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Introduction: Two-photon microscopy is the ideal tool to study how signals are processed in the functional brain tissue. However, early raster scanning strategies were inadequate to record fast 3D events like action potentials. Aim: The aim of the authors was to record various neuronal activity patterns with high signal-to-noise ratio in an optical manner. Method: Authors developed new data acquisition methods and microscope hardware. Results: Multiple Line Scanning enables the experimenter to select multiple regions of interests, doing this not just increases repetition speed, but also the signal-to-noise ratio of the fluorescence transients. On the same principle, an acousto-optical deflector based 3D scanning microscope has been developed with a sub-millisecond temporal resolution and a millimeter z-scanning range. Its usability is demonstrated by obtaining 3D optical recordings of action potential backpropagation in several hundred micrometers long neuronal processes of single neurons and by 3D random-access scanning of Ca2+ transients in hundreds of neurons in the mouse visual cortex. Conclusions: Region of interest scanning enables high signal-to-noise ratio and repetition speed, while keeping good depth penetration of the two-photon microscopes. Orv. Hetil., 2015, 156(52), 2120–2126.

Under stress, many crystalline materials exhibit irreversible plastic deformation caused by the motion of lattice dislocations. In plastically deformed microcrystals, internal dislocation avalanches lead to jumps in the stress-strain curves (strain bursts), whereas in macroscopic samples plasticity appears as a smooth process. By combining three-dimensional simulations of the dynamics of interacting dislocations with statistical analysis of the corresponding deformation behavior, we determined the distribution of strain changes during dislocation avalanches and established its dependence on microcrystal size. Our results suggest that for sample dimensions on the micrometer and submicrometer scale, large strain fluctuations may make it difficult to control the resulting shape in a plastic-forming process.

Two-photon microscopy is the ideal tool to study how signals are processed in the functional brain tissue. However, early raster scanning strategies were inadequate to record fast 3D events like action potentials.The aim of the authors was to record various neuronal activity patterns with high signal-to-noise ratio in an optical manner.Authors developed new data acquisition methods and microscope hardware.Multiple Line Scanning enables the experimenter to select multiple regions of interests, doing this not just increases repetition speed, but also the signal-to-noise ratio of the fluorescence transients. On the same principle, an acousto-optical deflector based 3D scanning microscope has been developed with a sub-millisecond temporal resolution and a millimeter z-scanning range. Its usability is demonstrated by obtaining 3D optical recordings of action potential backpropagation in several hundred micrometers long neuronal processes of single neurons and by 3D random-access scanning of Ca(2+) transients in hundreds of neurons in the mouse visual cortex.Region of interest scanning enables high signal-to-noise ratio and repetition speed, while keeping good depth penetration of the two-photon microscopes.

We study spin 1/2 isoscalar and isovector, even and odd parity candidates for the Θ + ( 1540 ) pentaquark particle using large scale lattice QCD simulations. Previous lattice works led to inconclusive results because so far it has not been possible to unambiguously identify the known scattering spectrum and tell whether additionally a genuine pentaquark state also exists. Here we carry out this analysis using several possible wave functions (operators), including spatially non-trivial ones with unit orbital angular momentum. The cross correlator matrix we compute is 14×14 with 60 non-vanishing elements. We can clearly distinguish the lowest scattering state(s) in both parity channels up to above the expected location of the pentaquark, but we find no trace of the latter. We conclude that there are most probably no pentaquark bound states at our quark masses, corresponding to m π = 400 – 630 MeV . However, we cannot rule out the existence of a pentaquark state at the physical quark masses or pentaquarks with a more exotic wave function.

We study spin 1/2 isoscalar and isovector candidates in both parity channels for the recently discovered \Theta^+(1540) pentaquark particle in quenched lattice QCD. Our analysis takes into account all possible uncertainties, such as statistical, finite size and quenching errors when performing the chiral and continuum extrapolations and we have indications that our signal is separated from scattering states. The lowest mass that we find in the I^P=0^- channel is in complete agreement with the experimental value of the \Theta^+ mass. On the other hand, the lowest mass state in the opposite parity I^P=0^+ channel is much higher. Our findings suggests that the parity of the \Theta^+ is negative., Comment: 13 pages, 5 figures. Final version, appeared in JHEP

The relaxation of an initially random arrangement of straight, parallel edge dislocations is studied with discrete dislocation dynamics simulation. The time evolution of several quantities characterising the elastic state of the embedding crystal as well as the correlation and kinematic properties of the dislocations is calculated numerically. With nonlinear curve fitting it is found that these quantities decay as power law functions of time with exponents between 0.5 and 1 meaning that the dynamics of dislocation relaxation is extremely slow.

The method of holotomography was applied to investigate the microstructure of a metal–matrix composite (MMC) consisting of an AA6061 aluminium matrix reinforced with 20 vol.% Al 2 O 3 particles. Various statistical functions characterizing the Al 2 O 3 particles and the matrix were evaluated, which facilitate a better understanding of the correlation between microstructural features and the overall physical properties of the composite. The shape of the particles is approximated by an ellipsoid and their spatial distribution is described in terms of the pair-distribution function of particle centers and the two-point probability functions of the component phases. The investigated statistical functions emphasize the existence of a short-range correlation in the microstructure, which has a correlation length of about two times the average nearest-neighbor distance. To understand better the influence of the particle shape on different statistical descriptors a comparison between the real microstructure and a system of random hard-spheres is presented.

The problem of the collective behavior of straight parallel edge dislocations is investigated. Starting from the equation of motion of individual dislocations a continuum description is derived. It is shown that the influence of the short range dislocation-dislocation interactions on the dislocation dynamics can be well described by a local back stress which scales like the square root of dislocation density plus a non-local diffusion-like term. The value of the corresponding diffusion coefficient is determined numerically, and implications for size effects in plasticity are discussed.

Guinier-Preston zone formation and its effect on plastic instabilities in supersaturated Al-Cu and Al-Zn-Mg-(Cu) alloys were investigated by tensile tests and depth sensing microhardness measurements. It has been shown that plastic instabilities occur in depth sensing microhardness tests performed on supersaturated solid solutions immediately after quenching. In these measurements the load-depth (F-h) indentation curves are not smoothly changing functions, but contain characteristic steps indicating the oscillation of dynamic microhardness. Experimental results show that the occurrence of the instability steps depends on the composition of the alloy. Furthermore, the formation of GP zones suppresses the instabilities, therefore the plastic instabilities disappear at a certain state of decomposition. In this paper some characteristics of the dynamic Vickers indentation instabilities and the effect of GP zone formation on these parameters are investigated. An interpretation is given for the occurrence of instability steps from the aspect that this phenomenon is a form of Portevin-Le Châtelier type plastic instabilities which is associated with a negative strain rate sensitivity. Results of indentation tests are compared with those of constant loading rate tensile tests.

Plastic instabilities were investigated by the depth-sensing microhardness test in binary high-purity Al–Mg alloys with different Mg contents. During the tests the applied load was increased from 0 to 2000 mN at constant loading rate. The instabilities appeared as characteristic steps in the load–depth curves during indentation. It was shown that the occurrence and development of the plastic instabilities depend strongly on the solute content. Furthermore, the plastic instabilities occurred only when the solute concentration was larger than a critical value, C0. From room-temperature tests on Al–Mg alloys, C0 was found to be 0.86 wt% Mg. The critical concentration, which is necessary to get plastic instabilities, was also interpreted theoretically.

In this letter we present the results of our numerical simulations for the finite temperature electroweak phase transition using the SU(2)-Higgs model on four-dimensional lattices at $m_H \approx 80$ GeV. The temporal extension $L_t=2$ is used for asymmetric lattice spacings with an asymmetry parameter $a_s/a_t \approx 4$. The measured thermodynamical quantities (interface tension, jump of the order parameter and latent heat) suggest that the phase transition is of very weakly first order.

We discuss the perturbative running of alpha_s in a model independent way. Our analysis contains data on the hadronic tau decay and hadronic cross sections in e+e- annihilation between 5 GeV and M_Z. We determine the color coefficients and the perturbative beta-function of the strong interaction. The results are in agreement with QCD and rule out the QCD+light gluino scenarios on the 70.8 - 93.0% CL. We combine our method with that of the multi-jet analysis at LEP. The combined result rules out light gluinos at least on the 99.76% CL, provided that nonperturbative effects are not large.

The present baryon asymmetry of the universe has finally been determined at the finite temperature electroweak phase transition. The strength of this transition plays a crucial role. The effective action is presented to higher orders, including wave function correction factors and the fullg4, λ2 effective potential. An upper bound for the Higgs massmH∼70 GeV is concluded for the reliability of the perturbative approach. The finite temperature electroweak, phase transition is studied on the lattice and the most important results of Monte-Carlo simulations are collected.

In our nonperturbative lattice investigation we study the interface tension of the finite-temperature electroweak phase transition. In this analysis the Higgs mass has been chosen to be about $35$ GeV. At the transition point of a finite volume system, tunnelling between the symmetric and the Higgs phase takes place. This phenomenon leads to a splitting of the ground state, which can be used to determine the interface tension. The result obtained this way agrees with the result of the two-coupling method and with the prediction of the perturbative approach., Comment: 10 pages, five figures in uuencoded PS format, Latex + epsf.sty

The possibility of grand unification of the standard model (SM) with fermion spectrum extended to include mirror fermions is examined. SM gauge couplings do not automatically unify. SO(10) grand unification is studied with one intermediate scale. Renormalization group equations (RGE) for fermion Yukawa couplings and the scalar self-coupling are studied numerically at one and two loop level. Strong restrictions for mirror fermion masses are obtained assuming perturbative unification. Mirror masses much smaller than the tree unitarity bounds are required. In particular mirror leptons have to be around 50 GeV. Consistency of the mirror fermion model with LEP precision data is established. A direct search for single production of mirror neutrinos at LEP could exclude or confirm the GUT version of the mirror fermion model., 9 pages, Standard Latex (46kb). 3 figures not included, available by anonymous ftp from hal9000.elte.hu, in directory /arch/pub/result/plot.ps (46kb) or /arch/pub/result/plot.tex (1247kb), standard latex file. DESY 94-006, ITP-Budapest Rep. No. 505

The three generation mirror fermion model is compared with LEP precision and low energy data. While for zero mixing of ordinary and mirror fermions the model is not favoured, for non zero mixing very low $\chi ^2 $ fits have been obtained, in particular when right handed leptonic mixings are small and left handed leptonic mixings are large (of the order of 0.1 radians.), Comment: LateX 9 pages (4 figures available upon request). ITP-Budapest Rep. No. 500

The existence of a well defined yield stress, where a macroscopic piece of crystal begins to plastically flow, has been one of the basic observations of materials science. In contrast to macroscopic samples, in micro- and nanocrystals the strain accumulates in distinct, unpredictable bursts, which makes controlled plastic forming rather difficult. Here we study by simulation, in two and three dimensions, plastic deformation of submicron objects under increasing stress. We show that, while the stress-strain relation of individual samples exhibits jumps, its average and mean deviation still specify a well-defined critical stress, which we identify with the jamming-flowing transition. The statistical background of this phenomenon is analyzed through the velocity distribution of short dislocation segments, revealing a universal cubic decay and an appearance of a shoulder due to dislocation avalanches. Our results can help to understand the jamming-flowing transition exhibited by a series of various physical systems., Comment: 5 pages

We give the nonperturbative phase diagram of the four-dimensional hot electroweak phase transition. A systematic extrapolation $a \to 0$ is done. Our results show that the finite temperature SU(2)-Higgs phase transition is of first order for Higgs-boson masses $m_H, LATTICE98(electroweak), presented by Z. Fodor. Latex, 3 pages, 3 figu res. Comment line changed

We study the relaxation dynamics of systems of straight, parallel crystal dislocations, starting from initially random and uncorrelated positions of the individual dislocations. A scaling model of the relaxation process is constructed by considering the gradual extinction of the initial density fluctuations present in the system. The model is validated by ensemble simulations of the discrete dynamics of dislocations. Convincing agreement is found for systems of edge dislocations in single slip irrespective of the net Burgers vector of the dislocation system. It is also demonstrated that the model does not work in multiple slip geometries., 25 pages, 11 figures; submitted to Journal of Statistical Mechanics: theory and experiment after 2nd round of reference

We study the finite-temperature electroweak phase transition by numerical simulations of the four-dimensional SU(2)-Higgs model on anisotropic lattices with temporal extension $L_t=2$. The physically interesting parameter region of Higgs masses near 80 GeV is reached, and recent results on some thermodynamic quantities are presented.

We study spin 1/2 isoscalar and isovector, even and odd parity candidates for the Θ+(1540) pentaquark particle using large scale lattice QCD simulations. Previous lattice works led to inconclusive results because so far it has not been possible to unambiguously identify the known scattering spectrum and tell whether additionally a genuine pentaquark state also exists. Here we carry out this analysis using several possible wave functions (operators), including spatially non-trivial ones with unit orbital angular momentum. The cross correlator matrix we compute is 14×14 with 60 non-vanishing elements. We can clearly distinguish the lowest scattering state(s) in both parity channels up to above the expected location of the pentaquark, but we find no trace of the latter. We conclude that there are most probably no pentaquark bound states at our quark masses, corresponding to mπ =400–630 MeV. However, we cannot rule out the existence of a pentaquark state at the physical quark masses or pentaquarks with a more exotic wave function.

We study spin 1/2 isoscalar and isovector, even and odd parity candidates for the $\Theta^+(1540)$ pentaquark particle using large scale lattice QCD simulations. Previous lattice works led to inconclusive results because so far it has not been possible to unambiguously identify the known scattering spectrum and tell whether additionally a genuine pentaquark state also exists. Here we carry out this analysis using several possible wave functions (operators). Linear combinations of those have a good chance of spanning both the scattering and pentaquark states. Our operator basis is the largest in the literature, and it also includes spatially non-trivial ones with unit orbital angular momentum. The cross correlator we compute is 14$\times$14 with 60 non-vanishing elements. We can clearly distinguish the lowest scattering state(s) in both parity channels up to above the expected location of the pentaquark, but we find no trace of the latter. Based on that we conclude that there are most probably no pentaquark bound states at our quark masses, corresponding to $m_\pi$=400--630 MeV. However, we cannot rule out the existence of a pentaquark state at the physical quark mass corresponding to $m_\pi$=135 MeV or pentaquarks with a more exotic wave function., Comment: 18 pages, 2 figures

The probability distribution of the internal shear stress generated by systems of straight, parallel edge dislocations is studied. The stress distribution functions of randomly distributed dipoles and walls are calculated analytically. The stress distribution function of relaxed systems is also calculated analytically assuming relaxed configurations to be made up of uncorrelated perfect dipoles and walls. The resulting relaxed stress distribution function is compared to numerical simulations.

We present N_t=4 lattice results for the equation of state of 2+1 flavour staggered, dynamical QCD at finite temperature and chemical potential. We use the overlap improving multi-parameter reweighting technique to extend the equation of state for non-vanishing chemical potentials. The results are obtained along the line of constant physics. Our physical parameters extend in temperature and baryon chemical potential upto \approx 500-600 MeV., Comment: 13 pages 9 figures, talk given at Finite Density QCD at Nara, Nara, Japan, 10-12 July 2003

The present work is a summary of the status of lattice pentaquark calculations. After a pedagogic introduction to the basics of lattice hadron spectroscopy we give a critical comparison of results presently available in the literature. Special emphasis is put on presenting some of the possible pitfalls of these calculations. In particular we discuss at length the choice of the hadronic operators and the separation of genuine five-quark states from meson-baryon scattering states., Comment: 13 pages LaTeX, 1 eps figure

We present an N_t=4 lattice study for the equation of state of 2+1 flavour staggered, dynamical QCD at finite temperature and chemical potential. We use the overlap improving multi-parameter reweighting technique to extend the equation of state for non-vanishing chemical potentials. The results are obtained on the line of constant physics and our physical parameters extend in temperature and baryon chemical potential upto \approx 500-600 MeV., Comment: 28 pages, 15 figures

Radiative symmetry breaking is a well known phenomenon in perturbation theory. We study the problem in a non-perturbative framework, i.e. lattice simulations. The example of the bosonic sector of the SU(2)-Higgs model is considered. We determine the minimal scalar mass which turns out to be higher than the mass value given by 1-loop continuum perturbation theory., Comment: Contribution to ICHEP-02, Amsterdam, 24-31 July 2002, 2 pages, 1 figure

We calculate the pressure (p), the energy density (\epsilon) and the baryon density (n_B) of QCD at finite temperatures (T) and chemical potentials (\mu). The recently proposed overlap improving multi-parameter reweighting technique is used to determine observables at nonvanishing chemical potentials. Our results are obtained by studying n_f=2+1 dynamical staggered quarks with semi-realistic masses on N_t=4 lattices., Comment: 3 pages, 6 figures, Lattice2002(nonzerot)

We present the results of our large scale 4-dimensional (4d) lattice simulations for the MSSM electroweak phase transition (EWPT). We carried out infinite volume and continuum limit extrapolations and found a transition whose strength agrees well with perturbation theory. We determined the properties of the bubble wall that are important for a successful baryogenesis., 5 pages, 3figures. Talk presented at Johns Hopkins Workshop on Nonperturbative Quantum Field Theory Methods and their Applications (19-21 August 2000.)

Lattice results show no standard model ISM) electroweak phase transition (EWPT) for Higgs masses approximate to 72 GeV. which is below the present experimental limit. perturbation theory and 3-dimensional simulations indicate an EWPT in the minimal supersymmetric SM (MSSM) that is strong enough fur baryogenesis up to m(h) approximate to 105 GeV. In this Letter we present the results of our large scale 4-dimensional MSSM EWPT simulations. We carried out infinite volume and continuum limits and found a transition whose strength agrees well with perturbation theory, allowing MSSM electroweak baryogenesis at least up to m(h) = 103 +/- 4 GeV. We determined the properties of the bubble wall.

The goal of the Poor Man’s Supercomputer (PMS) project is to construct a cost effective, scalable, fast parallel computer to perform numerical calculations of physical problems that can be implemented on a lattice with nearest neighbour interactions. Our first implementation of PMS was tested by Lattice Gauge Theory simulations. We obtained 3$/Mflop price-to-sustained performance ratio for double precision operations.

We briefly describe the Poor Man's Supercomputer (PMS) project carried out at Eotvos University, Budapest. The goal was to develop a cost effective, scalable, fast parallel computer to perform numerical calculations of physical problems that can be implemented on a lattice with nearest neighbour interactions. To this end we developed the PMS architecture using PC components and designed a special, low cost communication hardware and the driver software for Linux OS. Our first implementation of PMS includes 32 nodes (PMS1). The performance of PMS1 was tested by Lattice Gauge Theory simulations. Using SU(3) pure gauge theory or bosonic MSSM on PMS1 we obtained 3$/Mflop and 0.45$Mflop price-to-sustained performance for double and single precision operations, respectively. The design of the special hardware and the communication driver are freely available upon request for non-profit organizations., Latex, 13 pages, 6 figures included, minor additions, typos corrected

We present a one-loop calculation of the static potential in the SU(2)-Higgs model. The connection to the coupling constant definition used in lattice simulations is clarified. The consequences in comparing lattice simulations and perturbative results for finite temperature applications are explored., 11 pages, 4 eps figures, LaTeX

We study the first-order finite-temperature electroweak phase transition of the SU(2) gauge-Higgs model defined on a 4-dimensional isotropic lattice with temporal extension N_t=2. Finite-size scaling study of Lee-Yang zeros yields the value of the Higgs self coupling of the endpoint at lambda_c=0.00116(16). An independent analysis of Binder cumulant gives a consistent value for the endpoint. Combined with our zero-temperature measurement of Higgs and W boson masses, this leads to M_{H,c}=73.3 +- 6.4 GeV for the critical Higgs boson mass beyond which the electroweak transition turns into a crossover., 17 pages, 9 EPS figures, revtex and epsf

The running of the strong coupling constant, R e+− , R z and R τ is studied on the three-loop level. Based on experimental data of R e+− , R z and R τ and the LEP multijet analysis, the light gluino scenario is excluded to 99.97% CL (window I) and 99.89% CL (window III).

We give the nonperturbative phase diagram of the four-dimensional hot electroweak phase transition. The Monte-Carlo analysis is done on lattices with different lattice spacings ($a$). A systematic extrapolation $a \to 0$ is done. Our results show that the finite temperature SU(2)-Higgs phase transition is of first order for Higgs-boson masses $m_H, Latex, 7 pages, 4 figures

We present a calculation of the O(g^2,\lambda) perturbative corrections to the coupling anisotropies of the SU(2)-Higgs model on lattices with asymmetric lattice spacings. These corrections are obtained by a one-loop calculation requiring the rotational invariance of the gauge and Higgs boson propagators in the continuum limit. The coupling anisotropies are also determined from numerical simulations of the model on appropriate lattices. The one-loop perturbation theory and the simulation results agree with high accuracy. It is demonstrated that rotational invariance is also restored for the static potential determined from space-space and space-time Wilson loops., Comment: 27pages, Latex, 7 figures (7 eps, 3 ps files), correction of misprints

We calculate the ${\cal O}(g^2,\lambda)$ corrections to the coupling anisotropies of the SU(2)-Higgs model on lattices with asymmetric lattice spacings. These corrections are obtained by a one-loop calculation requiring the rotational invariance of the gauge- and Higgs-boson propagators in the continuum limit., Comment: 8 pages, latex, uses epsfig.sty, 5 postscript figures included

The finite temperature phase transition in the SU(2) Higgs model at a Higgs boson mass $M_H \simeq 34$ GeV is studied in numerical simulations on four-dimensional lattices with time-like extensions up to $L_t=5$. The effects of the finite volume and finite lattice spacing on masses and couplings are studied in detail. The errors due to uncertainties in the critical hopping parameter are estimated. The thermodynamics of the electroweak plasma near the phase transition is investigated by determining the relation between energy density and pressure., latex2e, 32 pages, 11 figures with epsfig; A few comments and a new table are added

We present results obtained from a numerical investigation of the electroweak phase transition in the SU(2)-Higgs model. The simulations are performed at two values of the Higgs boson mass, $M_H\approx 20$ GeV and $M_H\approx 50$ GeV. While the phase transition is of strongly first order at the smaller value of the Higgs mass it weakens rapidly when the Higgs mass is increased. This is in qualitative agreement with perturbation theory as the comparison of various physical quantities shows., 6pages, contribution to LATTICE '94, uuencode Latex file and 3 figs

The new contributions to the electron (muon) anomalous magnetic moment arising in mirror fermion theories have been calculated. Imposing the experimental constraint lowers the current upper bound on the ordinary - mirror lepton mixing angles by a factor of 50 making predictions for mirror lepton production at HERA undetectably small. A way out is to allow for different mixing angles of the L and R field components. Choosing very small right mixing angles compatibility with the anomalous magnetic moment measurement may be easily maintained, while choosing left mixing angles close to the upper limits yields still reasonable HERA cross-sections., Comment: 10 pages, 2 figures (not included), Latex file; ITP-BUDAPEST REPORT NO. 487

Two contributions are summarized. The first is on a QCD calculation of the triple energy correlation near the phase space limit. The second / author Z. Fodor/ is on methods for finding the triple gluon vertex already at 44 GeV.