Adiabatically Compressed Research Articles

Adiabatically compressed wave dark matter halo and intermediate-mass-ratio inspirals

The adiabatic growth of a central massive black hole could compress the surrounding dark matter halo, leading to a steeper profile of the dark matter halo. This phenomenon is called adiabatic compression. We investigate the adiabatic compression of wave dark matter - a light bosonic dark matter candidate with its mass smaller than a few eV. Using the adiabatic theorem, we show that the adiabatic compression leads to a much denser wave dark matter halo similar to the particle dark matter halo in the semiclassical limit. The compressed wave halo differs from that of the particle halo near the center where the semiclassical approximation breaks down, and the central profile depends on dark matter and the central black hole mass as they determine whether the soliton and low angular momentum modes can survive over the astrophysical time scale without being absorbed by the black hole. Such a compressed profile has several astrophysical implications. As one example, we study the gravitational waves from the inspiral between a central intermediate-mass black hole and a compact solar-mass object within the wave dark matter halo. Due to the enhanced mass density, the compressed wave dark matter halo exerts stronger dynamical friction on the orbiting object, leading to the dephasing of the gravitational waves. The pattern of dephasing is distinctive from that of inspirals in the particle dark matter halo because of the difference in density profile and because of the relatively suppressed dynamical friction force, originating from the wave nature of dark matter. We investigate the prospects of future gravitational wave detectors, such as Laser Interferometer Space Antenna, and identify physics scenarios where the wave dark matter halo can be reconstructed from gravitational wave observations.

Finding evidence for inflation and the origin of galactic magnetic fields with CMB surveys

The origin of the $\mu$G magnetic fields observed in galaxies is unknown. One promising scenario is that magnetic fields generated during inflation, larger than 0.1 nG on Mpc scales, were adiabatically compressed to $\mu$G strengths in galaxies during structure formation. Thus, detecting a scale-invariant primordial magnetic field (PMF) above 0.1 nG on Mpc scales just after recombination would indicate an inflationary origin of galactic magnetic fields. This would also provide compelling evidence that inflation occurred since only an inflationary mechanism could generate such a strong, scale-invariant magnetic field on Mpc scales. In contrast, constraining the scale-invariant PMF strength to be below 0.1 nG would imply an inflationary scenario is not the primary origin, since such weak PMFs cannot be amplified enough via adiabatic compression to produce the strength of the galactic fields we observe today. We find that measurements of anisotropic birefringence by future CMB surveys will be able to improve the sensitivity to Mpc-scale inflationary PMFs by an order of magnitude, and, in particular, that CMB-HD would lower the upper bound to 0.072 nG at the 95% C.L., which is below the critical 0.1 nG threshold for ruling out a purely inflationary origin. If inflationary PMFs exist, we find that a CMB-HD survey would be able to detect them with about $3\sigma$ significance or higher, providing evidence for inflation itself.

The dependence of breakdown field upon breakdown delay time in adiabatically compressed ferroelectric ceramics

The ability of ferroelectric materials to generate high voltage under mechanical stress is widely used in transducer applications. The high strain-rate adiabatic compression of poled ferroelectrics results in their complete depolarization, the release of surface charges, and the generation of up to hundreds of kilovolts of electric potential that is an order of magnitude higher than in the low-strain piezoelectric mode. Electric breakdown within adiabatically compressed ferroelectric specimens is one of the factors that affect the generation of a high voltage by ferroelectric materials under extreme stress. We report herein the results of experimental investigations of the generation of high voltages by PbZr0.95Ti0.05O3 doped 2% Nb and PbZr0.52Ti0.48O3 doped 1% Nb2O5 poled ferroelectric ceramics adiabatically compressed by explosive-driven shock waves in a direction perpendicular to the direction of polarization. An important finding is the dependence of the ferroelectric breakdown field, Ebreak, upon breakdown delay time, td, for the two ferroelectrics, which is described by a power law: Ebreak(td) = β × td−η. This law can be used to characterize electric breakdown in adiabatically compressed ferroelectrics, for the prediction of voltage generated by ferroelectric materials under high strain rate loading, and for optimization of the ferroelectric materials properties for ultrahigh-power applications. The parameters of the power law indicate the possibility of an impulse thermal constituent in the mechanism for electric breakdown of adiabatically compressed ferroelectric ceramics. The Ebreak(td) relationships obtained in this study are important for theoretical consideration of mechanisms of breakdown in adiabatically compressed ferroelectrics and for ultrahigh-power applications of ferroelectric materials.

Extension of thickness-dependent dielectric breakdown law on adiabatically compressed ferroelectric materials

It is experimentally found that the Eb(d) = γ · d−ξ law describing the thickness-dependent breakdown electric field for solid dielectrics at ambient conditions can be extended for dielectrics in other thermodynamic states. It follows from the experimental results reported herein that the breakdown field, Eb(d), of Pb(Zr0.95Ti0.05)O3 (PZT 95/5) and Pb(Zr0.52Ti0.48)O3 (PZT 52/48) ferroelectrics subjected to explosive adiabatic compression obeys the above-mentioned law in a wide range of voltages, up to 150 kV.

Multistage Fusion Reaction Rates in an Adiabatically Compressed Plasma

We consider a dense gas of deuterium to undergo a rapid, adiabatic compression by a piston in a chamber. A reduction in the degrees of freedom of the plasma particles, such as may be effected by an electric discharge during the compression or by the application of magnetic fields, results in a higher final temperature for a given compression ratio. In model calculations we consider the adiabatic compression of one mole of molecular deuterium modeled as a van der Waals gas initially at room temperature and we compare the subsequent fusion energy release with the work done by the piston for various values of compression ratio and degrees of freedom. Prior work considered fusion to occur only at the end of the compression while the present work considers fusion energy released at various stages during the compression. Higher final temperatures and ratios of output to input energy result from this refinement of the model.

The Baryon Fractions and Mass‐to‐Light Ratios of Early‐Type Galaxies

We jointly model 22 early-type gravitational lens galaxies with stellar dynamical measurements using standard CDM halo models. The sample is inhomogeneous in both its mass distributions and the evolution of its stellar populations unless the true uncertainties are significantly larger than the reported measurement errors. In general, an individual system cannot constrain halo models, in the sense that the data poorly constrain the stellar mass fraction of the halo. An ensemble of systems, however, strongly constrains the average stellar mass represented by the visible galaxies to -->0.026 ± 0.006 of the halo mass if we neglect adiabatic compression, rising to -->0.056 ± 0.011 of the halo mass if we include adiabatic compression. Both estimates are significantly smaller than the global baryon fraction, corresponding to a star formation efficiency for early-type galaxies of 10%-30%. In the adiabatically compressed models, we find an average local B-band stellar mass-to-light ratio of -->(M/L)0 = 7.2 ± 0.5 M☉/L☉ that evolves as -->dlog (M/L)/dz = − 0.72 ± 0.08 per unit redshift. Adjusting the isotropy of the stellar orbits has little effect on the results. The adiabatically compressed models are strongly favored if we impose either local estimates of the mass-to-light ratios of early-type galaxies or weak-lensing measurements for the lens galaxies on 100 kpc scales as model constraints.

Cosmic ray feedback in hydrodynamical simulations of galaxy formation

It is well known that cosmic rays contribute significantly to the pressure of the interstellar medium in our own Galaxy, suggesting that they may play an important role in regulating star formation during the formation and evolution of galaxies. We here discuss a novel numerical treatment of the physics of cosmic rays and its implementation in the parallel smoothed particle hydrodynamics code GADGET-2. In our methodology, the non-thermal cosmic ray population of each gaseous fluid element is approximated by a simple power law spectrum in particle momentum, characterized by an amplitude, a cut-off, and a fixed slope. Adiabatic compression and a number of physical source and sink terms are modelled which modify the cosmic ray pressure of each particle. The most important sources considered are injection by supernovae and diffusive shock acceleration, while the primary sinks are thermalization by Coulomb interactions, and catastrophic losses by hadronic interactions. We also include diffusion of cosmic rays. Using a number of test problems, we show that our scheme is numerically robust and efficient, allowing us to carry out the first cosmological structure formation simulations that account for cosmic ray physics, together with radiative cooling and star formation. In simulations of isolated galaxies, we find that cosmic rays can significantly reduce the star formation efficiencies of small galaxies, with virial velocities below ~, an effect that becomes progressively stronger towards low-mass scales. In cosmological simulations of the formation of dwarf galaxies at high redshift, we find that the total mass-to-light ratio of small halos and the faint end of the luminosity function are affected. The latter becomes slightly flatter. When cosmic ray acceleration in shock waves is followed as well, we find that up to of the energy dissipated at structure formation shocks can appear as cosmic ray pressure at redshifts around , but this fraction drops to ~ at low redshifts when the shock distribution becomes increasingly dominated by lower Mach numbers. Despite this large cosmic ray energy content in the high-redshift intergalactic medium, the flux power spectrum of the Lyman-α forest is only affected on very small scales of , and at a weak level of . Within virialized objects, we find lower contributions of CR-pressure, due to the increased efficiency of loss processes at higher densities, the lower Mach numbers of shocks inside halos, and the softer adiabatic index of CRs, which disadvantages them when a composite of thermal gas and cosmic rays is adiabatically compressed. The total energy in cosmic rays relative to the thermal energy within the virial radius drops from 20% for halos to 5% for rich galaxy clusters of mass in non-radiative simulations. Interestingly, the lower effective adiabatic index also increases the compressibility of the intrahalo medium, an effect that slightly increases the central concentration of the gas and the baryon fraction within the virial radius. We find that this can enhance the cooling rate onto central cluster galaxies, even though the galaxies in the cluster periphery become slightly less luminous as a result of cosmic ray feedback.

Self-similar adiabatic compression of highly elongated field reversed configurations

A theoretical model of an elongated field reversed configuration (FRC) adiabatically compressed to high density by an imploding liner is presented. Compression is assumed to be self-similar, equal along length and radius, and is accomplished by means of a shaped liner. In particular, the model here takes into account the special magnetic topology of the FRC and the non-uniformity of the radial plasma profiles in order to quantify final to initial compression ratios of the fluid quantities.

Thermolysis of various energetic substances by exposure to adiabatically compressed gas

A transient thermal stimulus of 0.1 to 5.0 ms duration is delivered to the surface of a solid or liquid test substance by adiabatic compression and reexpansion of an inert gas. Pressures in the low...

Adiabatic compression of Schrödinger solitons due to the combined perturbations of higher-order dispersion and delayed nonlinear response.

We demonstrate for the first time that in a homogeneous nonamplifying physical system described by the nonlinear Schrodinger equation, the combined effects of the two different perturbations (delayed nonlinear response and higher-order dispersion) can lead to adiabatic compression of fundamental solitons. This is unexpected since each of these perturbations operating independently destroys soliton propagation. Experimentally this is demonstrated by showing that 95 fsec fundamental solitons are redshifted from 1.57 to 1.62 μm and adiabatically compressed to 55 fsec in 65 m of a single-mode silica fiber with modified dispersion

Adiabatic soliton compression of gain-switched DFB-LD pulse by distributed fiber Raman amplification

Using a dispersion-shifted single-mode fiber pumped by laser diodes as a distributed fiber Raman amplifier, the authors adiabatically compressed transform-limited (TL) pulses generated by a gain-switched distributed-feedback laser diode followed by linear compression and a spectral window. The initial TL pulses were successfully compressed asymptotically to almost pure solitons as short as 3.6 ps at the 2.4 dB total gain of a distributed fiber Raman amplifier, even without using solitons as the initial pulses. The experimental results are well supported by numerical calculations made with the beam propagation method. >

Explosions of adiabatically compressed gases in a constant volume bomb

Measurements of the explosion limits for fuel-air mixtures compressed by an expanding laminar flame front have been made in a constant volume bomb. The mixtures studied to date include normal pentane, hexane and heptane with fuel-air equivalence ratios in the range 0.8 to 1.3. An Arrhenius plot of the explosion density as a function of reciprocal temperature in the range 670 to 720 K is consistent with an activation energy of 51 kcal/mole. For fixed initial temperature and pressure the explosion density has a weak minimum at an equivalence ratio near =1.1 and decreases with increasing chain length. This behavior is in good agreement with observations made in rapid compression machines and spark ignition engines. A simple kinetic model based on a branched chain mechanism has been developed to correlate the data. In the first stage region the equations are linear and can be integrated approximately using the WKB method. The resulting expression gives an explicit connection between the explosion limit for gases undergoing adiabatic compression and the first stage induction time at constant density. Quantitative agreement between theory and experiment can be achieved with minor modifications in values of published rate constants.

Initiation of fast reactions in oxidant-fuel mixtures

The initiation conditions for inhomogenous explosive systems are very much affected by the ignition of the grains from the surface by adiabatically compressed gas. Previous examination of the detonation capacity of mixtures of APC with TNT considered only the poured powder density, for particle sizes that differed only slightly. This paper examines the detonation capacity of stoichiometric mixtures of crushed TNT and APC with two crystal sizes using the same batches as in the impact experiments in order to examine the effects of charge density. The results indicate that the main source of reaction foci when the porosity is high is provided by adiabatic compression of air inclusions in the pores, with particle ignition virtually over the entire surface. Because of this it is impossible to compare the initiation mechanisms of shock waves on porous mixtures to oxygen-fuel mixtures mechanical initiations.

Branched-chain mechanism of propane-oxygen-fluorineexplosions

Fluorine diluted with inert gas is injected into a mixture of propane, oxygen, and inert gas at room temperature and the temperature is increased rapidly by adiabatic compression; or, using the same apparatus, a mixture of propane, oxygen, and inert gas is adiabatically compressed, and diluted fluorine is injected into the compressed gas within less than a millisecond. The molecular concentrations and the temperature of the mixture at the end of the compression stroke are determined by the compression ratio, the mixture composition, and the initial pressure and temperature. The compression temperature is calculated from the entropy of the mixture, using thermodynamic tables. It is found that the reaction terminates in explosion between a lower and an upper limit of the concentration ratio [F 2 ]/[O 2 ]. Both limits have been reproduced in numerous runs. The limits coincide at about 350°K and diverge toward higher temperatures, enclosing an explosion peninsula in a diagram of [F 2 ]/[O 2 ] versus temperature. The limits are not significantly dependent on the method of experimentation. They are insensitive to changes of the propane concentration and also to changes of the pressure, if the latter exceeds a critical limit. The critical limit of the concentration ratio [F 2 ]/[O 2 ] corresponds to the scheme C 3 H 7 + O 2 = C 3 H 7 O O , ( 1 ) C 3 H 7 + F 2 → c h a i n b r e a k i n g , ( 2 ) C 3 H 7 O O + F 2 → n C 3 H 7 , ( a ) C 3 H 7 O O + O 2 → c h a i n b r e a k i n g . ( b ) From reaction-kinetic theory, the explosion peninsula is described by the equation y = ( x − 1 ) ( 1 ± { 1 − [ 2 x / ( x − 1 ) 2 ] } 1 / 2 ) where [with 3 C 3 H 7 in Reaction (a)] x = 2 k 1 k a / k 2 k b = C 1 exp [ − ( E 1 − E 2 + E a − E b ) / R T ] , y = 2 k a [ F 2 ] / k b [ O 2 ] = C 2 ( [ F 2 ] / [ O 2 ] ) exp [ − ( E a − E b ) / R T ] . A close fit between the experimental curve [F 2 ]/[O 2 ] versus T and the theoretical curve of y versus x is obtained using C 1 = 23.7 E 1 − E 2 = 3810 cal/ mole, C 2 = 1.74 E a − E b = − 2520 cal/ mole. The validity extends to about 700°K.

Ignition Caused by the Adiabatic Compression of Air in Contact with a Lubricating-Oil-Wetted Surface

A pneumatically operated rapid compression machine is used to study the conditions under which ignition will occur when air in contact with a lubricating-oil-wetted surface is adiabatically compressed. The boundaries and violence of explosion are determined from pressure measurements made during and after compression. The specific variables investigated are initial temperature, compression ratio, oil volume, and oil type. The maximum oil temperature and compression ratio investigated are 210°C and 31/1 respectively. Several concentrations of three mineral oils are considered. In order to calculate liquid-vapour equilibrium of the lubricating oils, vapour pressure-weight loss data obtained by a flame ionization method are employed in conjunction with the carbon number distribution analysis of the lubricating oil components. The calculation of oil-air equivalence ratios in the vapour phase leads to the prediction of the effect of oil concentration and of temperature on ignition hazards. The prediction is in good agreement with experimental findings and accounts for the influence of temperature on ignition. For example, it was found that ignition occurs at 120°C for compression ratio of 31/1 but will not take place until the system is heated to 160°C for a compression ratio of 18/1.