Dense Baryonic Matter Research Articles

Vlasov description of dense quark matter

We discuss properties of quark matter at finite baryon densities and zero temperature in a Vlasov approach. We use a screened interquark Richardson's potential consistent with the indications of lattice QCD calculations. We analyze the choices of the quark masses and the parameters entering the potential which reproduce the binding energy of infinite nuclear matter. There is a transition from nuclear to quark matter at densities five times above normal nuclear matter density. The transition could be revealed from the determination of the position of the shifted meson masses in dense baryonic matter. A scaling form of the meson masses in dense matter is given.

Cosmological parameters from cluster abundances, cosmic microwave background and IRAS

We combine information on cosmological parameters from cluster abundances, CMB primordial anisotropies and the IRAS 1.2-Jy galaxy redshift survey. We take as free parameters the present values of the total matter density of the universe, Ωm, the Hubble parameter, h, the linear theory rms fluctuations in the matter density within 8 h−1 Mpc spheres, σ8, and the IRAS biasing factor, bIRAS. We assume that the universe is spatially flat, with a cosmological constant, and that structure formed from adiabatic initial fluctuations with a Harrison–Zel'dovich power spectrum (i.e. the primordial spectral index n=1). The nucleosynthesis value for the baryonic matter density Ωb=0.019/h2 is adopted. We use the full three- and four-dimensional likelihood functions for each data set and marginalize these to two- and one-dimensional distributions in a Bayesian way, integrating over the other parameters. It is shown that the three data sets are in excellent agreement, with a best-fitting point of Ωm=1-ΩΛ=0.36,h=0.54,σ8=0.74, and bIRAS=1.08. This point is within one sigma of the minimum for each data set alone. Pairs of these data sets have their degeneracies in sufficiently different directions that using only two data sets at a time is sufficient to place good constraints on the cosmological parameters. We show that the results from each of the three possible pairings of the data are also in good agreement. Finally, we combine all three data sets to obtain marginalized 68 per cent confidence intervals of 0.30<Ωm<0.43,0.48<h<0.59,0.69<σ8<0.79, and 1.01<bIRAS<1.16. For the best-fitting parameters the CMB quadrupole is Qrms-ps=18.0 μK, the shape parameter of the mass power spectrum is Γ=0.15, the baryon density is Ωb=0.066 and the age of the universe is 16.7 Gyr.

Model Study of Hot and Dense Baryonic Matter

The properties of baryonic matter have been investigated at finite density and temperature using different models. The variation of baryon masses and fractional number densities with baryon density and temperature obtained from different models have been compared. The quark hadron phase transition have been studied using Chiral Colour Dieletric (CCD) model in the quark sector. No phase transition have been observed for the different variants of the Zimanyi-Moszkowski models below T=60 MeV.

The critical points of strongly coupled lattice QCD at nonzero chemical potential

We study QCD at nonzero quark density, zero temperature, infinite coupling using the Glasgow algorithm. An improved complex zero analysis gives a critical point ${\ensuremath{\mu}}_{c}$ in agreement with that of chiral symmetry restoration computed with strong coupling expansions, and monomer-dimer simulations. We observe, however, two unphysical critical points: the onset for the number density ${\ensuremath{\mu}}_{0}$, and ${\ensuremath{\mu}}_{s}$ the saturation threshold, coincident with pathological onsets observed in past quenched QCD calculations. An analysis of the probability distributions for particle number supports our physical interpretation of the critical point ${\ensuremath{\mu}}_{c},$ and offers a new intepretation of ${\ensuremath{\mu}}_{0}$, which confirms its unphysical nature. The perspectives for future lattice QCD calculations of the properties of dense baryonic matter are briefly discussed.

The Opacity of the Lyα Forest and Implications for Ωband the Ionizing Background

We have measured the distribution function of the flux decrement D = 1 - e-τ caused by Lyα forest absorption from intervening gas in the lines of sight to high-redshift QSOs from a sample of seven high-resolution QSO spectra obtained with the Keck telescope. The observed flux decrement distribution function (FDDF) is compared with the FDDF from two simulations of the Lyα forest: a ΛCDM model (with Ω = 0.4, Λ = 0.6), computed with the Eulerian code of Cen & Ostriker, and a standard cold dark matter (SCDM) model (with Ω = 1), computed with the smoothed particle hydrodynamics code of Hernquist et al. Good agreement is obtained between the shapes of the simulated and observed FDDFs for both simulations after fitting only one free parameter, which controls the mean flux decrement. The difference between the predicted FDDFs from the two simulations is small, and we show that it arises mostly from a different temperature in the low-density gas (caused by different assumptions that were made about the reionization history in the two simulations), rather than differences between the two cosmological models or numerical effects in the two codes, which use very different computational methods. A measurement of the parameter μΩ -->2b h -->3/Γ (where Γ is the H I ionization rate due to the ionizing background) is obtained by requiring the mean flux decrement in the simulations to agree with the observed one. Estimating the lower limit Γ > 7 × 10-13 s-1 from the abundance of known QSOs, we derive a lower limit on the baryonic matter density, Ωbh2 > 0.021 (0.017) for the ΛCDM (SCDM) model. The difference between the lower limits inferred from the two models is again due to different temperatures in the low-density gas. We give general analytical arguments for why this lower limit is unlikely to be reduced for any other models of structure formation by gravitational collapse that can explain the observed Lyα forest. When combined with constraints from big bang nucleosynthesis, the large Ωb we infer is inconsistent with some recent D/H determinations (Rugers & Hogan), favoring a low deuterium abundance as reported by Tytler, Fan & Burles. Adopting a fixed Ωb, the measurement of μ(z) allows a determination of the evolution of the ionizing radiation field with redshift. Our models predict an intensity that is approximately constant with redshift, which is in agreement with the assumption that the ionizing background is produced by known quasars for z < 3, but requires additional sources of ionizing photons at higher redshift given the observed rapid decline of the quasar abundance.

Effective kaon mass in dense baryonic matter: role of correlations

We evaluate the effective kaon mass in dense nuclear matter. Pauli blocking and nucleon-nucleon short-range correlations are incorporated. The effects of short-range correlations are shown to be moderate and figure importantly only at densities larger than 2 times normal nuclear density. We discuss the relations between the present results and the results obtained in next-to-next-to-leading order chiral perturbation theory ( O(Q 3), where Q is the characteristic small energy-momentum scale probed). We also discuss mean-field aspects, with some remarks on the relation between the short-range correlations and the four-Fermi contact terms in the chiral effective Lagrangian.

Evolution of Structure in the Intergalactic Medium and the Nature of the Lyα Forest

We have performed a detailed statistical study of the evolution of structure in a photoionized intergalactic medium (IGM) using analytical simulations to extend the calculation into the mildly nonlinear density regime found to prevail at z = 3. Our work is based on a simple fundamental conjecture: that the probability distribution function of the density of baryonic diffuse matter in the universe is described by a lognormal (LN) random field. The LN distribution has several attractive features and follows plausibly from the assumption of initial linear Gaussian density and velocity fluctuations at arbitrarily early times. Starting with a suitably normalized power spectrum of primordial fluctuations in a universe dominated by cold dark matter (CDM), we compute the behavior of the baryonic matter, which moves slowly toward minima in the dark matter potential on scales larger than the Jeans length. We have computed two models that succeed in matching observations. One is a nonstandard CDM model with OMEGA = 1, h = 0.5, and GAMMA = 0.3, and the other is a low-density flat model with a cosmological constant (LCDM), with OMEGA = 0.4, OMEGA(sub LAMBDA) = 0.6, and h = 0.65. In both models, the variance of the density distribution function grows with time, reaching unity at about z = 4, where the simulation yields spectra that closely resemble the Ly-alpha forest absorption seen in the spectra of high-z quasars. The calculations also successfully predict the observed properties of the Ly-alpha forest and their evolution from z = 4 down to at least z = 2, assuming a constant intensity for the metagalactic UV background over this redshift range. However, in our model the forest is not due to discrete clouds, but rather to fluctuations in a continuous intergalactic medium. At z = 3; typical with measured neutral hydrogen column densities N(sub H I) = 10(exp 13.3), 10(exp 13.5), and 10(exp 11.5) /sq cm correspond to fluctuations with mean total densities approximately 10, 1, and 0.1 times the universal mean baryon density. Perhaps surprisingly, fluctuations whose amplitudes are less than or equal to the mean density still appear as clouds because in our model more than 70% of the volume of the IGM at z = 3 is filled with gas at densities below the mean value.

On the possibility of the condensation of the charged rho-meson field in dense isospin asymmetric baryon matter

It is shown that at sufficiently large density the isospin-asymmetric baryon matter may undergo the phase transition to the p-condensate state being characterized by the finite values of the charged p-meson mean fields. The appearance of such a condensate diminishes the asymmetry energy of the baryon matter. It is shown that in the neutron stars the corresponding phase transition is of the first order. Possible consequences are enumerated.

Hadrons in dense baryonic matter

Hadrons in dense baryonic matter

New Measurements of Ancient Deuterium Boost the Baryon Density of the Universe

A side from ordinary hydrogen, only four other nuclear species (2H, 3He, 4He and 7Li are left over from the Big Bang. Of these, deuterium (2H) is the one whose obsei^ved abundance provides the most accurate determination of the crucial cosmological parameter ρb, the present‐day average mass density of ordinary baryonic matter (made up of protons and neutrons) in the universe. In principle, if one knows the primordial abundance of any one of these light nuclei, relative to 1H, the theory of Big Bang nucleosynthesis specifies ρb. (See the figure below.)

Nonsingular decaying-vacuum cosmology and baryonic matter

A nonsingular closed universe model with continuous creation of radiation or matter from the vacuum is introduced. Although primordial nucleosynthesis in this model follows the standard scenario it does not require the density of baryonic matter to be well below the critical density as in standard cosmology. The model predicts a present vacuum energy comparable with the matter energy. Its predictions for the classical low red-shift cosmological tests agree with the standard flat model results.

Scaled effective chiral lagrangians for the propagation of scalar and vector mesons in dense matter

We explore various chiral lagrangians in which the QCD scale anomaly is implemented by introducing a dilaton field representing the gluon condensate. The lagrangians are used to study the chiral phase transition and the propagators of both scalar and vector mesons in dense baryonic matter. A hybrid model is proposed which allows an unambiguous definition of meson masses and coupling constants in dense matter. Meson masses are calculated as a function of density.

Effect of the vector-axial-vector coupling on the vector-meson modes

We investigate the effect of the coupling between the vector and the axial-vector fields on the vector-meson time-like modes in a dense baryonic matter. We show that, in the Nambu-Jona-Lasinio model, the ρ and a 1 transverse modes couple together. This mixing is responsible for a small splitting in the ω and ρ transverse propagation modes at high density and high momentum.

Effective kaon mass in baryonic matter and kaon condensation

The effective kaon mass m K ∗ in dense baryonic matter is calculated based on PCAC, current algebra and the Weinberg smoothness hypothesis. The off-shell behavior of the K N scattering amplitudes is treated consistently with PCAC, and the effects of the subthreshold K N resonances are also included. The m K ∗ is foundd to depend crucially on the K N sigma term, Σ KN . Since the current estimates of Σ KN are very uncertain, we discuss various scenarios treating Σ KN as an input parameter; for certain values of Σ KN a collective mode of a hyperon-particle-nucleon-hole state appears at high densities, possibly leading to kaon condensation.

The dark matter distribution of M87 and NGC 1399

Recent X-ray observations of clusters of galaxies indicate that, outside the innermost about 100 kpc region, the ratio of dark matter density to baryonic matter density declines with radius. We show that this result is consistent with a cold dark matter simulation, suggesting the presence of dissipationless dark matter in the observed clusters. This is contrary to previous suggestions that dissipational baryonic dark matter is required to explain the decline in the density ratio. The simulation further shows that, in the inner 100 kpc region, the density ratio should rise with radius. We confirm this property in M87 and NGC 1399, which are close enough to allow the determination of the density ratio in the required inner region. X-ray mappings of the dark matter distribution in clusters of galaxies are therefore consistent with the presence of dissipationless dark matter.

Chiral theory of mesons in dense baryonic matter (II): Meson propagation

We present the results of meson time-like modes in a dense baryonic medium. The model used is the Nambu-Jona-Lasinio model extended to include vector mesons. We find results for the π-, σ-, ω- and a 1-meson time-like modes. We use the same extrapolation technique we have already used to avoid the impossibility of putting heavy mesons on-shell. Vector-meson modes split into a longitudinal and a transverse mode. The σ-mode mixes with the longitudinal ω-mode.

The coupling of quark and gluon condensates in dense systems

Two lagrangians, which implement the QCD scale anomaly, are used to study the coupling of quark and gluon condensates in dense baryonic matter. We show both numerically and analytically that the behaviour of the system depends crucially on the assumed value of the vacuum quark condensate. For a low value, compatible with the bag constant, the gluon condensate “feels” the chiral phase transition. With a higher value, deduced from QCD sum rules, the gluon condensate decouples from the quark condensate and does not change appreciably across the chiral phase transition. In one of the lagrangians, the pion mass drops gradually to zero as the phase transition is approached.

Single explanation for both baryon and dark matter densities.

It is shown that in a general class of models in which the baryon number of the Universe is created by electroweak anomalies, the energy density in dark matter may be related to the energy density in baryons as ${\mathrm{\ensuremath{\Omega}}}_{\mathit{b}}$/${\mathrm{\ensuremath{\Omega}}}_{\mathrm{dm}}$=c times )(proton mass)/(weak scale), where the number c is order unity and calculable from the anomaly equation. The scenario unambiguously predicts charged and neutral particles with weak-scale masses which carry a new conserved quantum number and can be pair produced via the weak interactions.

Chiral theory of mesons in dense baryonic matter (I)

Chiral symmetry restoration at finite baryonic density is studied in a quark model involving both scalar and vector interactions. The presence of vector interactions makes the vacuum stiffer against chiral symmetry restoration. On-shell masses and coupling constants are calculated for the π, ω, ϱ and a 1 mesons. An attempt is made to relate the quark-meson interactions to the observed nucleon-meson coupling constants.

Radiation-induced reversal of baryonic perturbations

view Abstract Citations (1) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radiation-induced Reversal of Baryonic Perturbations Zurek, W. H. Abstract In the context of the cold dark matter (CDM) cosmology it is natural to assume that the first generation of luminous objects formed at redshifts 30 <~ z <~ 100. On galactic scales, their distribution and, therefore, the distribution of luminosity was presumably approximately given by a "biased" density field. If the luminous input of these objects was significant (a fraction of the energetic content of the microwave background), radiative push could have moved the bulk of the baryons into the minima of the dark matter distribution, thus creating baryon-rich seeds for the structure on galactic and larger scales. Moreover, on the scales on which such reversal of baryonic perturbations happens, power in the combined (baryons + dark matter) spectrum of density perturbations would be smaller than in the CDM universe with the same normalization on the very large scales which are opaque and, therefore, immune to the effects of radiation. This suggests "destructive interference" between baryonic and dark matter density perturbations on galactic scales as an explanation for the apparent excess of power observed on the "great attractor" scales, when extrapolated from the estimates of the galaxy-galaxy correlations. Infrared background measurements by COBE should be able to verify-or rule out-this scenario, which, if correct, could also help reconcile the dynamically observed fl with the flatness of the universe favored by inflation. Publication: The Astrophysical Journal Pub Date: April 1991 DOI: 10.1086/169833 Bibcode: 1991ApJ...370..474Z Keywords: Baryons; Cosmic Rays; Dark Matter; Radiation Effects; Astronomical Models; Brightness Distribution; Cosmology; Transfer Functions; Astrophysics; COSMOLOGY; DARK MATTER full text sources ADS |