Probing negative dimensional integration: two-loop covariant vertex and one-loop light-cone integrals

Negative dimensional integration method (NDIM) seems to be a very promising technique for evaluating massless and/or massive Feynman diagrams. It is unique in the sense that the method gives solutions in different regions of external momenta simultaneously. Moreover, it is a technique whereby the difficulties associated with performing parametric integrals in the standard approach are transferred to a simpler solving of a system of linear algebraic equations, thanks to the polynomial character of the relevant integrands. We employ this method to evaluate a scalar integral for a massless two-loop three-point vertex with all the external legs off-shell, and consider several special cases for it, yielding results, even for distinct simpler diagrams. We also consider the possibility of NDIM in non-covariant gauges such as the light-cone gauge and do some illustrative calculations, showing that for one-degree violation of covariance (i.e., one external, gauge-breaking, light-like vector $n_{\mu}$) the ensuing results are concordant with the ones obtained via either the usual dimensional regularization technique, or the use of principal value prescription for the gauge dependent pole, while for two-degree violation of covariance --- i.e., two external, light-like vectors $n_{\mu}$, the gauge-breaking one, and (its dual) $n^{\ast}_{\mu}$ --- the ensuing results are concordant with the ones obtained via causal constraints or the use of the so-called generalized Mandelstam-Leibbrandt prescription.Comment: 17 pages, 3 ps figures, Revte

Nonlinear magnetic susceptibility and aging phenomena in reentrant ferromagnet: Cu0.2_{0.2}Co0.8_{0.8}Cl2_{2}-FeCl3_{3} graphite bi-intercalation compound

Linear and nonlinear dynamic properties of a reentrant ferromagnet Cu$_{0.2}$Co$_{0.8}$Cl$_{2}$-FeCl$_{3}$ graphite bi-intercalation compound are studied using AC and DC magnetic susceptibility. This compound undergoes successive phase transitions at the transition temperatures $T_{h}$ (= 16 K), $T_{c}$ (= 9.7 K), and $T_{RSG}$ (= 3.5 K). The static and dynamic behaviors of the reentrant spin glass phase below $T_{RSG}$ are characterized by those of normal spin glass phase with critical exponent $\beta$ = 0.57 $\pm$ 0.10, a dynamic critical exponent $x$ = 8.5 $\pm$ 1.8, and an exponent $p$ (= 1.55 $\pm$ 0.13) for the de Almeida -Thouless line. A prominent nonlinear susceptibility is observed between $T_{RSG}$ and $T_{c}$ and around $T_{h}$, suggesting a chaotic nature of the ferromagnetic phase ($T_{RSG} \leq T \leq T_{c}$) and the helical spin ordered phase ($T_{c} \leq T \leq T_{h}$). The aging phenomena are observed both in the RSG and FM phases, with the same qualitative features as in normal spin glasses. The aging of zero-field cooled magnetization indicates a drastic change of relaxation mechanism below and above $T_{RSG}$. The time dependence of the absorption $\chi^{\prime \prime}$ is described by a power law form ($\approx t^{-b^{\prime \prime}}$) in the ferromagnetic phase, where $b^{\prime \prime} \approx 0.074 \pm 0.016$ at $f$ = 0.05 Hz and $T$ = 7 K. No $\omega t$-scaling law for $\chi^{\prime \prime}$ [$\approx (\omega t)^{-b^{\prime \prime}}$] is observed.Comment: 14 pages, 16 figures, and 2 table

An easy way to solve two-loop vertex integrals

Negative dimensional integration is a step further dimensional regularization ideas. In this approach, based on the principle of analytic continuation, Feynman integrals are polynomial ones and for this reason very simple to handle, contrary to the usual parametric ones. The result of the integral worked out in $D<0$ must be analytically continued again --- of course --- to real physical world, $D>0$, and this step presents no difficulties. We consider four two-loop three-point vertex diagrams with arbitrary exponents of propagators and dimension. These original results give the correct well-known particular cases where the exponents of propagators are equal to unity.Comment: 13 pages, LaTeX, 4 figures, misprints correcte

Dynamic scaling and aging phenomena in short-range Ising spin glass: Cu0.5_{0.5}Co0.5_{0.5}Cl2_{2}-FeCl3_{3} graphite bi-intercalation compound

Static and dynamic behavior of short-range Ising-spin glass Cu$_{0.5}$Co$_{0.5}$Cl$_{2}$-FeCl$_{3}$ graphite bi-intercalation compounds (GBIC) has been studied with SQUID DC and AC magnetic susceptibility. The $T$ dependence of the zero-field relaxation time $\tau$ above a spin-freezing temperature $T_{g}$ (= 3.92 $\pm$ 0.11 K) is well described by critical slowing down. The absorption $\chi^{\prime\prime}$ below $T_{g}$ decreases with increasing angular frequency $\omega$, which is in contrast to the case of 3D Ising spin glass. The dynamic freezing temperature $T_{f}(H,\omega)$ at which d$M_{FC}(T,H)/$d$H=\chi^{\prime}(T,H=0,\omega)$, is determined as a function of frequency (0.01 Hz $\leq \omega/2\pi \leq$ 1 kHz) and magnetic field (0 $\leq H \leq$ 5 kOe). The dynamic scaling analysis of the relaxation time $\tau(T,H)$ defined as $\tau = 1/\omega$ at $T = T_{f}(H,\omega)$ suggests the absence of SG phase in the presence of $H$ (at least above 100 Oe). Dynamic scaling analysis of $\chi^{\prime \prime}(T, \omega)$ and $\tau(T,H)$ near $T_{g}$ leads to the critical exponents ($\beta$ = 0.36 $\pm$ 0.03, $\gamma$ = 3.5 $\pm$ 0.4, $\nu$ = 1.4 $\pm$ 0.2, $z$ = 6.6 $\pm$ 1.2, $\psi$ = 0.24 $\pm$ 0.02, and $\theta$ = 0.13 $\pm$ 0.02). The aging phenomenon is studied through the absorption $\chi^{\prime \prime}(\omega, t)$ below $T_{g}$. It obeys a $(\omega t)^{-b^{\prime \prime}}$ power-law decay with an exponent $b^{\prime \prime}\approx 0.15 - 0.2$. The rejuvenation effect is also observed under sufficiently large (temperature and magnetic-field) perturbations.Comment: 14 pages, 19 figures; to be published in Phys. Rev. B (September 1, 2003

Formation mechanism of electrical discharge TiC-Fe composite coatings

Comparison of electric discharge (ED) processed single deposit and continuum TiC-Fe cermet coatings, formed from a sacrificial powder metallurgy TiC tool electrode at negative polarity, on 304 stainless steel, provided insight into the ED coating (EDC) formation mechanism. A deposit from a single spark event was dominated by TiC, phase separated from a ∼2 wt% Fe matrix, with strongly aligned grains and banded microstructure, indicative of solidification from the coating/substrate interface. Conversely, a continuum coating, subjected to ∼200 spark events per location, exhibited a more complex, banded microstructure, with a mixture of equiaxed and columnar TiC grains within a ∼30 wt% Fe-based matrix, along with some concentrations of carbon from the oil dielectric. It is considered that each sparking event remelts previously solidified coating material, with or without further TiC particle incorporation, leading to gradual TiC dilution and the development of a TiC-Fe composite coating with increasing levels of substrate material forming the matrix

Electron interference and entanglement in coupled 1D systems with noise

We estimate the role of noise in the formation of entanglement and in the appearance of single- and two-electron interference in systems of coupled one-dimensional channels semiconductors. Two cases are considered: a single-particle interferometer and a two-particle interferometer exploiting Coulomb interaction. In both of them, environmental noise yields a randomization of the carrier phases. Our results assess how that the complementarity relation linking single-particle behavior to nonlocal quantities, such as entanglement and environment-induced decoherence, acts in electron interferometry. We show that, in a experimental implementation of the setups examined, one- and two-electron detection probability at the output drains can be used to evaluate the decoherence phenomena and the degree of entanglement.Comment: 12 pages, 6 figures. v2: added some references and corrected tex

Chiral three-nucleon forces and bound excited states in neutron-rich oxygen isotopes

We study the spectra of neutron-rich oxygen isotopes based on chiral two- and three-nucleon interactions. First, we benchmark our many-body approach by comparing ground-state energies to coupled-cluster results for the same two-nucleon interaction, with overall good agreement. We then calculate bound excited states in 21,22,23O, focusing on the role of three-nucleon forces, in the standard sd shell and an extended sdf7/2p3/2 valence space. Chiral three-nucleon forces provide important one- and two-body contributions between valence neutrons. We find that both these contributions and an extended valence space are necessary to reproduce key signatures of novel shell evolution, such as the N = 14 magic number and the low-lying states in 21O and 23O, which are too compressed with two-nucleon interactions only. For the extended space calculations, this presents first work based on nuclear forces without adjustments. Future work is needed and open questions are discussed.Comment: 6 pages, 4 figures, published versio

Effect of a magnetic field on the spin- and charge-density wave order in La1.45Nd0.4Sr0.15CuO4

The spin-density wave (SDW) and charge-density wave (CDW) order in superconducting La1.45Nd0.4Sr0.15CuO4 were studied under an applied magnetic field using neutron and X-ray diffraction techniques. In zero field, incommensurate (IC) SDW order appears below ~ 40 K, which is characterized by neutron diffraction peaks at (1/2 +/- 0.134, 1/2 +/- 0.134, 0). The intensity of these IC peaks increases rapidly below T_Nd ~ 8 K due to an ordering of the Nd^3+ spins. The application of a 1 T magnetic field parallel to the c-axis markedly diminishes the intensity below T_Nd, while only a slight decrease in intensity is observed at higher temperatures for fields up to 7 T. Our interpretation is that the c-axis field suppresses the parasitic Nd^3+ spin order at the incommensurate wave vector without disturbing the stripe order of Cu^2+ spins. Consistent with this picture, the CDW order, which appears below 60 K, shows no change for magnetic fields up to 4 T. These results stand in contrast to the significant field-induced enhancement of the SDW order observed in superconducting La2-xSrxCuO4 with x ~ 0.12 and stage-4 La2CuO4+y. The differences can be understood in terms of the relative volume fraction exhibiting stripe order in zero field, and the collective results are consistent with the idea that suppression of superconductivity by vortices nucleates local patches of stripe order.Comment: 7 pages, 5 figure

Measurement of the cosmic microwave background polarization lensing power spectrum from two years of POLARBEAR data

We present a measurement of the gravitational lensing deflection power spectrum reconstructed with two seasons of cosmic microwave background polarization data from the POLARBEAR experiment. Observations were taken at 150 GHz from 2012 to 2014 and surveyed three patches of sky totaling 30 square degrees. We test the consistency of the lensing spectrum with a cold dark matter cosmology and reject the no-lensing hypothesis at a confidence of 10.9σ, including statistical and systematic uncertainties. We observe a value of AL = 1.33 ± 0.32 (statistical) ±0.02 (systematic) ±0.07 (foreground) using all polarization lensing estimators, which corresponds to a 24% accurate measurement of the lensing amplitude. Compared to the analysis of the first- year data, we have improved the breadth of both the suite of null tests and the error terms included in the estimation of systematic contamination

Calibration of Super-Kamiokande Using an Electron Linac

In order to calibrate the Super-Kamiokande experiment for solar neutrino measurements, a linear accelerator (LINAC) for electrons was installed at the detector. LINAC data were taken at various positions in the detector volume, tracking the detector response in the variables relevant to solar neutrino analysis. In particular, the absolute energy scale is now known with less than 1 percent uncertainty.Comment: 24 pages, 16 figures, Submitted to NIM