Chromomagnetic instability in two-flavor quark matter at nonzero temperature

We calculate the effective potential of the 2SC/g2SC phases including vector condensates ($$and$$) and study the gluonic phase and the single plane-wave Larkin-Ovchinnikov-Fulde-Ferrell state at nonzero temperature. Our analysis is performed within the framework of the gauged Nambu--Jona-Lasinio model. We compute potential curvatures with respect to the vector condensates and investigate the temperature dependence of the Meissner masses squared of gluons of color 4--7 and 8 in the neutral 2SC/g2SC phases. The phase diagram is presented in the plane of temperature and coupling strength. The unstable regions for gluons 4--7 and 8 are mapped out on the phase diagram. We find that, apart from the case of strong coupling, the 2SC/g2SC phases at low temperatures are unstable against the vector condensation until the temperature reaches tens of MeV.Comment: 10 pages, 10 figures, revisions to text, published in Phys. Rev.

Analytical and numerical evaluation of the Debye and Meissner masses in dense neutral three-flavor quark matter

We calculate the Debye and Meissner masses and investigate chromomagnetic instability associated with the gapless color superconducting phase changing the strange quark mass $M_s$ and the temperature $T$. Based on the analytical study, we develop a computational procedure to derive the screening masses numerically from curvatures of the thermodynamic potential. When the temperature is zero, from our numerical results for the Meissner masses, we find that instability occurs for $A_1$ and $A_2$ gluons entirely in the gapless color-flavor locked (gCFL) phase, while the Meissner masses are real for $A_4$, $A_5$, $A_6$, and $A_7$ until $M_s$ exceeds a certain value that is larger than the gCFL onset. We then handle mixing between color-diagonal gluons $A_3$, $A_8$, and photon $A_\gamma$, and clarify that, among three eigenvalues of the mass squared matrix, one remains positive, one is always zero because of an unbroken U(1)_\tilde{Q} symmetry, and one exhibits chromomagnetic instability in the gCFL region. We also examine the temperature effects that bring modifications into the Meissner masses. The instability found at large $M_s$ for $A_4$, $A_5$, $A_6$, and $A_7$ persists at finite $T$ into the $u$-quark color superconducting (uSC) phase which has $u$-$d$ and $s$-$u$ but no $d$-$s$ quark pairing and also into the two-flavor color superconducting (2SC) phase characterized by $u$-$d$ quark pairing only. The $A_1$ and $A_2$ instability also goes into the uSC phase, but the 2SC phase has no instability for $A_1$, $A_2$, and $A_3$. We map the unstable region for each gluon onto the phase diagram as a function of $M_s$ and $T$.Comment: 17 pages, 18 figure

Ballistic behavior of boron carbide reinforced AA7075 aluminium alloy using friction stir processing – An experimental study and analytical approach

AbstractHigh strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Among these alloys, magnesium is self explosive and titanium is costlier, and aluminium is most likely to replace steels. Application of aluminium or its alloys is also thought of as an appropriate replacement in defence field, especially to enhance the easiness in mobility of combat vehicles while maintaining the same standard as that of conventional armour grade steels. Hence most of the investigations have been confined to aluminium or its alloys as base material and open an era of developing the newer composite materials to address the major limitation, i.e. tribological properties. The surface composites can be fabricated by incorporating the ceramic carbides like silicon carbide, carbides of transition metals and oxides of aluminium using surface modification techniques, such as high energy laser melt treatment, high energy electron beam irradiation and thermal spray process which are based on fusion route. These techniques yield the fusion related problems, such as interfacial reaction, pin holes, shrinkage cavities or voids and other casting related defects, and pave the way to need of an efficient technique which must be based on solid state. Recently developed friction stir processing technique was used in the present investigation for surface modification of AA7075 aluminum alloy, which is an alternative to steels. In the present investigation, 160 μm sized boron carbide powder was procured and was reduced to 60 μm and 30 μm using high energy ball mill. Subsequently these powders were used to fabricate the surface composites using friction stir processing.Ballistic performance testing as per the military standard (JIS.0108.01) was carried out. In the present work, an analytical method of predicting the ballistic behavior of surface composites was developed. This method was based on energy balance, i.e., the initial energy of impact is same as that of energy absorbed by multi layers. An attempt also has been made to validate the analytical results with the experimental findings. Variation between the analytical and experimental results may be accounted due to the assumptions considering such as isotropic behavior of target and shearing area of contact as cylindrical instead of conical interface As the analytical model yields the ballistic performance in the closer proximity of experimentally obtained, it can be considered to be an approximation to evaluate the ballistic performance of targets

Collective excitations, instabilities, and ground state in dense quark matter

We study the spectrum of light plasmons in the (gapped and gapless) two-flavor color superconducting phases and its connection with the chromomagnetic instabilities and the structure of the ground state. It is revealed that the chromomagnetic instabilities in the 4-7th and 8th gluonic channels correspond to two very different plasmon spectra. These spectra lead us to the unequivocal conclusion about the existence of gluonic condensates (some of which can be spatially inhomogeneous) in the ground state. We also argue that spatially inhomogeneous gluonic condensates should exist in the three-flavor quark matter with the values of the mass of strange quark corresponding to the gapless color-flavor locked state.Comment: Revtex, 5 pages, 4 figures, two figures and clarifications added, to appear in PRD (Rapid Communications

Neutral Larkin--Ovchinnikov--Fulde--Ferrell state and chromomagnetic instability in two-flavor dense QCD

In two-flavor dense quark matter, we describe the dynamics in the single plane wave Larkin--Ovchinnikov--Fulde--Ferrell (LOFF) state satisfying the color and electric neutrality conditions. We find that because the neutral LOFF state itself suffers from a chromomagnetic instability in the whole region where it coexists with the (gapped/gapless) two-flavor superconducting (2SC/g2SC) phases, it cannot cure this instability in those phases. This is unlike the recently revealed gluonic phase which seems to be able to resolve this problem.Comment: Revtex4, 5 pages, 3 figures, clarifications added, to appear in Phys.Rev.Let

Relationships between carbon isotopic composition and mode of binding of natural organic matter in selected marine sediments

Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Organic Geochemistry 38 (2007):1824-1837, doi:10.1016/j.orggeochem.2007.07.008.We have investigated the relationships between radiocarbon (14C) and stable carbon (13C) isotopic composition and the different modes of binding of organic matter (OM) present in surficial sediments from near-shore and continental margin sites that vary in terms of input and depositional conditions. To improve our understanding of the entire OM pool, isotopic analysis of sedimentary sub-fractions, as opposed to individual compounds, was performed. This was achieved by sequentially treating sediments by solvent extraction to examine unbound compounds, followed by saponification to cleave ester linked moieties. Isotopic analysis was then performed on the bulk sediment and resulting residues. The molecular composition of the extracts was examined using gas chromatography/mass spectrometry (GC/MS), and the relative contributions of terrestrial and marine biomarkers were assessed. Radiocarbon abundances (Δ14C) of the bulk sediment reflect a mixture of modern, pre-aged and fossil carbon. Offsets in Δ14C between the bulk sediment and sediment residues demonstrate varying associations of these carbon pools. For the majority of sites, a negative offset between extracted (EX2 RES) and saponified (SA-RES) sediment 1 residues results from the removal of relatively 4C-rich material during saponification. Saponification extracts (SAEs) are mainly composed of short chain (n-C12 to n-C24) alkanoic acids with an even/odd dominance indicating a predominantly marine algal or microbial source. This provides evidence for the protection of labile marine carbon by chemical binding. This study aims to bridge the gap between molecular level and bulk OM analyses in marine sediments.The work was supported by funds from the National Science Foundation (CHE-0089172; OCE-0526268)

Color-flavor locked superconductor in a magnetic field

We study the effects of moderately strong magnetic fields on the properties of color-flavor locked color superconducting quark matter in the framework of the Nambu-Jona-Lasinio model. We find that the energy gaps, which describe the color superconducting pairing as well as the magnetization, are oscillating functions of the magnetic field. Also, we observe that the oscillations of the magnetization can be so strong that homogeneous quark matter becomes metastable for a range of parameters. We suggest that this points to the possibility of magnetic domains or other types of magnetic inhomogeneities in the quark cores of magnetars.Comment: 12 pages, 3 figures. Version accepted for publication in Phys. Rev.

New Method to Harness More Wind Energy

A new and novel method to harness more wind energy has been designed Details of the experimental results and theoretical explanation is presented in the paper. The simplicity and economic viability of the method is expected to be a boon in converting poor windy sites to usable ones and to harness more energy at the existing windmill sites