High-energy Quanta Research Articles

Quantum information scrambling and quantum chaos in little string theory

In the current manuscript we perform a systematic investigation about the effects of nonlocal interaction to the spread of quantum information in many body system. In particular, we have studied how nonlocality influence the existing bound on the growth rate of the commutator involving two local operators, the butterfly velocity. For this purpose, we consider the nonlocal theory on the worldvolume of N ≫ 1, NS5 branes arising in the limit of vanishing string coupling, the ‘little string theory’. A direct evidence of nonlocality can be realized from the ‘volume law’ behavior for the most dominant part of holographic entanglement entropy. We obtain the butterfly velocity by studying the dynamics of the near horizon geometry backreacted by a high energy quanta in the form of a shockwave resulting from an early perturbation on the corresponding thermofield double state. We observe that the butterfly velocity increases with the nonlocal scale of little string theory, the inverse Hagedorn temperature βh, indicating a faster rate of information spread due to the nonlocal interaction. The same conclusion follows as the disruption of two sided mutual information is observed to occur at a faster rate for higher values of βh. Finally, we realize a direct connection between the parameters of quantum chaos and the quasinormal modes for collective excitations through the phenomenon of ‘pole skipping’.

Nanoscale optical writing through upconversion resonance energy transfer.

Nanoscale optical writing using far-field super-resolution methods provides an unprecedented approach for high-capacity data storage. However, current nanoscale optical writing methods typically rely on photoinitiation and photoinhibition with high beam intensity, high energy consumption, and short device life span. We demonstrate a simple and broadly applicable method based on resonance energy transfer from lanthanide-doped upconversion nanoparticles to graphene oxide for nanoscale optical writing. The transfer of high-energy quanta from upconversion nanoparticles induces a localized chemical reduction in graphene oxide flakes for optical writing, with a lateral feature size of ~50 nm (1/20th of the wavelength) under an inhibition intensity of 11.25 MW cm-2 Upconversion resonance energy transfer may enable next-generation optical data storage with high capacity and low energy consumption, while offering a powerful tool for energy-efficient nanofabrication of flexible electronic devices.

Photonuclear Technology for Hidden Explosive Detection

The photonuclear technology for explosive detection is based on the recording of the decays of short-lived 12B and 12N isotopes. These radionuclides are formed in reactions on 14N and 13C nuclei under effect of irradiation by high-energy gamma quanta. Carbon and nitrogen are found in the composition of all explosives. We can obtain the information for the identification of the explosives based on the time spectra of the signals of isotope decays after the pulsed irradiation of the object. The operational parameters of the detectors for baggage screening and humanitarian demining were obtained by computer simulation. We developed a laboratory unit consisting of a 55-MeV racetrack microtron, 250-L Cherenkov water counter, and VME standard electronics to study the technology. The experimental results obtained using this equipment are discussed.

Simulation of the Focal Spot of the Accelerator Bremsstrahlung Radiation

Testing of thick-walled objects by bremsstrahlung radiation (BR) is primarily performed via high-energy quanta. The testing parameters are specified by the focal spot size of the high-energy bremsstrahlung radiation. In determining the focal spot size, the high- energy BR portion cannot be experimentally separated from the low-energy BR to use high- energy quanta only. The patterns of BR focal spot formation have been investigated via statistical modeling of the radiation transfer in the target material. The distributions of BR quanta emitted by the target for different energies and emission angles under normal distribution of the accelerated electrons bombarding the target have been obtained, and the ratio of the distribution parameters has been determined.

More About Radioactive Pollution

Radiation is the emission of particle or energy in wave form. This is stated as electromagnetic radiation. Examples consist of: visible light, radio waves, microwaves, infrared and ultraviolet lights, X-rays, and gamma-rays (1). Radiation can be described as two basic types, ionizing and non-ionizing radiation. The discussion will include a review of radiation of radioactivity. There are three main kinds of ionizing radiation which are included alpha particles, beta particles and gamma rays. Beside these there forms of ionizing also we have neutrons, protons, heavy charged particles, X-ray and others. Radioactive substance can penetrate into the body by inhalation, ingestion or dermal absorption. In addition, gamma radiation external to the body can enter the skin and produce a dose various tissues (2). Non ionizing radiation refers to radioactive energy which as opposed to produce charged ions when passing through matters has enough energy only for excitation. However it is known to cause biological effects. Non ionizing radiations usually work together with tissue through the generation of heat. The hazard depends on the ability to go through the human body and the absorption characteristics of different tissues (3). If each and every one of these types of radiation added by human activities can cause radiation pollution. The meaning of radiation pollution is that while there are omnipresent sources of radiation, generally the highenergy radiations cause radiation pollution with a serious health risk (such as cancer or death) (4). As has been mentioned air pollution can caused by radioactivity which are in the air as gas or aerosols that emit such ionizing radiation as alpha and beta particles, gamma rays, neutrons and other high energy quanta. From the beginning of the life story the man has been exposed to ionizing radiations from radioactive isotopes and other sources by development of atomic reactor. This kind of pollution has been raised considerably (5, 6). Exposure radiation can cause tissue and organ injury unless suitable precautions are taken. The more important health effects described as being caused by radioactive isotopes are blood abnormalities, skin changes, bone

The phenomenon of scintillation in solids

The scintillation materials are widely used in science and industry, however, till now there is no complete definition of the phenomenon as a whole. The conversion of energy loss of particles and γ-quanta into light by luminescent medium is the general definition of scintillation. In our report we analyze possibilities when scintillation arise not only when charged particles and high-energy quanta pass through the scintillating material, but also when particles move near its surface. Several definitions of the scintillation phenomenon are debated.

Digital position sensitive discrimination for 2-dimensional scintillation detectors

The energy sensitivity of a two-dimensional scintillation gamma detector based on position sensitive photomultipliers has been minimized by a digital differential discrimination unit. Since the photomultiplier gain is position-dependent by /spl plusmn/50%, a discrimination unit has been developed of which the digital upper and lower discrimination levels are set to the position-dependent photomultiplier gain obtained from calibration measurements. Depending on the spatial resolution, there can be up to 65,536 position-sensitive discriminator levels defining energy windows. By this method, narrow discriminator windows can be used for reducing the low and high energy quanta without effecting the sensitivity of the detector. The new discrimination method, its performance and test measurements with gamma rays are described. Further experimental results are also presented.

ELECTRON–HOLE BRANCH IMBALANCE IN SUPERCONDUCTORS INITIATED BY ABSORPTION OF HIGH-ENERGY QUANTA

The creation of quasiparticle branch imbalance in superconductors, when pumped by high-energy quanta, is considered. The physical basis for imbalance creation lies in the geometrical difference between the electron- and hole-like excitation densities of states in momentum space. Simple analytical solutions for distribution functions of electron- and hole-like excitations are derived using appropriately modified kinetic equations. The relevance of results to the problem of high-energy particle detection is discussed.

Quantum-radiation spectra of relativistic particles derived by the correspondence principle.

It is known that ultrarelativistic electrons, when moving nearly parallel to an axis in a single crystal, will emit very intense radiation containing high-energy quanta. The radiation spectra are connected to synchrotron spectra in excessively strong magnetic fields. The latter spectra have previously been calculated by quantum perturbation theory, and are much reduced compared to the corresponding classical spectra. By application of the correspondence principle, it is shown that, for spin-zero particles, the complete quantum spectrum is obtained exactly from the classical spectrum by a simple modification of the frequency variable. The result holds for arbitrary external fields and with respect to angular distribution, polarization, and frequency distribution. Agreement with previous calculations of the synchrotron case is verified. For spin-1/2 particles the quantum frequency spectrum can be expressed with satisfactory accuracy by the classical radiation of spin-zero particles. These results may be of assistance in our understanding of radiation by ultrarelativistic particles.

High-energy phenomena on the Sun: An introductory review

Large solar flares are often accompanied by both emissions of high-energy quanta and particles. The emissions such as gamma-ray and hard X-ray photons are generated due to the interaction of high-energy nuclei and electrons with gases ambient in the flare regions and the solar atmosphere. Nonthermal radio emissions of wide frequency band are produced from energetic electrons while being decelerated by the action of plasmas and magnetic fields ambient in the flare site and its neighboring region. To understand the emission mechanism of these high-energy quanta on the Sun, it is, therefore, necessary to find the acceleration mechanism for both nuclei and electrons, which begins almost simultaneously with the onset of solar flares. A part of the accelerated nuclei and electrons are later released from the solar atmosphere into the outer space and eventually lost from the space of the solar system. Their behavior in the interplanetary space is considered to study the large-scale structure of plasmas and magnetic fields in this space. The observations and studies of high-energy phenomena on the Sun are thus thought of as giving some crucial hint important to understand the nature of various high-energy phenomena being currently observed in the Universe.

On the role of electron correlation in the photoionisation of atoms by high-energy quanta

The photoionisation of multi-electron atoms with non-zero angular momenta is discussed in terms of the electric dipole approximation for non-relativistic photoelectrons. It is shown that at high photoelectron energy, k2>>1, the main asymptotic term of the cross section corresponds to an outgoing p wave independent of the initial electron angular momentum, while the momenta of the initial atom and residual ion are the same. The photoionisation amplitude, excluding parity-forbidden cases, depends on k in the same way as the amplitude for photoionisation of 1s hydrogen, AH. The selection rules obtained show that the line in the photoelectron spectrum due to the two-electron transition may be of even higher intensity than the one-electron line.

Comparison of the kumakhov radiation in channeling with other types of radiation

Abstract A detailed comparison is made of the Kumakhov radiation with the coherent bremsstrahlung, the transition radiation and the synchroton radiation. The coherent bremsstrahlung was shown to be suppressed under channeling conditions. It was found that the mechanism of the appearance of the Kumakhov radiation differs greatly from that for the coherent bremsstrahlung and the transition radiation. The Kumakhov radiation was shown to be more intensive than the synchrotron radiation, especially in the region of high-energy quanta.

Adaptation to Equivalent Visible and High-Energy Quanta

By adjusting to equivalence the stimulating effectiveness of light and x-rays, the processes of adaptation were measured by rate of optic nerve unit discharge. Light adaptation is a simple exponential function. Adaptation to x-irradiation is a complex function composed of an early exponential decay in response rate and a late exponential rise in response rate. The response to light returned to normal 3 minutes after x-ray adaptation was terminated. The hypothesis that light and x-rays have identical effects on rhodopsin-bearing visual systems was not supported.

Radiation Chemistry of Carbohydrates

This chapter discusses the basic principles of the radiation chemistry of carbohydrates. Biological action of radiations, chemical utilization of fission-product radiations, and the use of radiation in the sterilization of food stimulated an intensive study into the effects of ionizing radiations on organic compounds. The radiation chemistry embraces photochemistry––the chemistry of reactions that occur in electrical discharges and reactions in the atomic nucleus by the agency of neutrons and high-energy radiations. The chapter describes the chemical changes induced by the radiation that may be electromagnetic (x-rays and γ-rays) or corpuscular (α-rays and β-rays), and the final transfer of energy occurs by way of charged particles. With electromagnetic radiation, interaction of high-energy quanta with atoms of the medium through which they pass leads to ionization, because the energy of the quanta is substantially greater than the binding energy of an electron.

Spectral Sensitivity of Two Commercial X-Ray Films between 0.2 and 2.5 Angstroms

The spectral sensitivities of Kodak No-Screen and Kodak Industrial Type K X-Ray Films were determined in the region between 0.2 and 2.5A using the filtered K fluorescence of several irradiated elements as approximately homogeneous radiation. Exposures in roentgens were obtained with an air ionization chamber designed especially for the purpose. Curves are given showing the number of roentgens incident on the film which will give a developed photographic density of 1.0 above fog for the various wave-lengths. The K limits of silver and bromine are prominent. The maximum sensitivity in terms of roentgens occurs at about 0.4A, but the marked decrease found by other observers at shorter wave-lengths is probably obscured by inaccuracies. From the energy value of the roentgen, the sensitivity of the films is expressed as the incident ergs per square centimeter required to produce a density of 1.0 above fog. Computations from these results show that as the wave-length increases the films utilize the absorbed energy more efficiently. On the other hand, high energy quanta are more efficient than low energy quanta but not in proportion to their energy. In addition to the more or less gradual change with wave-length of efficiency of utilization of absorbed energy, there is evidence for sudden jumps at the K limits of Ag and Br. Qualitative explanations are given for the observed changes in efficiency.

The luminescence of photo-conducting phosphors.

Studies have been made of the effects of non-radiative loss of the energy absorbed by phosphors which occur when excitation frees electrons from luminescence centers in the phosphors so that they move freely in the matrix crystal. Such non-radiative losses also occur at elevated temperatures when the thermal energy of the phosphor is sufficient to free electrons from the excited states of the emission centers. These processes give rise to a non-linear variation of the luminescence intensity with the intensity of excitation, as observed by previous workers. In addition to more exhaustive studies of this non-linear behavior of the luminescence, we have made studies of the semi-conduction, photo-conduction and thermoelectric effects in phosphors at temperatures where the non-radiative processes are present. These electrical measurements show that at elevated temperatures phosphors behave as excess semi-conductors, that is, the observed current is due mainly to electrons and not to positive hole motion, as assumed by some previous workers. The investigations provide a qualitative explanation of the low efficiency of excitation of phosphors by particles or high energy quanta. They show that for excitation by ultraviolet light of wave-length greater than that of the fundamental absorption edge of the phosphor matrix (zinc sulphide phosphors), the electrons excited do not leave the neighborhood of the emission centers and only give rise to transient photoconductivity effects having the nature of displacement currents.

Societies and Academies

Edinburgh Royal Society of Edinburgh, December 6. H. J. BHABHA: Production of electron showers by cosmic rays. Blackett and Occhialini showed in 1932 that cosmic rays produce showers. The quantum theory is capable of explaining these showers. Very high energy electrons lose practically their whole energy by emitting a few high energy quanta. Each high energy quantum is chiefly absorbed by the creation of a pair of positive and negative electrons. When, therefore, a very high energy electron passes through matter, it emits a few hard quanta, each of which in turn produces an electron pair, which again emit quanta and so on. Thus, if the initial energy be high enough, many hundred particles may be created, forming a shower.

The scattering of hard gamma rays.—Part II

Three papers have recently appeared describing investigations of the absorption of the very hard γ-rays from thorium C˝ in a number of elements, and in each case the conclusion was drawn that the results indicate that these very high energy quanta are capable of interacting with certain atomic nuclei. The three sets of experimental results do not agree in detail, but in each case the trend of the variation of absorption coefficient with atomic number is very different form the Z 3 law characteristic of photoelectric absorption. Moreover, the difference between the absorption coefficients per electron in heavy and light elements, which has hitherto been attributed to photoelectric absorption, is nearly as great for the hard thorium C˝ γ-rays ( hv =2·65. 10 6 ε-volts), as for the much softer redium C γ-rays ( hv ~ 1·8. 10 6 ε-volts), in marked contrast with the rapid variation with wave-length observed in the softer γ-ray region of the spectrum. Very little is at present know concerning the magnitude of the photo-eletric effect in the γ-rays region, and since absorption coefficients measured in the usual manner are the sum of two terms referring respectively to scattering and to photoelectric absorption, it is essential for the further elucidation of the problem to study the actual scattered radiation.