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1.
Roberto da Silva  Nelson Alves  Jr.   《Physica A》2005,350(2-4):263-276
In this work, a three-state cellular automaton proposed to describe part of a biological immune system is revisited. We obtain the dynamic critical exponent z of the model by means of a recent technique that mixes different initial conditions. Moreover, by using two distinct approaches, we have also calculated the global persistence exponent θg, related to the probability that the order parameter of the model does not change its sign up to time t [P(t)∝t-θg].  相似文献   

2.
SLIM is a large area experiment (440 m2) installed at the Chacaltaya cosmic ray laboratory since 2001, and about 100 m2 at Koksil, Himalaya, since 2003. It is devoted to the search for intermediate mass magnetic monopoles (107–1013 GeV/c2) and nuclearites in the cosmic radiation using stacks of CR-39 and Makrofol nuclear track detectors. In four years of operation it will reach a sensitivity to a flux of about 10-15 cm-2 s-1 sr-1. We present the results of the calibration of CR-39 and Makrofol and the analysis of a first sample of the exposed detector.  相似文献   

3.
For arbitrary interparticle interaction u(r12), the model two-electron atom in the title is shown to be such that the ground-state electron density ρ(r) is determined uniquely by the correlated kinetic energy density tR(r) of the relative motion. Explicit results for tR(r) are presented for the Hookean atom with force constant k=1/4, and also for . Possible relevance of the Hookean atom treatment to the ground state of the helium atom itself is briefly discussed.  相似文献   

4.
Radon alpha activity concentration has been measured in 28 homes in the Erbil Capital-Iraqi Kurdistan region during the autumn season by using time-integrated passive radon dosimeters containing CR-39 solid state nuclear track detectors “SSNTDs”. The radon activity concentrations in these homes range from (10.33–90.34) with an average of . The average absorption effective dose equivalent for a person living in homes for which the investigation were done was found to be , obtained by using an equilibrium factor of 0.5 and an occupancy factor of 0.8. The average lung cancer cases per year per 106 person was found to be 23±12.  相似文献   

5.
We consider the implications from the possibility that the recently observed state X(3872) is a meson–antimeson molecule. We write an effective Lagrangian consistent with the heavy-quark and chiral symmetries needed to describe X(3872). We explore the consequences of the assumption that X(3872) is a molecular bound state of D*0 and mesons for the existence of bound states in the and channels.  相似文献   

6.
Experimental results and theoretical studies show that protons from the hydrogen plasma focus are emitted predominantly in the axial direction. In this work the results of the flux and energy distribution measurements of the axial protons using CR-39 detector are presented. The main purpose of the experiment is to test the suitability of a plasma focus device as a source for (p,) nuclear reactions, especially and .  相似文献   

7.
Manu Mathur   《Physics letters. [Part B]》2006,640(5-6):292-296
We reformulate d-dimensional SU(2) lattice gauge theory in terms of gauge invariant loop state variables by solving the SU(2) Gauss law as well as the corresponding Mandelstam constraints. The loop states satisfying the Gauss law and the Mandelstam constraints in d dimension are explicitly constructed in terms of the SU(2) harmonic oscillator prepotential operators. We show that these mutually independent (orthonormal) loop states carry certain non-negative integer Abelian fluxes over the lattice links and are characterized by 3(d−1) gauge invariant angular momentum quantum numbers per lattice site. Thus, they provide a complete orthonormal loop basis in the physical Hilbert space of the gauge theory. Further, we derive the loop Hamiltonian and show that it counts, creates and annihilates the Abelian fluxes over the plaquettes. The generalization to SU(N) gauge group is discussed.  相似文献   

8.
Usually, the design of the electrodes of fast-transverse-flow CO2 lasers relies more on experimental data than on theoretical analysis. Traditional systems sustain a stable, high-power discharge but the current distribution generates a peaked, non-uniform small-signal-gain pattern. We present a theoretical model suitable for the design of electrodes that achieves a quasi uniform gain distribution. The analysis, based on a two-temperature model and the gas-transport equations, computes the electron density that supports a flat gain pattern. Combining the desired electron density with the electron-balance equations, the model determines the required electric field. The results were used to design a new set of electrodes for a home-made fast transverse flow CO2 laser. A stable, large volume discharge () with very good uniformity was obtained. The resulting gain distribution was registered in a bi-dimensional map. The peak gain rose from , attained with the old electrode set, to with the new one and the gain showed a homogeneous profile.  相似文献   

9.
Recoiling daughters of -decaying U and Th impurities in mica and other minerals produce localised lattice damage: alpha-recoil tracks. The age of a sample can be calculated from the number of tracks per unit volume (NART). To this end, the mica is etched and the etch pits at the sites of recoil-tracks are counted under the optical microscope. Because the measured track densities increase with etching time, NART is calculated from the fitted regression line. A number of problems inherent in this approach are overcome by the etch–anneal–etch and the mirror-image methods. The track densities determined with these methods are independent of etching time. Although both methods need improvement, they hold the potential of a precise determination of NART from a single measurement in future recoil-track dating.  相似文献   

10.
We calculate the wavelength dependence of the ratio of the linear polarization degree to extinction (polarizing efficiency) P(λ)/A(λ) from the ultraviolet to near-infrared. The prolate and oblate particles with aspect ratios from a/b=1.1 up to 10 are assumed to be rotating and partially aligned with the mechanism of paramagnetic relaxation (Davis–Greenstein). Size/shape/orientation effects are analyzed. It is found that the wavelength dependence of P(λ)/A(λ) is mainly determined by the particle composition and size whereas the values of P(λ)/A(λ) depend on the particle shape, degree and direction of alignment.  相似文献   

11.
Final state medium-induced gluon radiation in ultradense nuclear matter is examined and shown to favor large angle emission when compared to vacuum bremsstrahlung due to the suppression of collinear gluons. Perturbative expression for the contribution of its hadronic fragments to the back-to-back particle correlations is derived. It is found that in the limit of large jet energy loss gluon radiation determines the yield and angular distribution of dihadrons to high transverse momenta pT2 of the associated particles. Clear transition from enhancement to suppression of the away-side hadron correlations is established at moderate pT2 and its experimentally accessible features are predicted versus the trigger particle momentum pT1.  相似文献   

12.
In this paper, we will define a quantum operator that performs the standard inversion about the mean only on a subspace of the system (Partial Diffusion Operator). This operator is used together with entanglement in a quantum search algorithm that runs in for searching an unstructured list of size N with M matches such that 1≤MN. We will show that the performance of the algorithm is more reliable than known fixed operators quantum search algorithms especially for multiple matches where we can get a solution after a single iteration with probability over 90% if the number of matches is approximately more than one-third of the search space. We will show that the algorithm will be able to handle the case where the number of matches M is unknown in advance in such that 1≤MN.  相似文献   

13.
The recent measurement by CDF M(Σb)−M(Λb)=192 MeV is in striking agreement with our theoretical prediction M(Σb)−M(Λb)=194 MeV. In addition, the measured splitting agrees well with the predicted splitting of 22 MeV. We point out the connection between these predictions and an effective supersymmetry between mesons and baryons related by replacing a light antiquark by a light diquark. We discuss the theoretical framework behind these predictions and use it to provide additional predictions for the masses of spin- and spin- baryons containing heavy quarks, as well as for magnetic moments of Λb and Λc.  相似文献   

14.
A simple specific pattern of the two 3×3 quark mass matrices is proposed, resulting in a prediction of the CP phase of the charged-current mixing matrix VCKM, i.e., sin21(β)=0.733, which is in remarkable agreement with data, i.e., sin21=0.728±0.056±0.023 from Belle and sin2β=0.722±0.040±0.023 from BaBar. This pattern can be maintained by a discrete family symmetry, an example of which is D7, the symmetry group of the heptagon.  相似文献   

15.
A.G. Ramm   《Physics letters. A》2007,370(5-6):522-527
A method is proposed to create materials with a desired refraction coefficient, possibly negative one. The method consists of embedding into a given material small particles. Given n0(x), the refraction coefficient of the original material in a bounded domain , and a desired refraction coefficient n(x), one calculates the number N(x) of small particles, to be embedded in D around a point xD per unit volume of D, in order that the resulting new material has refraction coefficient n(x).  相似文献   

16.
A device to determine the detection efficiency of CR-39 for alpha particles is presented. A beehive collimator restricted the angle of incidence of alpha particles on a CR-39 sheet, such that the total number of alpha emitters could be determined. This makes it possible to obtain the critical angle of incidence, ΘC, and the maximum angle of incidence resulting in round (diameter ratio <1.100) etch pits, Θmax. In this work, these angles were determined for incidence energies around 7.5 MeV (more specifically 6.1 and 8.8 MeV).  相似文献   

17.
E. Momoniat   《Physics letters. A》2008,372(22):4041-4044
A Fourier point source solution modelling the effect of an impulse on a viscoelastic fluid of second-grade is investigated. By examining the second-moment of a Fourier point source solution we show that for Dt1, where D=ν/ for ν the kinematic viscosity, a viscoelastic parameter and t the time; the fluid undergoes superdiffusion indicating the dominance of the fluids viscoelastic properties. For Dt1 the fluid undergoes classical diffusion indicating that the viscous properties of the fluid are dominating.  相似文献   

18.
Production of f0(1710), a theoretical endeavor of pure scalar glueball state, is studied in detail from exclusive rare B decay within the framework of perturbative QCD. The branching fraction for is estimated to be about 8×10−6, while for it is smaller by roughly an order of magnitude. With the accumulation of almost 1 billion pairs from the BaBar and Belle experiments to date, hunting for a scalar glueball via these rare decay modes should be attainable.  相似文献   

19.
We extend our previous results on small-x resummation in the pure Yang–Mills theory to full QCD with nf quark flavours, with a resummed two-by-two matrix of resummed quark and gluon splitting functions. We also construct the corresponding deep-inelastic coefficient functions, and show how these can be combined with parton densities to give fully resummed deep-inelastic structure functions F2 and FL at the next-to-leading logarithmic level. We discuss how this resummation can be performed in different factorization schemes, including the commonly used scheme. We study the importance of the resummation effects by comparison with fixed-order perturbative results, and we discuss the corresponding renormalization and factorization scale variation uncertainties. We find that for x below 10−2 the resummation effects are comparable in size to the fixed order NNLO corrections, but differ in shape. We finally discuss the phenomenological impact of the small-x resummation, specifically in the extraction of parton distribution from present day experiments and their extrapolation to the kinematics relevant for future colliders such as the LHC.  相似文献   

20.
We show numerically that a Kerr nonlinear system composed of two channel waveguides coupled periodically by circular microresonators can be used as an all optical diode. The diode has low intensity requirements (50 MW/cm2) and compact dimensions (100  m).  相似文献   

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