Effect Of Pair Creation Research Articles

Fission and fusion of heavy nuclei induced by the passage of a radiation-mediated shock in BNS mergers

ABSTRACT We compute the structure of a Newtonian, multi-ion radiation-mediated shock (RMS) for different compositions anticipated in various stellar explosions. We use a multifluid RMS model that incorporates electrostatic coupling between the different plasma constituents as well as Coulomb friction in a self-consistent manner, and approximates the effect of pair creation and the presence of free neutrons in the shock upstream on the shock structure. We find that under certain conditions a significant velocity separation is developed between different ions in the shock downstream and demonstrate that in fast enough shocks ion–ion collisions may trigger fusion and fission events at a relatively high rate. Our analysis ignores anomalous coupling through plasma microturbulence, which might reduce the velocity spread downstream below the activation energy for nuclear reactions. A rough estimate of the scale separation in RMS suggests that for shocks propagating in binary neutron star (BNS) merger ejecta, the anomalous coupling length may exceed the radiation length, allowing a considerable composition change behind the shock via inelastic collisions of $\alpha$ particles with heavy elements at shock velocities $\beta _\mathrm{ u}\gtrsim 0.25$. A sufficient abundance of free neutrons in the shock upstream, as expected during the first second after the merger, is also expected to alter the ejecta composition through neutron capture downstream. The resultant change in the composition profile may affect the properties of the early kilonova emission. The generation of microturbulence due to velocity separation can also give rise to particle acceleration that might alter the breakout signal in supernovae and other systems.

Threshold corrections of χc(2P) and χb(3P) states and J/ψρ and J/ψω transitions of the X(3872) in a coupled-channel model

We calculate the masses of χc(2P) and χb(3P) states with threshold corrections in a coupled-channel model. Here, the meson quarkonium core is augmented by higher Fock components due to pair-creation effects. According to our results, we interpret the resonances characterized by very small threshold corrections, like χb(3P)'s, as almost pure quarkonia, and those states characterized by non-negligible threshold corrections, like the X(3872), as quarkonium cores plus meson–meson components. We also study the J/ψρ and J/ψω hidden-flavor strong decays of the X(3872). The decays are calculated as the dissociation of one of these components (D0D¯0⁎) into a cc¯ state (J/ψ) plus a light meson (ρ or ω) in a potential model. In particular, our result for the ratio between the X(3872)→J/ψω and J/ψρ widths (0.6) is compatible with the present experimental data (0.8±0.3) within the experimental error.

Self-energies of octet and decuplet baryons due to the coupling to the baryon-meson continuum

We present an unquenched quark model calculation of the mass shifts of ground-state octet and decuplet baryons due to the coupling to the meson-baryon continuum. All ground-state baryons and pseudoscalar mesons are included in our calculation as intermediate states. The $q\bar{q}$ pair creation effects are taken explicitly into account through a microscopic, QCD-inspired, quark-antiquark pair creation mechanism.

Scalar and fermion representations of the Lorentz group in Minkowski plane, QFT correlators, pair creation in electric field and the Unruh effect

Boost modes [Formula: see text] are eigenfunctions of the Lorentz transformations generator in two-dimensional (2D) Minkowski space (MS). We demonstrate and discuss deep interrelation between the boost modes and the field correlators, also known as Wightman functions. In the case of a massive scalar field, the boost modes, as functions of the spectral parameter [Formula: see text], contain the Dirac delta-function singularity [Formula: see text] at the light cone. The zero boost mode coincides up to a constant factor with the Wightman function. The light cone singularity of boost modes for a fermion field is stronger. For this case, they contain the Gelfand [Formula: see text]-function of complex argument [Formula: see text], while the Wightman function components coincide with analytical continuation of the boost modes set towards the spectral values [Formula: see text]. We argue that due to the discovered properties of the boost modes the so-called Unruh modes, which are at the core of the Unruh effect derivation, do not constitute a complete set in MS and thus cannot be used for quantization of neither scalar, nor fermion field. Finally, we discuss boost modes for the case of the constant electric background and rederive the well-known result for spontaneous pair creation rate. Solution of this problem in the boost modes representation reveals distinctions between the Unruh problem and the effect of pair creation by an electric field in vacuum.

Effective temperature of nonequilibrium dense matter in holography

We study properties of effective temperature of nonequilibrium steady states by using the anti--de Sitter spacetime/conformal field theory ($\mathrm{AdS}/\mathrm{CFT}$) correspondence. We consider nonequilibrium systems with a constant flow of current along an electric field, in which the current is carried by both the doped charges and those pair created by the electric field. We find that the effective temperature agrees with that of the Langevin systems if we take the limit where the pair creation is negligible. The effect of pair creation raises the effective temperature whereas the current by the doped charges contributes to lower the effective temperature in a wide range of the holographic models.

Creation of electron-positron plasma with superstrong laser field

We present a short review of recent progress in studying QED effects within the interaction of ultra-relativistic laser pulses with vacuum and e − e + plasma. Current development in laser technologies promises very rapid growth of laser intensities in the near future. Two exawatt class facilities (ELI and XCELS, Russia) in Europe are already in the planning stage. Realization of these projects will make available a laser intensity of ∼ 1026 W/cm2 or even higher. Therefore, discussion of nonlinear optical effects in vacuum are becoming compelling for experimentalists and are currently gaining much attention. We show that, in spite of the fact that the expected field strength is still essentially less than E S = m 2 c 3/eℏ = 1.32 · 1016 V/cm, the nonlinear vacuum effects will be accessible for observation at the ELI and XCELS facilities. The most promissory effect for observation is pair creation by a laser pulse in vacuum. It is shown, that at intensities ∼ 5 · 1025 W/cm2, creation even of a single pair is accompanied by the development of an avalanche QED cascade. There exists a distinctive feature of the laser-induced cascades, as compared with the air showers arising due primarily to cosmic rays entering the atmosphere. In our case the laser field plays not only the role of a target (similar to a nucleus in the case of air showers) but is also responsible for the acceleration of slow particles. It is shown that the effect of pair creation imposes a natural limit for the attainable laser intensity and, apparently, the field strength E ∼ E S is not accessible for a pair-creating electromagnetic field at all.

Schwinger pair creation in constant and time-dependent fields

The effect of pair creation from the vacuum in a strong electric field, predicted by Schwinger in 1951, may conceivably be confirmed experimentally with some of the ultrastrong lasers presently under construction. However, it is not easy to calculate the effect for realistic laser fields. We will shortly review here the intermediate case of a purely time-dependent but otherwise generic electric field, which is still relatively amenable to calculation.

Amplifying the Hawking Signal in BECs

We consider simple models of Bose-Einstein condensates to study analog pair-creation effects, namely, the Hawking effect from acoustic black holes and the dynamical Casimir effect in rapidly time-dependent backgrounds. We also focus on a proposal by Cornell to amplify the Hawking signal in density-density correlators by reducing the atoms’ interactions shortly before measurements are made.

THE ROLE OF A DYNAMICAL MEASURE AND DYNAMICAL TENSION IN BRANE CREATION AND GROWTH

The use of a non-Riemannian measure of integration in the action of strings and branes allows the possibility of dynamical tension. In particular, lower dimensional objects living in the string/brane can induce discontinuities in the tension: the effect of pair creation on the string tension is studied. We then investigate the role that these new features can play in string and brane creation and growth. A mechanism is studied by means of which a scalar field can transfer its energy to the tension of strings and branes. An infinite-dimensional symmetry group of this theory is discussed. Creation and growth of bubbles in a formulation that requires mass generation for the bulk gauge fields coupled to the branes is also discussed.

Formula omitted]-pair production by a focused laser pulse in vacuum

The probability of electron–positron pair creation by a focused laser pulse is calculated. For description of the focused laser pulse we use a 3-dimensional model of the electromagnetic field which is based on an exact solution of Maxwell equations. There exists two types of focused waves: e- and h-polarized waves with only either electric, or magnetic vector being transverse respectively. It is shown that pair production is possible only in e-polarized electromagnetic wave. The dependence of the pair production probability on the intensity of the laser pulse is obtained. It is argued that there exists a natural physical limit for attainable focused laser pulse intensities. This limit is posed by the pulse energy loss due to the effect of pair creation.

Numerical simulations of aligned neutron star magnetospheres

ABSTRA C T We present detailed numerical simulations of the magnetosphere of an isolated neutron star in which the spin and magnetic dipole axes of the star are aligned. We demonstrate that stable charge distributions are always found, rather than particle outflows. A stable magnetosphere consists of a dome above the polar cap containing plasma of one charge and an equatorial belt containing plasma of the other sign: E · Ba 0 inside both of these. These are separated by a vacuum gap in which E · B ‐ 0Ora 0 instead). We show that the charge distribution used in the ‘standard’ Goldreich‐Julian pulsar model is inherently unstable: it collapses to a stable configuration that is very similar to the others illustrated here. An instructive video of this collapse is available at http://spacsun.rice.edu/,ian/. For typical pulsars, the stable solution has no particles near to the light cylinder, and if there were any there then their loss from the system would not lead to a replacement from the star (in contradiction to the explicit assumption used in the Goldreich‐Julian model). We discuss the generic effects of pair creation, in particular as an additional source of ionization in the vacuum gap. The overall effect is simply to reduce the value of E · B in the vacuum gap so that the pair-production rate drops towards zero. A dome, disc and gap geometry is still the resulting solution. In conclusion, we confirm previous studies that the aligned rotator cannot make an active pulsar.

Effects of pair creation on charged gravitational collapse

We investigate the effects of pair creation on the internal geometry of a black hole, which forms during the gravitational collapse of a charged massless scalar field. Classically, strong central Schwarzschild-like singularity forms, and a null, weak, mass-inflation singularity arises along the Cauchy horizon, in such a collapse. We consider here the discharge, due to pair creation, below the event horizon and its influence on the {\it dynamical formation} of the Cauchy horizon. Within the framework of a simple model we are able to trace numerically the collapse. We find that a part of the Cauchy horizon is replaced by the strong space-like central singularity. This fraction depends on the value of the critical electric field, $E_{\rm cr}$, for the pair creation.

Effect of color screening on heavy quarkonia Regge trajectories

Using an unquenched lattice potential to calculate the spectrum of a bottomonium-like system, we demonstrate numerically that the effect of pair creation is to produce termination of the real part of hadronic Regge trajectories, in contrast to the Veneziano model and the vast majority of phenomenological generalizations. Termination of the real part of Regge trajectories may have significant experimental consequences.

Bare Quark Matter Surfaces of Strange Stars ande+e−Emission

We show that the Coulomb barrier at the quark surface of a hot strange star may be a powerful source of ${e}^{+}{e}^{\ensuremath{-}}$ pairs which are created in an extremely strong electric field of the barrier and flow away from the star. The luminosity in the outflowing pair plasma depends on the surface temperature ${T}_{\mathrm{S}}$ and may be very high, up to $\ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}{10}^{51}\mathrm{ergs}{\mathrm{s}}^{\ensuremath{-}1}$ at ${T}_{\mathrm{S}}\ensuremath{\sim}{10}^{11}\mathrm{K}$. The effect of pair creation by the Coulomb barrier may be a good observational signature of strange stars which can give an answer to the question of whether a compact object is a neutron or strange star.

QCD1+1 in the limit of a large number of colors and flavors

QCD in 1+1 dimensions is examined in the limit of a large number of colors and flavors. The Hamiltonian matrix is given in a Fock space spanned by 't Hooft meson states and, for the case of zero fermion mass, a submatrix is diagonalized numerically to give the low-lying spectrum as a function of N F / N C . Pair creation effects generate bound states which are complicated mixtures of components of different meson number. There are a number of nontrivial zero modes; in the massive part of the spectrum some states tend to a well-defined N F ⪢ N C limit while others become unstable and disappear. The masses of most states remain remarkably constant over a large range of N F / N C .

Nonequilibrium quantum fields in the large-N expansion.

An effective action technique for the time evolution of a closed system consisting of one or more mean fields interacting with their quantum fluctuations is presented. By marrying large-N expansion methods to the Schwinger-Keldysh closed time path formulation of the quantum effective action, causality of the resulting equations of motion is ensured and a systematic, energy-conserving and gauge-invariant expansion about the quasiclassical mean field(s) in powers of 1/N developed. The general method is exposed in two specific examples, O(N) symmetric scalar \ensuremath{\lambda}${\mathrm{\ensuremath{\Phi}}}^{4}$ theory and quantum electrodynamics (QED) with N fermion fields. The \ensuremath{\lambda}${\mathrm{\ensuremath{\Phi}}}^{4}$ case is well suited to the numerical study of the real time dynamics of phase transitions characterized by a scalar order parameter. In QED the technique may be used to study the quantum nonequilibrium effects of pair creation in strong electric fields and the scattering and transport processes in a relativistic ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$ plasma. A simple renormalization scheme that makes practical the numerical solution of the equations of motion of these and other field theories is described.

Quark-antiquark pair creation effects in the study of S = 0 and S = −1 baryons

Improved wavefunctions of non-strange and strange baryons are obtained by incorporating quark-antiquark excitations inherent in the quark-gluon interaction into the quark model. The working framework is the shell model where the antiquark is assigned an intrinsic parity quantum number to distinguish it from the quark. The parameters of the interaction are chosen to be consistent with the experimental data. It is found that the amplitudes of the 3 q( q q) and 3 q( q 2 q 2 ) components are not negligible and should be included in the calculation of the properties of the baryons. It is also found that the amplitude of the 3 q( q q) component for strange baryons is less than for nonstrange ones, indicating that the hyperon-nucleon(-hyperon) interaction is less attractive than the NN one.

Quenched approximation in the quark model.

We present a model calculation of some effects of virtual {ital q{bar q}} pairs in mesons. Specifically, using a model for pair creation that has previously been shown to give a good description of strong meson decays, we calculate the energy shift of a static quark-antiquark pair due to the presence of virtual quark-antiquark pairs. The shift is large and approximately proportional to the distance between the static sources. The linearity of the correction suggests that pair-creation effects can be absorbed into a renormalization of the mesonic string tension. However, this masking can only be approximate, as we show by considering the dependence of the energy shift on the spin state of the sources. We conclude by pointing out the relevance of our results to the {ital N}/{rho}'' problem encountered in lattice QCD calculations.

N̄N annihilation into one meson and meson decay into two or three mesons in the 3P 0 model

The coupling constants and the form factor of N̄N annihilation into one meson are calculated in the 3P 0 model. This allows one to estimate the one-meson annihilation potential for the NN system and to give information on the effect of pair creation in the nucleus. The form factor of relative S-wave N̄N coupling to an s-wave meson has a zero at t-value around 5 GeV 2 but the relative D-wave N̄N coupling to a meson decreases slower than that of S-wave and the sign does not change. We study in the same framework the decay of a meson into two or three mesons. The decay widths of ω,ρ, ε, B and A 1 are calculated. The decays of ω, A 1 and virtual π into three π are also studied. We include the final-state interaction by multiplying the amplitude of ππ scattering on the three-meson production amplitudes. The model is tested in the Dalitz-plot distribution of three pions in the decay of A 1 meson production from τ. The selection rules that are obtained from the annihilation model A2, in which a ρ is treated as a qq̄, and from the annihilation model A3, in which a ρ is the two π interacting in the final state are compared, and the experimental data of N N annihilation into mesons and meson decay into mesons are discussed.

Pair-creation effects in accretion-shock models of active galactic nuclei

view Abstract Citations (9) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Pair-Creation Effects in Accretion Shock Models of Active Galactic Nuclei Blondin, John M. ; Konigl, Arieh Abstract An exploration is undertaken of the possibility that the copious production of e(+)e(-) pairs that is expected to occur in AGNs with large compactness parameters may have an important effect on the structure of the accretion shock that may form near the central black hole in these sources. If the pairs are well coupled to the inflowing plasma, they could generate a substantial decrease in the effective value of the Eddington luminosity within the shock, and the radiation generated within the shock could play a substantial role in flow deceleration and thermalization even when the measured luminosity is far below the nominal Eddington value. The effect is demonstrated by a simple model of a planar shock that is mediated by Fermi-accelerated relativistic protons and radiation. Publication: The Astrophysical Journal Pub Date: December 1987 DOI: 10.1086/165842 Bibcode: 1987ApJ...323..451B Keywords: Active Galactic Nuclei; Astronomical Models; Black Holes (Astronomy); Galactic Radiation; Shock Wave Propagation; Astronomical Spectroscopy; Electron-Positron Pairs; Elementary Particles; Equilibrium Flow; X Ray Spectroscopy; Astrophysics; BLACK HOLES; ELEMENTARY PARTICLES; GALAXIES: NUCLEI; SHOCK WAVES; RADIATION MECHANISMS full text sources ADS |