Axion emission from a hot plasma

We give the technics for the calculation of production and energy loss rates for axion-like particles (scalar or pseudo-scalar coupling to the gauge boson) from a hot QED (or QCD) heat bath. We compute the contribution coming from, the decay mode of a transverse to a longitudinal photon (or gluon). The energy loss rate for this process behaves asT ⁷. Considering the supernova SN1987A event, this behaviour could improve the upper bound on the coupling constant between asions and photons.     

Chiral phase transition from string theory

The low energy dynamics of a certain D-brane configuration in string theory is described at weak t'Hooft coupling by a nonlocal version of the Nambu-Jona-Lasinio model. We study this system at finite temperature and strong t'Hooft coupling, using the string theory dual. We show that for sufficiently low temperatures chiral symmetry is broken, while for temperatures larger then the critical value, it gets restored. We compute the latent heat and observe that the phase transition is of the first order.     

Real Time Imaging of Quantum and Thermal Fluctuations: The Case of a Two-Level System

A quantum system in contact with a heat bath undergoes quantum transitions between energy levels upon absorption or emission of energy quanta by the bath. These transitions remain virtual unless the energy of the system is measured repeatedly, even continuously in time. Isolating the two indispensable mechanisms in competition, we describe in a synthetic way the main physical features of thermally activated quantum jumps. Using classical tools of stochastic analysis, we compute in the case of a two-level system the complete statistics of jumps and transition times in the limit when the typical measurement time is small compared to the thermal relaxation time. The emerging picture is that quantum trajectories are similar to those of a classical particle in a noisy environment, subject to transitions à la Kramer in a multi-well landscape, but with a large multiplicative noise.     

Nanoscale electrostatic manipulation of magnetic flux quanta in ferroelectric/superconductor BiFeO3/YBa2Cu3O(7-δ) heterostructures

Using heterostructures that combine a large-polarization ferroelectric (BiFeO3) and a high-temperature superconductor (YBa2Cu3O(7-δ)), we demonstrate the modulation of the superconducting condensate at the nanoscale via ferroelectric field effects. Through this mechanism, a nanoscale pattern of normal regions that mimics the ferroelectric domain structure can be created in the superconductor. This yields an energy landscape for magnetic flux quanta and, in turn, couples the local ferroelectric polarization to the local magnetic induction. We show that this form of magnetoelectric coupling, together with the possibility to reversibly design the ferroelectric domain structure, allows the electrostatic manipulation of magnetic flux quanta.     

Black hole as a point radiator and recoil effect on the brane world

A small black hole attached to a brane in a higher-dimensional space emitting quanta into the bulk may leave the brane as a result of a recoil. We construct a field theory model in which such a black hole is described as a massive scalar particle with internal degrees of freedom. In this model, the probability of transition between the different internal levels is identical to the probability of thermal emission calculated for the Schwarzschild black hole. The discussed recoil effect implies that the thermal emission of the black holes, which might be created by interaction of high energy particles in colliders, could be terminated and the energy nonconservation can be observed in the brane experiments.     

Multiphoton stimulated bremsstrahlung for broad (in the momentum representation) electron wave packets in an ultrashort laser pulse field

We consider features of absorption and emission of external laser field quanta by a broad (in the momentum representation) electron wave packet during its scattering from a potential center. Various scattering modes for the electron wave packet in a high-intensity laser field are analyzed using perturbation theory of potential energy. It is found that the absorption of laser field energy by an electron is substantially more effective as compared to the case of a plane wave. The important role of a number of interference effects associated with the large width of the initial electron momentum distribution is demonstrated.     

Time Quanta

Secondary quantizing of the “passive mass” of an isotropic and uniform nonstationary scalar field is realized, and the intensity of quantum emission of the massless scalar field is calculated for spontaneous transitions of the effective Planck particle in the line energy spectrum of the primordial Lema?tre atom. It is shown that the scalar-field quanta in the effective Riemann space can manifest themselves as time quanta of the real Minkowski space.     

Modulation of charge transfer rate in (N,N′-dimethylamino)benzonitrile liquid solutions

We studied the properties of the emission, absorption and excitation of dual fluorescence of (N,N′?dimethylamino)benzonitrile in a polar aprotic solvent acetonitrile under selective irradiation of solutions by light with different energies of quanta to elucidate mechanisms of dual fluorescence arising in this solvent at different temperatures in the range 274–313 K. In all cases, dual fluorescence of the solute in acetonitrile was observed, which is caused by emission from locally excited Franck-Condon and charge-transfer states. A change in the energy of excitation quanta has a weak effect on the position of the fluorescence bands; however, the intensity ratio between the bands noticeably changes in favour of the intensity of the long-wavelength band at excitation in the range of the long-wavelength absorption band. An interesting and unusual fact is that solution heating is accompanied by essential growth of quantum yield of dual fluorescence at all wavelengths of the excitation. To explain the observed effects, the same dependences were measured and analysed for DMABN in neutral solvent n-hexane in the same conditions. We involve also the data of quantum-mechanical calculations, which show that there is a considerable probability of occurrence in solutions of DMABN rotational isomers with differing orientation of the dimethylamino group with respect to the benzonitrile. In the excited state, these have different charge-transfer rates, resulting in a modulation in the intensity ratio of the observed fluorescence bands with change excitation energy quanta on the red wing of the absorption band, doi: 10.1134/S0030400X12050219.     

Theoretical studies on the photophysical properties of some Iridium (III) complexes used for OLED

The structural and photophysical properties of four heteroleptic Iridium (III) complexes, based on 1-phenylpyrazole ligand, have been investigated theoretically. The effect of chemical substitution on the absorption and the emission spectra of the complexes has been studied and compared with the experimental data. We observe a significant structural change in the lowest triplet excited state as compared to the ground singlet state. We compute the emission wavelength of the complexes by considering the spin-orbit coupling. Using these understandings, we predict two new complexes having deeper blue emission which are supposed to be better efficient OLED materials.     

Reheating,thermalization and non-thermal gravitino production in MSSM inflation

In the framework of MSSM inflation, matter and gravitino production are here investigated through the decay of the fields which are coupled to the udd inflaton, a gauge-invariant combination of squarks. After the end of inflation, the flat direction oscillates about the minimum of its potential, losing at each oscillation about 56% of its energy into bursts of gauge/gaugino and scalar quanta when crossing the origin. These particles then acquire a large inflaton VEV-induced mass and decay perturbatively into the MSSM quanta and gravitinos, transferring the inflaton energy very efficiently via instant preheating. Regarding thermalization, we show that the MSSM degrees of freedom thermalize very quickly, yet not immediately by virtue of the large vacuum expectation value of the inflaton, which breaks the \(SU(3)_C\times U(1)_Y\) symmetry into a residual U(1). The energy transfer to the MSSM quanta is very efficient, since full thermalization is achieved after only \(\mathcal {O}(40)\) complete oscillations. The udd inflaton thus provides an extremely efficient reheating of the Universe, with a temperature \(T_{\text {reh}}=\mathcal {O}(10^8\,{\text {GeV}})\), which allows for instance several mechanisms of baryogenesis. We also compute the gravitino number density from the perturbative decay of the flat direction and of the SUSY multiplet. We find that the gravitinos are produced in negligible amount and satisfy cosmological bounds such as the Big Bang nucleosynthesis (BBN) and dark matter (DM) constraints.     

Beam energy dependence of spontaneous positron creation in delayed nuclear collisions

We compute positron emission from U+Cm collisions within a quantum mechanical model for delayed nuclear collisions. We demonstrate a striking beam energy dependence of the strength of the spontaneous positron peak.     

Comparison of two models for phonon assisted tunneling field enhanced emission from defects in Ge measured by DLTS

Deep Level Transient Spectroscopy (DLTS) was used to measure the field enhanced emission rate from a defect introduced in n-type Ge. The defect was introduced through low energy (±80 eV) inductively coupled plasma (ICP) etching using Ar. The defect, named EP_0.31, had an energy level 0.31 eV below the conduction band. Models of Pons and Makram-Ebeid (1979) [2] and Ganichev and Prettl (1997) [3], which describe emission due to phonon assisted tunneling, were fitted to the observed electric field dependence of the emission rate. The model of Pons and Makram-Ebeid fitted the measured emission rate more accurately than Ganichev and Prettl. However the model of Ganichev and Prettl has only two parameters, while the model of Pons and Makram-Ebeid has four. Both models showed a transition in the dominant emission mechanism from a weak electron–phonon coupling below 152.5 K to a strong electron–phonon coupling above 155 K. After the application of a χ² goodness of fit test, it was determined that the model of Pons and Makram-Ebeid describes the data well, while that of Ganichev and Prettl does not.     

Hadronic spectrum of a holographic dual of QCD

We compute the spectrum of light hadrons in a holographic dual of QCD defined on AdS5 x S5 which has conformal behavior at short distances and confinement at large interquark separation. Specific hadrons are identified by the correspondence of string modes with the dimension of the interpolating operator of the hadron's valence Fock state. Higher orbital excitations are matched quanta to quanta with fluctuations about the AdS background. Since only one parameter, the QCD scale Lambda(QCD), is used, the agreement with the pattern of physical states is remarkable. In particular, the ratio of delta to nucleon trajectories is determined by the ratio of zeros of Bessel functions.     

Quantum photon emission from a moving mirror in the nonperturbative regime

We consider the coupling of the electromagnetic vacuum field with an oscillating perfectly-reflecting mirror in the nonrelativistic approximation. As a consequence of the frequency modulation associated to the motion of the mirror, low frequency photons are generated. We calculate the photon emission rate by following a nonperturbative approach, in which the coupling between the field sidebands is taken into account. We show that the usual perturbation theory fails to account correctly for the contribution of TM-polarized vacuum fluctuations that propagate along directions nearly parallel to the plane surface of the mirror. As a result of the modification of the field eigenfunctions, the resonance frequency for photon emission is shifted from its unperturbed value.     

Effects of long-wavelength fluorescence excitation in N, N′-dimethylaminobenzonitrile liquid solutions

We have studied the properties of the emission, absorption, and excitation of dual fluorescence of N,N??-dimethylaminobenzonitrile in a set of solvents of different polarity under selective irradiation of solutions by light with different energies of quanta in the range of the long-wavelength absorption band. In all cases, dual fluorescence is observed, which is caused by emission from locally excited Franck-Condon and charge-transfer states. A change in the energy of excitation quanta has no effect on the position of the fluorescence bands; however, the intensity ratio between the bands noticeably changes in favor of the intensity of the long-wavelength band, which belongs to the charge-transfer state. To explain the observed effects, we involve data of quantum-mechanical calculations, which show that there is a considerable probability of occurrence in solutions of these systems of rotational isomers that differ in the orientation of the dimethylamino group with respect to benzonitrile. In the excited state, these rotamers have different charge-transfer reaction rates, which leads to a change in the intensity ratio of the observed fluorescence bands upon using the selective excitation.     

Effect of Silane Pressure on Silane-Hydrogen RF Glow Discharges

The intensity and time dependence of optical emission from silane and silane-hydrogen radio-frequency (RF) discharges have been measured as a function of silane pressure (0.05-1.0 torr). The rate of emission of H* and Si* resulting from dissociative excitation was found to decrease with increasing silane pressure in a manner consistent with a similar decrease in average electron energy. Results from a Monte Carlo plasma simulation code were used to compute the rate of optical emission. Comparison of theory and experiment shows good agreement for emission intensities and confirms for discharges operating at constant pressure and power density a decrease in electron density and average electron energy with increasing silane partial pressure in mixtures of silane and hydrogen. The time-dependent spatially averaged emission intensity of H* is experimentally nonsymmetric with a shape that is a systematic function of silane partial pressure. This systematic behavior is reproduced by the plasma simulation and is attributed to the change in the dc bias of the powered electrode, which becomes less negative with increasing silane partial pressure.     

Mechanism of blackbody radiation

The law of error for Bose statistics is not unique; the family of probability distributions differ insofar as zero-point energy is concerned. This is traced back to the spontaneous emission term in the Einstein mechanism of emission and absorption of radiation. It is argued that the spontaneous emission term is unimportant for blackbody radiation and an alternative mechanism is proposed in which thermal equilibrium is secured through a constraint on the number of quanta in any given mode of the radiation field. Both mechanisms predict a modification of the Maxwell velocity distribution at high frequencies and are compared in relation to Doppler broadening and their low-temperature behavior.     

Surface plasmon amplification by stimulated emission of radiation: quantum generation of coherent surface plasmons in nanosystems

We make a step towards quantum nanoplasmonics: surface plasmon fields of a nanosystem are quantized and their stimulated emission is considered. We introduce a quantum generator for surface plasmon quanta and consider the phenomenon of surface plasmon amplification by stimulated emission of radiation (spaser). Spaser generates temporally coherent high-intensity fields of selected surface plasmon modes that can be strongly localized on the nanoscale, including dark modes that do not couple to far-zone electromagnetic fields. Applications and related phenomena are discussed.     

Controlling energy coupling and particle ejection from aluminum surfaces irradiated with ultrashort laser pulses

Hydrodynamic simulations are used to evaluate the potential of ultrashort laser pulses to localize energy at metallic surfaces, in our case aluminum. The emphasis is put on the dynamic sequence of laser energy deposition steps during the electron-ion nonequilibrium stage and the subsequent matter transformation phases. The simulations indicate correlated optical and thermodynamical states associated to specific electronic collisional mechanisms. The timescales of energy deposition deliver a guideline for using relevant relaxation times to improve the energy coupling into the material. We focus on a class of pump-probe experiments which investigate energy storage and particle emission from solids under ultrafast laser irradiation. Moreover, we have used our model to explain the experimentally observed optimization of energy coupling by tailoring temporal laser intensity envelopes and its subsequent influence on the ablation rate and on the composition of ablation products. Potential control for nanoparticle generation is discussed.     

Hawking radiation from ultrashort laser pulse filaments

Event horizons of astrophysical black holes and gravitational analogues have been predicted to excite the quantum vacuum and give rise to the emission of quanta, known as Hawking radiation. We experimentally create such a gravitational analogue using ultrashort laser pulse filaments and our measurements demonstrate a spontaneous emission of photons that confirms theoretical predictions.