物理与天体物理最新文献

Phase-sensitive Fourier-domain optical coherence tomography (FD-OCT) enables in-vivo, label-free imaging of cellular movements with detection sensitivity down to the nanometer scale, and it is widely employed in emerging functional imaging modalities, such as optoretinography (ORG), Doppler OCT, and optical coherence elastography. However, when imaging tissue dynamics in vivo, inter-frame displacement introduces decorrelation noise that compromises motion detection performance, particularly in terms of sensitivity and accuracy. Here, we demonstrate that the displacement-related decorrelation noise in FD-OCT can be accurately corrected by restoring the initial sampling points using our proposed Phase-Restoring Subpixel Image Registration (PRESIR) method. Derived from a general FD-OCT model, the PRESIR method enables translational shifting of complex-valued OCT images over arbitrary displacements with subpixel precision, while accurately restoring phase components. Unlike conventional approaches that shift OCT images either in the spatial domain at the pixel level or in the spatial frequency domain for subpixel correction, our method reconstructs OCT images by correcting axial displacement in the spectral domain (k domain) and lateral displacement in the spatial frequency domain. We validated the PRESIR method through simulations, phantom experiments, and in-vivo ORG in both rodents and human subjects. Our approach significantly reduced decorrelation noise during the imaging of moving samples, achieving phase sensitivity close to the fundamental limit determined by the signal-to-noise ratio.

Cauchy matrix approach is developed to construct the nonisospectral and variable-coefficient equations and study their integrability. We derive the nonisospectral and variable-coefficient Kadomtsev–Petviashvili ( n-vcKP) equation, which includes the standard KP equation and the nonisospectral and variable-coefficient KdV equation as special cases. The connection of the (tau) function of the n-vcKP equation with the Cauchy matrix approach is clarified. The Lax pair for the n-vcKP equation is derived in a systematic way. Two types of exact solutions are found by solving the corresponding Sylvester equation.

The source OGLE-BLG-DN-0064 (hereafter OGLE64) was classified as a potential dwarf nova based on its regular outburst activity revealed by the OGLE optical survey. In this paper we investigate the X-ray and optical emissions from the source OGLE64 based on archival Chandra and Swift X-ray data and our optical observations with the 6-m BTA telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences. OGLE64 shows an X-ray luminosity (L_{X}approx 1.6times 10^{32}) erg s({}^{-1}) and a high X-ray-to-optical flux ratio (F_{X}/F_{textrm{opt}}approx 1.5) typical for accreting white dwarfs. The X-ray spectrum of OGLE64 is better fitted by the models of a power law with a photon index (Gammaapprox 1.9) and an optically thin plasma with a temperature (kTapprox 6.4) keV. The optical spectrum shows hydrogen and neutral helium emission lines in some of which a double-peaked structure is observed. An analysis of the outburst activity of OGLE64 based on data from the OGLE, ZTF, ATLAS, and ASAS-SN optical surveys has revealed superoutbursts with a characteristic supercycle (P_{textrm{super}}approx 400) days. We found no significant variability in either the X-ray or optical light curves of OGLE64 that could be associated with the change in the visibility conditions for the emitting regions at different orbital phases. Our estimates of the orbital period of the system by indirect methods show that the period probably lies in the range (P_{textrm{orb}}sim 1.5{-}3.5) h. The properties of the X-ray and optical emissions from OGLE64 lead us to conclude that the system is an SU UMa-type dwarf nova.

A sample of plasma density values in a thermonuclear facility is studied. On the basis of discrete analogues of heterogeneous processes and memory flow phenomenology, we construct a class of stochastic processes modeling space–time nonlocality taking the spatial heterogeneity into account. A methodology for processing experimental data is proposed that allows establishing a correspondence between this sample of plasma density values and the class of stochastic processes. A physical interpretation of the nonlocality parameters and the heterogeneity parameter is described.

The spectral and photometric studies of the cataclysmic variable Gaia 19cwm (or ZTF19aamkwxk) have been performed. Based on the analysis of long-term variability, it is concluded that the object belongs to WZ Sge type stars. The light curves show eclipses recurring with an orbital period of (86.32048pm 0.00005) min, as well as an out-of-eclipse variability with a period of ({approx}6.45) min. The latter period is stable for ({sim}4) years and appears to correspond to the rotation of a magnetic white dwarf, i.e., Gaia 19cwm is an intermediate polar. The Gaia 19cwm spectra show photospheric lines of the white dwarf, and Doppler tomograms demonstrate the presence of an accretion disk and a hot spot. Analysis of the eclipse light curve gives an estimates of the white dwarf mass (M_{1}=0.66pm 0.06) (M_{odot}), the donor mass (M_{2}=0.073pm 0.015) (M_{odot}), and the orbital inclination (i=83.8^{circ}pm 1.1^{circ}). Modeling of the spectral energy distribution gives the white dwarf temperature of (T_{textrm{eff}}approx 13,000) K. The X-ray luminosity (L_{X}=(1.6pm 0.3)times 10^{31}) erg/s allows to assign Gaia 19cwm to a small group of low-luminosity intermediate polars.

We consider the effect of (T kern0.9ptoverline{vphantom{T}kern6.0pt}kern-6.9pt T )-deformations in conformal field theories within the perturbation theory. A dimensional regularization scheme is used for a perturbative calculation of the contribution of the (T kern0.9ptoverline{vphantom{T}kern6.0pt}kern-6.9pt T )-deformation to the correlation functions of primary fields of conformal field theory. Renormalization of fields in the case of a two-point correlation function is presented.