Ultra-high-energy cosmic rays and inflation relics

There are two processes of matter creation after inflation that may be relevant to the resolution of the puzzle of cosmic rays observed with energies beyond GZK cut-off: 1) gravitational creation of superheavy (quasi)stable particles, and 2) non-thermal phase transitions leading to the formation of topological defects. We review both possibilities.     

Trans-Planckian particle creation in cosmology and ultrahigh energy cosmic rays

We consider observational constraints on the creation of particles induced by hypothetical trans-Planckian effects during the current stage of the Universe’s expansion. We show that compatibility with the diffuse γ-ray background measured by the EGRET experiment strongly restricts this creation. In particular, it rules out the possibility of detecting signatures of such short-distance effects in anisotropies of the cosmic microwave background radiation. On the other hand, the possibility that some part of ultrahigh-energy cosmic rays originates from new trans-Planckian physics remains open.     

Quantum theory of transition radiation and transition pair creation

A theory of the transition radiation and the transition pair creation is developed in the frame of QED. The spectral-angular distributions of probability of the transition radiation and of the transition pair creation are found. The total energy losses of an electron and the total probability of pair creation by a photon are calculated and analyzed. Features of radiation and pair creation processes in a superdense medium (typical for white dwarfs) are discussed.     

Cosmic ray-aerosol-cloud interactions in the atmospheric environment: Theoretical aspects

The microphysical and radiative processes involved in the interaction of cosmic radiation with the aerosol particulates in the atmosphere aggravate the ion-induced formation of aerosol particles that can act as cloud condensation nuclei (CCN). This may in turn affect the cloud droplet distribution and optical properties of clouds and enhance the process of rising global temperature depending upon the microphysical mechanism. Major observational information about the abundance of aerosols in the tropical atmosphere are obtained from the Indian Ocean experiment (INDOEX) field experiments and about the solar activity and solar cycle from the satellite observations. It has been noticed that when solar activity is less, more cosmic rays pass through the atmosphere, which activate the aerosols already present in the tropical atmosphere. The fluctuations in the cosmic rays due to variations in the solar activity can produce significant changes in the atmospheric environment.     

Exciton-polaritons by two-photon absorption in semiconductors

The creation of excitonic polariton states by two-photon absorption is theoretically investigated. A semi-classical approach is adopted to compute the two-photon transition probability to polariton states through an intermediate exciton state. The numerical results in CuCl show two peaks corresponding to the longitudinal exciton and transverse polariton states, respectively. These results are in good agreement with the experiment.     

Search for anomalous and exotic cosmic rays phenomena in the CMS experiment on the CASTOR calorimeter at the large hadron collider

The creation of the CASTOR forward calorimeter in the compact muon spectrometer (CMS) experiment at the Large Hadron Collider (LHC), CERN enabled us to perform experiments at energies corresponding to those of cosmic rays but at much greater intensities, the most important factor in studying rare and anomalous phenomena.     

Implications of cosmic string-induced density fluctuations at the quark-hadron transition

We show that cosmic strings moving through the plasma at the time of a first-order quark-hadron transition in the early universe generate baryon inhomogeneities, which can survive till the nucleosynthesis epoch. We find out how these inhomogeneities actually affect the calculated values of the light element abundances. Recently a wealth of observational data from various experiments have helped to reduce the uncertainties in the values of these abundances. Using these we show that it is possible to derive constraints in the presence of cosmic strings during the quark-hadron transition.     

Brane factories

We propose that higher-dimensional extended objects (p-branes) are created by super-Planckian scattering processes in theories with TeV scale gravity. As an example, we compute the cross section for p-brane creation in a (n+4)-dimensional spacetime with asymmetric compactification. We find that the cross section for the formation of a brane which is wounded on a compact submanifold of size of the fundamental gravitational scale is larger than the cross section for the creation of a spherically symmetric black hole. Therefore, we predict that branes are more likely to be created than black holes in super-Planckian scattering processes in these manifolds. The higher rate of p-brane production has important phenomenological consequences, as it significantly enhances possible detection of non-perturbative gravitational events in future hadron colliders and cosmic rays detectors.     

Kinetic description of vacuum creation of massive vector bosons

In the simple model of massive vector field in a flat spacetime, we derive the kinetic equation of non-Markovian type describing the vacuum pair creation under action of external fields of different nature. We use for this aim the nonperturbative methods of kinetic theory in combination with a new element when the transition of the instantaneous quasiparticle representation is realized within the oscillator (holomorphic) representation. We study in detail the process of vacuum creation of vector bosons generated by a time-dependent boson mass in accordance with the framework of a conformal-invariant scalar-tensor gravitational theory and its cosmological application. It is indicated that the choice of the equation of state allows one to obtain a number density of vector bosons that is sufficient to explain the observed number density of photons in the cosmic microwave background radiation.     

Vortex quantum creation and winding number scaling in a quenched spinor Bose gas

Motivated by a recent experiment, we study nonequilibrium quantum phenomena taking place in the quench of a spinor Bose-Einstein condensate through the zero-temperature phase transition separating the polar paramagnetic and planar ferromagnetic phases. We derive the typical spin domain structure (correlations of the effective magnetization) created by the quench arising due to spin-mode quantum fluctuations, and we establish a sample-size scaling law for the creation of spin vortices, which are topological defects in the transverse magnetization.     

Stimulated creation of quanta during inflation and the observable universe

Inflation provides a natural mechanism to account for the origin of cosmic structures. The generation of primordial inhomogeneities during inflation can be understood via the spontaneous creation of quanta from the vacuum. We show that when the corresponding stimulated creation of quanta is considered, the characteristics of the state of the universe at the onset of inflation are not diluted by the inflationary expansion and can be imprinted in the spectrum of primordial inhomogeneities. The non-gaussianities (particularly in the so-called squeezed configuration) in the cosmic microwave background and galaxy distribution can then tell us about the state of the universe that existed at the time when quantum field theory in curved spacetime first emerged as a plausible effective theory.     

Quantum quenches in a spinor condensate

We discuss the ordering of a spin-1 condensate when quenched from its paramagnetic phase to its ferromagnetic phase by reducing the magnetic field. We first elucidate the nature of the equilibrium quantum phase transition. Quenching rapidly through this transition reveals XY ordering either at a specific wave vector, or the "light-cone" correlations familiar from relativistic theories, depending on the end point of the quench. For a quench proceeding at a finite rate the ordering scale is governed by the Kibble-Zurek mechanism. The creation of vortices through growth of the magnetization fluctuations is also discussed. The long-time dynamics again depends on the end point, conserving the order parameter in a zero field, but not at a finite field, with differing exponents for the coarsening of magnetic order. The results are discussed in the light of a recent experiment by Sadler et al.     

Observation of magnetic flux generated spontaneously during a rapid quench of superconducting films

We report observations of spontaneous formation of magnetic flux lines during a rapid quench of YBa(2)Cu(3)O(7-delta) films through T(c). This effect is predicted according to the Kibble-Zurek mechanism of creation of topological defects of the order parameter during a symmetry-breaking phase transition. Our previous experiment, at a quench rate of 20 K/s, gave null results. In the present experiment, the quench rate was increased to >10(8) K/s. The amount of spontaneous flux increases weakly with the cooling rate.     

First order QED processes in a spatially flat FLRW space-time with a Milne-type scale factor

The quantum electrodynamics(QED)in a spatially flat(1+3)-dimensional Friedmann-Lema?tre-Robertson-Walker(FLRW)space-time with a Milne-type scale factor is outlined focusing on the amplitudes of the allowed processes in the first order perturbations.The definition of the transition rates is reconsidered such that an appropriate angular behavior of the probability for creation of an electron-positron pair from a photon is obtained,which has a similar rate as the creation of a photon and an electron-positron pair from vacuum.It is shown that these processes are allowed only in the first order perturbations,since the photon emission or absorption by an electron or positron are forbidden.     

Measuring the small-scale power spectrum of cosmic density fluctuations through 21 cm tomography prior to the epoch of structure formation

The thermal evolution of the cosmic gas decoupled from that of the cosmic microwave background (CMB) at a redshift z approximately 200. Afterwards and before the first stars had formed, the cosmic neutral hydrogen absorbed the CMB flux at its resonant 21 cm spin-flip transition. We calculate the evolution of the spin temperature for this transition and the resulting anisotropies that are imprinted on the CMB sky due to linear density fluctuations during this epoch. These anisotropies, at an observed wavelength of 10.56[(1+z)/50] m, contain an amount of information that is orders of magnitude larger than any other cosmological probe.     

Cosmic rays in the Earth’s atmosphere

This paper presents a brief historical overview of studies of cosmic rays in the Earth’s atmosphere, which were initiated and led by S.N. Vernov for over 50 years. The main results of these studies that were obtained in recent decades are given. They include the study of the processes of generation and propagation of solar cosmic rays, the modulation of galactic cosmic rays in the heliomagnetosphere, and the role of cosmic rays in atmospheric processes.     

A natural way out of the conflict between cosmic strings and inflation

The phase transition which produces cosmic strings is studied in curved spacetime. It is shown that cosmic string formation naturally takes place in the late inflationary stage if the string-forming scalar field is appropriately coupled with the spacetime curvature. As a result the cosmic string scenario of galaxy formation turns out to be compatible with inflation.     

Characteristics of Forbush Decreases Measured by the PAMELA Instrument During 2006–2014

During the several decades of Forbush decrease (FD) studies the main properties of this phenomenon were established. Today is clear that Forbush decreases originate as the responses of cosmic ray particle fluxes to solar-induced processes inside interplanetary space. Moreover the profiles of FD’s are the manifestation of the complex structure of coronal mass ejections (CMEs) which are driving from the Sun and often accompanied by flares. So the investigation of FD’s is a useful tool for understanding the dynamics of CME processes and the effects they have on in the interplanetary space. Classification and theoretical interpretation of different FD’s are important for understanding the complex effect of CME’s as well as the search for new features of their behavior. Spectra of cosmic ray protons and helium nuclei obtained by the PAMELA experiment in the rigidity range between 1–15 GV were used to investigate the characteristics of Forbush decreases. Additional data on the interplanetary magnetic field and solar wind speed were taken from the ACE data center for correlation analysis. Rigidity dependences for selected Forbush decreases are also presented.

     

Artem Isaak Alikhanian (1908–1978) (Biographic Sketch)

A.I. Alikhanian is one of founders of experimental nuclear physics in USSR. Starting and development of the atomic nuclei, cosmic ray, and elementary particle physics in Armenia relates to the name Alikhanian. He created the Aragats and Nor-Amberd high-altitude cosmic stations and the Yerevan Physics Institute. He made an essential contribution into the development of high-energy physics and played a significant role in creation of methods of recording high-energy particles.     

Abundance of actinides in cosmic radiation

Ultra heavy (UH) cosmic rays of Z65 are produced either by s- or r-process of nucleosynthesis. Since these two processes occur under different astrophysical environments, the relative abundances of UH ions could be an important parameter in finding their source and origin. Data analysis is carried out on four detector stacks exposed in space by UH cosmic ray experiment on board LDEF. Scanning and analysis of 0.21 m² detector area resulted in finding of 72 UH ions (68Z96) including two actinides (88Z100). The ratio of actinides to that of sub-actinides is found to be 0.034±0.024, which is well within the observational limits of other experiments. Results suggest possible sources, which predominantly ejects r-process synthesized material.