Nonlinear increase in the energy input into a medium at the fusion of regularized femtosecond filaments

We consider dark matter consisting of long-living particles with masses 10⁷ GeV ? M ?10¹⁶ GeV decaying through hadronic channel as a source of high-energy neutrino. Using recent data on high-energy neutrino from IceCube and Pierre Auger experiments, we derive the upper-limits on neutrino flux from dark matter decay and constraints on dark matter parameter space. For the dark matter masses of order 10⁸ GeV the constraints derived are slightly stronger than those obtained for the same dark matter model using the highenergy gamma-ray limits.     

Majorons: A simultaneous solution to the large and small scale dark matter problems

It is shown that the existence of majorons, which enable a heavy neutrino, 500 eV ? m_νH ? 25 keV to decay into a light neutrino m_νL ? 8 eV and a majoron, with lifetime 10⁴ yr ? τ_νH ? 10⁸ yr can solve both the large and small scale dark matter problems. For a primordial “Zeldovich” spectrum of fluctuations the limits are $\text{m}{}_{\mathrm{<mtext>v</mtext><mtext>H</mtext>}}\text{?}\text{?}\text{550}\text{eV and}\text{τ}{}_{\mathrm{<mtext>v</mtext><mtext>H</mtext>}}$ > 10⁷ to 10⁸ yr (the ranges m_νH ? eV and τ_νH ? 10⁸ yr are allowed by the model but galaxy formation becomes problematic). The large scale dark matter problem is how to achieve the critical density as implied by inflation, the small scale problems deal with the halos of galaxies and galaxy formation and perturbation growth. The heavy neutrino could provide the solution to the small scale problem by initiating perturbation growth before decoupling. The decay products will be fast and thus not bound to the initial clumps, thus solving the large scale problem. The low mass relic neutrinos that were not decay products would remain bound in the gravitational potentials which grew from the initial perturbations. The resulting universe would be radiation dominated, which is consistent with present observations if H₀ ? 40 km/s/Mpc. An alternative solution can occur when m_νH ≈ 10 eV: the universe can again become matter dominated in the present epoch. This solution still allows H⁰ ～ 50 km/s/Mpc. The majoron model parameters which best fit the dark matter considerations are presented.     

A common origin of neutralino stars and supermassive black holes

To account for the microlensing events observed in the Galactic halo, Gurevich, Zybin, and Sirota have proposed a model of gravitationally bound, noncompact objects with masses of ～(0.01–1)M _⊙. These objects are formed in the expanding Universe from adiabatic density perturbations and consist of weakly interacting particles of dark matter, for example, neutralinos. They assumed the perturbation spectrum on some small scale to have a distinct peak. We show that the existence of this peak would inevitably give rise to a large number of primordial black holes (PBHs) with masses of ～10⁵ M _⊙ at the radiation-dominated evolutionary stage of the Universe. Constraints on the coefficient of nonlinear contraction and on the compactness parameter of noncompact objects were derived from constraints on the PBH number density. We show that noncompact objects can serve as gravitational lenses only at a large PBH formation threshold, δ_c > 0.5, or if noncompact objects are formed from entropic density perturbations.     

Mechanism of small variations in energy of ultracold neutrons interacting with a surface

The cause of the small heating of ultracold neutrons (UCNs) by ～10^?7 eV with a probability of 10^?8–10^?5 per collision with a surface was investigated. Neutrons heated in this way will be called vaporized UCNs (VUCNs). It was established that a preliminary heating of a sample in vacuum up to a temperature of 500–600 K can increase small-heating probability P _VUCN by a factor of at least ～100 and 10 on a stainless steel and a copper surface, respectively. For the first time, an extremely vigorous small heating of UCNs was observed on a powder of diamond nanoparticles. In this case, both the VUCN spectrum and the temperature dependence of probability P _VUCN were similar to those previously obtained for stainless steel, beryllium, and copper samples. On the surface of single crystal sapphire, neither the small heating of UCNs nor nanoparticles were found. All these facts indicate that VUCNs are likely produced by inelastic scattering of UCNs on weakly bound surface nanoparticles being in permanent thermal motion.     

Dark matter in galaxies and the growth of giant black holes

The relationship of dark matter to giant black holes (BHs) in galactic nuclei is investigated. The simultaneous evolution of dark and baryonic matter under the effect of an averaged self-consistent gravitational field is considered. The distribution of dark matter is shown to remain spherically symmetric even if there is an appreciable asymmetry in the distribution of baryonic matter in the galaxy. A kinetic equation that describes the evolution of the distribution function for dark matter with gravitational scattering by stars is derived. A significant flux of dark matter on a seed BHe at the galactic center is shown to arise under these conditions. The law of growth of the seed BH via the absorption of dark matter has been established. The seed BH is shown to grow significantly, up to 10⁷–10⁸ M⊙, in the lifetime of the galaxy. Observational data are briefly analyzed, and the presented theory has been found to be in reasonable agreement with experimental data.

     

Finite temperature behavior of gauge hierarchy models with quantum mechanical resuscitation

We investigate the finite temperature behavior of Dimopoulos and Georgi's hierarchy model where the grand unification scale M_G is naturally generated by the quantum corrections. Owing to the particular form, M²π²(e²lnπ ? 1), of the scalar potential, the first order GUT phase transition takes place at the critical temperature T_c ～ 10^9?12GeV much lower than M_G. If M_G should be of O(M_P) (Planck mass), the universe may undergo an inflationary stage to expand enough. Baryon number asymmetry might be produced by the decay of colored scalars with a mass of 10^10?12 GeV.     

The origin of double inflation

Double inflation is a typical solution of fourth-order gravity, $$L_{grav} = M^2 R - R^2 /6$$ minimally coupled to a scalar field with mass m, and 0pl. For equipartition of initial conditions at the Planck era, being equivalent to the Gibbons-Hawking-Stewart measure, we get the probability of double inflation to be about $$p = 1 - mM/M_{pl}^2 $$ Fort → ∞ and a scalar field or ideal fluid as source, the solutions for the scale factor oscillate around a～t^2/3, thus theR ² term gives effectively dustthe dark matter of the universe. The big bang is generically ofa ～ t^1/2 type, independent of the matter. ForM=0 and radiation as source the exact solutiona(t)=[sinh(2H ₀ t)]^1/2 supports the attractor property of the de Sitter solution.     

Heavy decaying dark matter and large-scale anisotropy of high-energy cosmic rays

We examine the role of the large-scale anisotropy of the high-energy cosmic ray distribution in a search for the heavy decaying dark matter (DM) signal. Using recent anisotropy measurements from the extensive air shower (EAS) observatories, we constrain the lifetime of the DM particles with masses 10⁷ ≤ M _X ≤ 10¹⁶ GeV. These constraints appear to be weaker than that obtained with the high-energy gamma-ray limits. We also estimate the desired precision level for the anisotropy measurements to discern the decaying DM signal marginally allowed by the gamma-ray limits and discuss the prospects of the DM search with the modern EAS facilities.     

Conversion of dark matter axions to photons in magnetospheres of neutron stars

We propose a new method to detect observational appearance of dark matter axions. The method utilizes radio observations of neutron stars. It is based on the conversion of axions to photons in strong magnetic fields of neutron stars (the Primakoff effect). If the conversion occurs, the radio spectrum of the object has a very distinctive feature—a narrow spike at the frequency corresponding to the rest mass of the axion. For example, if the coupling constant of the photon-axion interaction is M = 10¹⁰ GeV, the density of dark matter axions is ρ = 10⁻²⁴ g cm⁻³ and the axion mass is 5 μeV; then the flux from a strongly magnetized (10¹⁴ G) neutron star at the distance 300 pc from the Sun is expected to be about few tenths of millijansky at a frequency of about 1200 MHz in a bandwidth of about 3 MHz. Close-by X-ray dim isolated neutron stars are proposed as good candidates to look for such radio emission. The article is published in the original.     

Electric dipole moment of Dirac fermionic dark matter

The direct limit of electric dipole moment and direct searches for dark matter by electric dipole interaction are investigated with including the electromagnetic nuclear form factor, in case that the dark matter candidate is a Dirac particle. The electric dipole moment of dark matter constrained by direct searches must be lower than 7×¹⁰−22e cm for dark matter mass of 100 GeV to satisfy the current experimental exclusion limits at XENON10 and CDMS II. The CP violation of electric dipole moment and the dark matter discovery by electric dipole interaction in the future are considered.     

RX J0720.4-3125 as a possible example of magnetic field decay in neutron stars

We consider the possible evolution of the rotation period and magnetic field of the X-ray source RX J0720.4-3125, assuming that this source is an isolated neutron star accreting from the interstellar medium. The magnetic field of the source is estimated to be 10⁶–10⁹ G (the most probable value is about 2·10⁸ G), and it is difficult to explain the observed rotational period 8.38 s without invoking the hypothesis of magnetic field decay. For calculations we used the model of ohmic dissipation of the field in the core of the neutron star. Estimates for the accretion rate (10^?14–10^?16 M_⊙/yr), velocity of the source through the interstellar medium (10–50 km/s), and neutron star age (2·10⁹–10¹⁰ yrs) are obtained.     

Specific heat of NaNO2 near its transition points

Using an a.c. technique, the specific heat of NaNO₂ was measured as a function of temperature near its antiferroelectric-to-paraelectric phase transition point (T_N). The transition was found to be of the second order. The critical exponents are; α = 0·38 for ? = 2 × 10^?4 ～ 1 × 10^?1, and α′ = 0·18 for ? = ?2 × 10^?4 ～ ?3 × 10^?3. The critical exponents deduced from the scaling-law relations are roughly close to the values obtained from a random phase approximation for a system with an isotropic interaction. However, a difference was recognized between the observed exponent for the specific heat and the values theoretically given for T > T_N by the random phase approximation for a system with a short-range interaction or for a system with a long-range dipolar interaction. A thermodynamical analysis was made by using the generalized Pippard relation, and the present result was found to be consistent with the pressure dependence of the antiferroelectric transition point.     

Thermal properties and detectability of neutron stars - I cooling and heating of neutron stars

In this report, we first review earlier and recent developments in some of thermodynamic problems of neutron stars, especially those involving cooling mechanisms and theoretical predictions of surface temperatures of neutron stars. Emphasis is placed particularly on: the effect of equations of state and hence that of nuclear and strong interactions; the effect of better treatment of various neutrino cooling mechanisms, especially those involving pion condensates; and implication of these better and more detailed theoretical estimates on the prospect of directly observing thermal radiation from the surface of neutron stars. In connection with the last problem, we briefly review recent developments on the observational side — the HEAO-B and other programs already existing or expected to be planned for near future, which are directly related to the above problem. In connection with the possibilities of observing older neutron stars we briefly summarise various heating mechanisms.From these studies, we see that exciting possibilities exist through the HEAO-B and some other programs which may be realised in the 1980's, that we may observe radiation directly from neutron star surfaces if they are ? (3?5) × 10⁵°K. If such radiation is detected, the observed surface temperatures and further spectral studies may give invaluable insight into various important problems, such as magnetic properties of dense matter, equations of state, pion condensates, and other fundamental problems in nuclear, particle and high energy physics. If the surface temperatures of younger members of these stars (? 10⁴ years) are observationally found to be less than ≈ (5?10) × 10⁵°K (depending on the individual objects), we note that at the moment only pion coolings are consistent with observations, and the outcome may be equally far reaching. Among various observed neutron stars (pulsars) and neutron star candidates (e.g. supernova remnants), the Vela pulsar may prove to be the most rewarding one. If regular pulsar-like periodicities are discovered in radiations from any of supernova remnants, we can assume the presence of neutron stars in these objects. In that case, some supernova remnants, such as SN 1006, may also turn out to be promising. If we defect surface radiations from older pulsars (? 10⁵ years), that may support some of heating theories. At the end, we point out that there may be many point sources of very soft weak thermal X-rays across the sky (as old neutron stars accrete interstellar matter) and some of the closest ones may be detectable through the HEAO-B and similar devices.     

Revisiting pseudo-Dirac neutrinos

We study the pseudo-Dirac mixing of left- and right-handed neutrinos in the case where the Majorana masses M _L and M _R are small when compared with the Dirac mass, M _D . The light Majorana masses could be generated by a non-renormalizable operator reflecting effects of new physics at some high energy scale. In this context, we obtain a simple model independent closed bound for M _D . A phenomenologically consistent scenario is achieved with M _L ,M _R ≃10⁻⁷ eV and M _D ≃10⁻⁵–10⁻⁴ eV. This precludes the possibility of positive mass searches in the planned future experiments like GENIUS or in tritium decay experiments. If on the other hand, GENIUS does observe a positive signal for a Majorana mass ⩾10⁻³ eV, then with very little fine tuning of neutrino parameters, the scale of new physics could be in the TeV range, but pseudo-Dirac scenario in that case is excluded. We briefly discuss the constraints from cosmology when a fraction of the dark matter is composed of nearly degenerate neutrinos.     

Dipole moment and mobility of molecules in nematic liquid crystals of the 4-n-butyl ester of [4′-n-hexyloxyphenyl] benzoic acid in the absence of external orienting fields

Dielectric polarization was studied in a nematic liquid crystal of the 4-n-butyl ester of [4′-n-hexyloxyphenyl] benzoic acid (BE[HOP]BA) in the absence of external orienting fields in the isotropic and mesophase states in a frequency range of 10³–10⁷ Hz. In the isotropic melt, three regions of dielectric absorption of a relaxation origin were revealed. It is shown that two of them are related to a reorientation motion of individual molecules about the longitudinal axes (process I) and about the short axes (process II). Processes I and II have relaxation times τ ～ 10^?9 and 10^?8 s and activation energies ΔU ～ 16 and 23 kcal/mol, respectively; the energy of activation of process II in the liquid-crystal phase increases to ΔU ～ 38 kcal/mol. In the isotropic melt, in addition to processes I and II, process III occurs in the low-frequency range, which is characterized by greater relaxation times τ ～ 10^?7 s and an activation energy ΔU ～ 28 kcal/mol. In order to establish the nature of process III, temperature dependences of the dipole moments and Kirkwood correlation factor g were studied in both BE[HOP]BA phases. The magnitude of the Kirkwood factor in the isotropic phase of the BE[HOP]BA near the transition temperature from the mesomorphic state (g ～ 0.88) indicates the retention of the orientational ordering of molecules of the low-molecular liquid crystal and the compensation of their dipole moments intrinsic to the liquid-crystal state. This circumstance suggests that the third process of the relaxation of dipole polarization is due to a cooperative mode of motion of molecules in mesophase nuclei in the isotropic melt.     

Constraining a possible time variation of the gravitational constant through "gravitochemical heating" of neutron stars

A hypothetical time variation of the gravitational constant G would cause neutron star matter to depart from beta equilibrium, due to the changing hydrostatic equilibrium. This induces nonequilibrium beta processes, which release energy that is invested partly in neutrino emission and partly in internal heating. Eventually, the star arrives at a stationary state in which the temperature remains nearly constant, as the forcing through the change of G is balanced by the ongoing reactions. Using the surface temperature of the nearest millisecond pulsar, PSR J0437-4715, inferred from ultraviolet observations, we estimate two upper limits for this variation: (1) |.G/G|< 2 x 10(-10) yr(-1), if direct Urca reactions are allowed, and (2) |.G/G|< 4 x 10(-12) yr(-1), considering only modified Urca reactions. The latter is among the most restrictive obtained by other methods.     

Initiation of ecton processes by interaction of a plasma with a microprotrusion on a metal surface

Evolution of rapid (～10 ns) Ohmic overheating of a microprotrusion on a surface in contact with a plasma by emission current is studied taking into account the energy carried by plasma ions and electrons, as well as Ohmic heating, emissive source of energy release (Nottingham effect), and heat removal due to heat conduction. Plasma parameters were considered in the range of n = 10¹⁴?10²⁰ cm^?3 and T _e = 0.1 eV?10 keV. The threshold value of energy transferred to the surface from the plasma is found to be 200 MW/cm²; above this value, heating becomes explosive (namely, an increase in the temperature growth rate (δ² T/δt ² > 0) and in passing current (δJ/δt > 0) is observed in the final stage at T ～ 10⁴ K and j ～ 10⁸ A/cm²). In spite of the fact that Ohmic heating does not play any significant role for plasmas with a density lower than 10 18 cm^?3 because the current is limited by the space charge of electrons, rapid overheating of top of microprotrusion is observed much sooner (over a time period of ～1 ns) when the threshold is exceeded. In this case, intense ionization of vapor of the wall material leads to an increase in the plasma density at the surface, and the heating becomes of the Ohmic explosion type. Such conditions for the formation of a micr?xplosion on the surface and of an ecton accompanying it can be created during the interaction of a plasma with the cathode, anode, or an insulated wall and may lead to the formation of cathode and anode spots, as well as unipolar arcs.     

Search for strong gravitational lensing effect in the current GRB data of BATSE

Because gamma-ray bursts(GRBs)trace the high-z universe,there is an appreciable probability for a GRB to be gravitational lensed by galaxies in the universe.Herein we consider the gravitational lensing effect of GRBs contributed by the dark matter halos in galaxies.Assuming that all halos have the singular isothermal sphere(SIS)mass profile in the mass range 1010h?1M?M2×1013h?1M?and all GRB samples follow the intrinsic redshift distribution and luminosity function derived from the Swift LGRBs sample,we calculated the gravitational lensing probability in BATSE,Swift/BAT and Fermi/GBM GRBs,respectively.With an derived probability result in BATSE GRBs,we searched for lensed GRB pairs in the BATSE5B GRB Spectral catalog.The search did not find any convincing gravitationally lensed events.We discuss our result and future observations for GRB lensing observation.     

Gravity waves accompanying supernova explosions

Gravitational radiation arising during the formation of a protoneutron star is studied. Here it is mainly large-scale nonuniformities that develop inside the star. The entropy and density profiles of such nonuniformities resemble the “mushroom cloud” of a nuclear explosion. A bubble of hot neutron matter floats to the surface of the star, like the “mushroom cloud” of an explosion in the earth’s atmosphere. Depending on the symmetry of the problem, from two to six bubbles can float upward at the same time. The characteristic masses of such bubbles are 0.01M _⊗ and the radial velocities reach ∼0.1c. The energy radiated in the form of gravitational waves in one cycle of bubbles floating to the surface is ∼10⁻² M _⊗ c ²−10⁻¹⁰ M _⊗ c ². Such cycles occur repeatedly as the neutron star cools. This phase can last up to seconds. The total energy radiated in the form of gravitational radiation can reach 10⁻¹ M _⊗ c ². Pis’ma Zh. éksp. Teor. Fiz. 64, No. 12, 817–822 (25 December 1996)     

Neutron star magnetism

It is shown that

1. an appreciable change of magnetic moment of a neutron star cannot occur via ohmic dissipation
2. pulsars provide evidence for large internal magnetic fields in main sequence stars. If pulsars are born from stars with masses exceeding 3 ?_⊙ the internal field must be of the order of 10³-10⁴ Gauss while if they derived from less massive urstars 10² Gauss are sufficient to give rise to a magnetic moment ofM～10³⁰ Gauss cm³.