeV in the $\pi N$ invariant mass spectrum. A simple Breit-Wigner fit gives the mass and width for the $N^*(1440)$ peak as $1358\pm 6 \pm 16$ MeV and $179\pm 26\pm 50$ MeV, and for the new $N^*$ peak above 2 GeV as $2068\pm 3^{+15}_{-40}$ MeV and $165\pm 14\pm 40$ MeV, respectively

Hyperbolic Space Cosmologies

We present a systematic study of accelerating cosmologies obtained from M/string theory compactifications of hyperbolic spaces with time-varying volume. A set of vacuum solutions where the internal space is a product of hyperbolic manifolds is found to give qualitatively the same accelerating four-dimensional FLRW universe behavior as a single hyperbolic space. We also examine the possibility that our universe is a hyperbolic space and provide exact Milne type solutions, as well as intersecting S-brane solutions. When both the usual 4D spacetime and the m-dimensional internal space are hyperbolic, we find eternally accelerating cosmologies for $m\geq 7$, with and without form field backgrounds. In particular, the effective potential for a magnetic field background in the large 3 dimensions is positive definite with a local minimum and thus enhances the eternally accelerating expansion.Comment: 33 pages, 2 figures; v2 refs added; v3 minor change in text, JHEP versio