Low frequency random telegraphic noise (RTN) and 1/f noise in the rare-earth manganite Pr0.63_{0.63}Ca0.37_{0.37}MnO3_3 near the charge-ordering transition

We have studied low frequency resistance fluctuations (noise) in a single crystal of the rare earth perovskite manganite Pr$_{0.63}$Ca$_{0.37}$MnO$_3$ which shows a charge ordering transition at a temperature $T_{CO}$ ~ 245K. The noise measurements were made using an ac bias with and without a dc bias current imposed on it. We find that the spectral power $S_V(f)$ contains two components - one broad band 1/f part that exists for all frequency and temperature ranges and a single frequency Lorentzian of frequency $f_c$ which is strongly temperature dependent. The Lorentzian in $S_V(f)$ which appears due to Random telegraphic noise (RTN) as seen in the time series of the fluctuation, is seen in a very narrow temperature window around $T_{CO}$ where it makes the dominating contribution to the fluctuation. When the applied dc bias is increased beyond a certain threshold current density $J_{th}$, the electrical conduction becomes non-linear and one sees appearance of a significant Lorentzian contribution in the spectral power due to RTN. We explain the appearance of the RTN as due to coexisting Charge ordered (CO) and reverse orbitally ordered (ROO) phases which are in dynamical equilibrium over a mesoscopic length scale ($\approx 30nm$) and the kinetics being controlled by an activation barrier $E_{a} ~ 0.45eV. The 1/f noise is low for$T>>T_{CO}$but increases by nearly two orders in a narrow temperature range as$T_{CO}$ is approached from above and the probability distribution function (PDF) deviates strongly from a Gaussian. We explain this behavior as due to approach of charge localization with correlated fluctuators which make the PDF non-Gaussian.Comment: 23 pages, 14 figure

Large deviation for extremes of branching random walk with regularly varying displacements

We consider discrete time branching random walk on real line where the displacements of particles coming from the same parent are allowed to be dependent and jointly regularly varying. Using the one large bunch asymptotics, we derive large deviation for the extremal processes associated to the suitably scaled positions of particles in the nth generation where the genealogical tree satisfies Kesten-Stigum condition. The large deviation limiting measure in this case is identified in terms of the cluster Poisson point process obtained in the underlying weak limit of the point processes. As a consequence of this, we derive large deviation for the rightmost particle in the nth generation giving the heavy-tailed analogue of recent work by Gantert and Höfelsauer [2018]

The Effects of Different Intensity of Thinning on the Development in Scots Pine (Pinus sylvestris L.) Stands in Kazakh Uplands

The search for more accurate methods of predicting the growth and development of forest stands became the most urgent task set for foresters of Kazakhstan to determine the permissible interventions in the natural course of the life of plantings, provide high durability and resilience in forests. The aim of the study was to identify the effects of diameter and density of Scots pine stands of Kazakh Uplands on their growth and productivity and the related productivity of single plantation stands taking into account the conditions of growth and development of internal factors as well as further study of the methodology for assessing the forestry cost-effectiveness and improvement thinning. To achieve this aim, effects of varied felling intensities on Scots pine stands were studied. The most common two forest types in upland Scots pine forests were chosen as permanent sample plots; the dead pine-lichen and moss pine-grass. The results showed that improvement thinning of moderate and severe intensity which are more profitable should be done in Scots pine forests of Kazakh Upland as well as carrying out such thinning increases the yield of the larger logs and increases the value of the left stand

Review of the fast growing forest tree species in Turkey

Los antecedentes de la utilización de especies de crecimiento rápido en Turquía tienen se remontan a 50 años y en los últimos 35-40 años se ha abrodado desde un punto de vista científico. Eucalyptus camaldulensis Dehn., E. grandis W.Hill., Pinus pinaster Ait., P. radiata D. Don., chopos híbridos, algunos clones de Populus deltoides Bartr. ex Marsh. y P. nigra L. son las especies más importantes por su mayor utilización en ensayos de especies, orígenes y en plantaciones. Aunque las especies y orígenes americanas son los más usados en los ensayos, los resultados esperados no han podido ser alcanzados debido al bajo número de clones y orígenes, establecidos en los experimentos que no representan el área de distribución natural. Junto con estas especies, los estudios deberían centrarse en Pinus brutia Ten. que tiene una amplia área de distribución natural en Turquía, elevado potencial y caracteres relacionados con el crecimiento rápido. Además, P. brutia esta considerado como una especie que podría cubrir el déficit de suministro a largo plazo. También, los estudios deberían ocuparse de Fraxinus angustifolia Wahl. subsp. oxycarpa Bieb ex Willd., Salix excelsa J. F. Gmelin., S. Alba L., Pterocarya fraxinifolia Spach. y Alnus glutinosa Gaertn. subsp. barbata (C. A. Mey.) Yalt que fueron probados en varias regiones y mostraron mejores características de crecimiento rápido que otras especies de aliso indígenas._____________________________________The fast growing species have 50 year-old political and 35-40 year-old scientific background in Turkey. Eucalyptus camaldulensis Dehn., E. grandis W.Hill., Pinus pinaster Ait., P. radiata D. Don., hybrid poplars, some clones of Populus deltoides Bartr. ex Marsh. and P. nigra L. are the most important species for obtaining a great deal of progress in species and origin experiments and starting the plantation phase in Turkey. In fast growing species process; although the American species and origins are mostly used, the desired outcomes could not be achived because of establishing the experiments with few number of clones and origins, which didn’t represent the natural distribution area. Along with these species, studies should be focused on Pinus brutia Ten. which has broad natural distribution area in Turkey, improvement potential and fast growing character. Furthermore, P. brutia is evaluated as a species which will close the supply deficit in long run. Also, studies should be performed on Fraxinus angustifolia Wahl. subsp. oxycarpa Bieb ex Willd., Salix excelsa J. F. Gmelin., S. alba L., Pterocarya fraxinifolia Spach. and Alnus glutinosa Gaertn. subsp. barbata (C. A. Mey.) Yalt. which was experimented in regional base and showed the faster growing character than the other indigenous alder species and native species

The Finslerian wormhole models

We present models of wormhole under the Finslerian structure of spacetime. This is a sequel of our previous work (Eur Phys J 75:564, 2015) where we constructed a toy model for compact stars based on the Finslerian spacetime geometry. In the present investigation, a wide variety of solutions are obtained that explore wormhole geometry by considering different choices for the form function and energy density. The solutions, like the previous work, are revealed to be physically interesting and viable models for the explanation of wormholes as far as the background theory and literature are concerned.Comment: 9 pages and 7 figue

Magnetic Field resulting from non-linear electrical transport in single crystals of charge-ordered Pr0.63_{0.63} Ca0.37_{0.37} MnO3_{3}}

In this letter we report that the current induced destabilization of the charge ordered (CO) state in a rare-earth manganite gives rise to regions with ferromagnetic correlation. We did this experiment by measurement of the I-V curves in single crystal of the CO system Pr$_{0.63}$Ca$_{0.37}$MnO$_{3}$ and simultanously measuring the magnetization of the current carrying conductor using a high T$_c$ SQUID working at T = 77K. We have found that the current induced destabilization of the CO state leads to a regime of negative differential resistance which leads to a small enhancement of the magnetization of the sample, indicating ferromagnetically aligned moments.Comment: 4 pages LateX, 4 eps figure

Holography of Gravitational Action Functionals

Einstein-Hilbert (EH) action can be separated into a bulk and a surface term, with a specific ("holographic") relationship between the two, so that either can be used to extract information about the other. The surface term can also be interpreted as the entropy of the horizon in a wide class of spacetimes. Since EH action is likely to just the first term in the derivative expansion of an effective theory, it is interesting to ask whether these features continue to hold for more general gravitational actions. We provide a comprehensive analysis of lagrangians of the form L=Q_a^{bcd}R^a_{bcd}, in which Q_a^{bcd} is a tensor with the symmetries of the curvature tensor, made from metric and curvature tensor and satisfies the condition \nabla_cQ^{abcd}=0, and show that they share these features. The Lanczos-Lovelock lagrangians are a subset of these in which Q^{abcd} is a homogeneous function of the curvature tensor. They are all holographic, in a specific sense of the term, and -- in all these cases -- the surface term can be interpreted as the horizon entropy. The thermodynamics route to gravity, in which the field equations are interpreted as TdS=dE+pdV, seems to have greater degree of validity than the field equations of Einstein gravity itself. The results suggest that the holographic feature of EH action could also serve as a new symmetry principle in constraining the semiclassical corrections to Einstein gravity. The implications are discussed.Comment: revtex 4; 17 pages; no figure

Non-linear electrical conduction and broadband noise in charge-ordered rare earth manganate Nd_0.5Ca_0.5MnO_3

Measurements of the dc transport properties and the low-frequency conductivity noise in films of charge ordered Nd_0.5Ca_0.5MnO_3 grown on Si subtrate reveal the existence of a threshold field in the charge ordered regime beyond which strong non linear conduction sets in along with a large broad band conductivity noise. Threshold-dependent conduction disappears as T -> T_{CO}, the charge ordering temperature. This observation suggests that the charge ordered state gets depinned at the onset of the non-linear conduction.Comment: 3 pages of two-column text and 4 eps figure