Thermal Renormalons in Scalar Field Theory

In the frame of the scalar theory $g \phi ^{4}$, we explore the occurrence of thermal renormalons, i. e. temperature dependent singularities in the Borel plane. The discussion of a particular renormalon type diagram at finite temperature, using Thermofield Dynamics, allows us to establish that these singularities actually get a temperature dependence. This dependence appears in the residues of the poles, remaining their positions unchanged with temperature.Comment: 12 pages, 3 figures, uses feynMF. Minor correction

Finite Temperature Renormalization of the (ϕ3)6(\phi^3)_6- and (ϕ4)4(\phi^4)_4-Models at Zero Momentum

A self-consistent renormalization scheme at finite temperature and zero momentum is used together with the finite temperature renormalization group to study the temperature dependence of the mass and the coupling to one-loop order in the $(\phi^3)_6$- and $(\phi^4)_4$-models. It is found that the critical temperature is shifted relative to the naive one-loop result and the coupling constants at the critical temperature get large corrections. In the high temperature limit of the \phiff-model the coupling decreases.Comment: 16 pages, plain Latex, NORDITA-92/38

Effects of a New Triple-alpha Reaction on X-ray Bursts of a Helium Accreting Neutron Star

The effects of a new triple-$\alpha$ reaction rate (OKK rate) on the helium flash of a helium accreting neutron star in a binary system have been investigated. Since the ignition points determine the properties of a thermonuclear flash of type I X-ray bursts, we examine the cases of different accretion rates, $dM/dt (\dot{M})$, of helium from $3\times10^{-10} M_{\odot} \rm yr^{-1}$ to $3\times10^{-8} M_{\odot} \rm yr^{-1}$, which could cover the observed accretion rates. We find that for the cases of low accretion rates, nuclear burnings are ignited at the helium layers of rather low densities. As a consequence, helium deflagration would be triggered for all cases of lower accretion rate than $\dot{M}\simeq 3\times10^{-8} M_{\odot} \rm yr^{-1}$. We find that OKK rate could be barely consistent with the available observations of the X-ray bursts on the helium accreting neutron star. However this coincidence is found to depend on the properties of crustal heating and the neutron star model.We suggest that OKK rate would be reduced by a factor of $10^{2-3}$ for $10^8$ K in the range of the observational errors.Comment: 10 pages, 4 figure

Inclusive leadership: Toward reshaping corporate purpose for sustainable development

This paper delves into the complex relationship between business leadership, sustainability, and inclusivity, representing a step towards developing a more inclusive leadership approach to sustainable development that fosters shared power relations between business leaders and marginalized members of society. With environmental and social conditions worsening, it is urgent that corporations move away from the neoliberal profit-maximization models advocated by Milton Friedman and instead prioritize humanity and the environment. This requires a fundamental restructuring of businesses to move beyond profit maximization and address societal power imbalances by including all stakeholders. Our inclusive leadership for sustainable development framework, rooted in symbolic interactionism, offers a holistic lens for including marginalized groups. At the microlevel, it focuses on business leaders' personas, characterized by pro-demographic diversity and biodiversity, cognitive complexity for sustainable development, and social empathy, that can potentially create macro-level impact. These characteristics accompanied by macro perspectives that focus on repurposing corporations away from neoliberalism towards sustainability, would be a step forward in cultivating shared power dynamics between business leaders and marginalized communities for the betterment of society

Carbon burning in intermediate mass primordial stars

The evolution of a zero metallicity 9 M_s star is computed, analyzed and compared with that of a solar metallicity star of identical ZAMS mass. Our computations range from the main sequence until the formation of a massive oxygen-neon white dwarf. Special attention has been payed to carbon burning in conditions of partial degeneracy as well as to the subsequent thermally pulsing Super-AGB phase. The latter develops in a fashion very similar to that of a solar metallicity 9 M_s star, as a consequence of the significant enrichment in metals of the stellar envelope that ensues due to the so-called third dredge-up episode. The abundances in mass of the main isotopes in the final ONe core resulting from the evolution are X(^{16}O) approx 0.59, X(^{20}Ne) approx 0.28 and X(^{24}Mg) approx 0.05. This core is surrounded by a 0.05 M_s buffer mainly composed of carbon and oxygen, and on top of it a He envelope of mass 10^{-4} M_sComment: 11 pages, 11 figures, accepted for publication in A&

On the Mott glass in the one-dimensional half-filled charge density waves

We study the effect of impurity pinning on a one-dimensional half-filled electron system, which is expressed in terms of a phase Hamiltonian with the charge degree of freedom. Within the classical treatment, the pinned state is examined numerically. The Mott glass, which has been pointed out by Orignac et al. [Phys. Rev. Lett 83 (1999) 2378], appears in the intermediate region where the impurity potential competes with the commensurate potential. Such a state is verified by calculating the soliton formation energy, the local restoring force around the pinned state and the optical conductivity.Comment: 13 pages, 5 figures, to be published in J. Phys. Soc. Jpn. 72 No.11 (2003

Detection of highly ionized O and Ne absorption lines in the X-ray spectrum of 4U1820-303 in the globular cluster, NGC 6624

We searched for absorption lines of highly ionized O and Ne in the energy spectra of two Low-mass X-ray binaries, 4U1820-303 in the globular cluster NGC6624 and Cyg X-2, observed with the Chandra LETG, and detected O VII, O VIII and Ne IX absorption lines for 4U1820-303. The equivalent width of the O VII K alpha line was 1.19 +0.47/-0.30 eV (90 % errors) and the significance was 6.5 sigma. Absorption lines were not detected for Cyg X-2 with a 90 % upper limit on the equivalent width of 1.06 eV for O VII K alpha. The absorption lines observed in 4U1820-303 are likely due to hot interstellar medium, because O will be fully photo-ionized if the absorbing column is located close to the binary system. The velocity dispersion is restricted to b = 200 - 420 km/s from consistency between O VII K alpha and K beta lines, Ne/O abundance ratio, and H column density. The average temperature and the O VII density are respectively estimated to be log(T[K]) = 6.2 - 6.3 and n(OVII) = (0.7 - 2.3) x 10^{-6} cm^{-3}. The difference of O VII column densities for the two sources may be connected to the enhancement of the soft X-ray background (SXB) towards the Galactic bulge region. Using the polytrope model of hot gas to account for the SXB we corrected for the density gradient and estimated the midplane O VII density at the solar neighborhood. The scale height of hot gas is then estimated using the AGN absorption lines. It is suggested that a significant portion of both the AGN absorption lines and the high-latitude SXB emission lines can be explained by the hot gas in our Galaxy.Comment: Accepted for publication in ApJ. 7 pages, 9 eps figure

Spin fluctuations and superconductivity in noncentrosymmetric heavy fermion systems CeRhSi3_3 and CeIrSi3_3

We study the normal and the superconducting properties in noncentrosymmetric heavy fermion superconductors CeRhSi$_3$ and CeIrSi$_3$. For the normal state, we show that experimentally observed linear temperature dependence of the resistivity is understood through the antiferromagnetic spin fluctuations near the quantum critical point (QCP) in three dimensions. For the superconducting state, we derive a general formula to calculate the upper critical field $H_{c2}$, with which we can treat the Pauli and the orbital depairing effect on an equal footing. The strong coupling effect for general electronic structures is also taken into account. We show that the experimentally observed features in $H_{c2}\parallel \hat{z}$, the huge value up to 30(T), the downward curvatures, and the strong pressure dependence, are naturally understood as an interplay of the Rashba spin-orbit interaction due to the lack of inversion symmetry and the spin fluctuations near the QCP. The large anisotropy between $H_{c2}\parallel \hat{z}$ and $H_{c2}\perp \hat{z}$ is explained in terms of the spin-orbit interaction. Furthermore, a possible realization of the Fulde-Ferrell- Larkin-Ovchinnikov state for $H\perp \hat{z}$ is studied. We also examine effects of spin-flip scattering processes in the pairing interaction and those of the applied magnetic field on the spin fluctuations. We find that the above mentioned results are robust against these effects. The consistency of our results strongly supports the scenario that the superconductivity in CeRhSi$_3$ and CeIrSi$_3$ is mediated by the spin fluctuations near the QCP.Comment: 21pages, 13figures, to be published in Phys. Rev.

Mechanisms for High-frequency QPOs in Neutron Star and Black Hole Binaries

We explain the millisecond variability detected by Rossi X-ray Timing Explorer (RXTE) in the X-ray emission from a number of low mass X-ray binary systems (Sco X-1, 4U1728-34, 4U1608-522, 4U1636-536, 4U0614+091, 4U1735-44, 4U1820-30, GX5-1 and etc) in terms of dynamics of the centrifugal barrier, a hot boundary region surrounding a neutron star. We demonstrate that this region may experience the relaxation oscillations, and that the displacements of a gas element both in radial and vertical directions occur at the same main frequency, of order of the local Keplerian frequency. We show the importance of the effect of a splitting of the main frequency produced by the Coriolis force in a rotating disk for the interpretation of a spacing between the QPO peaks. We estimate a magnitude of the splitting effect and present a simple formula for the whole spectrum of the split frequencies. It is interesting that the first three lowest-order overtones fall in the range of 200-1200 Hz and match the kHz-QPO frequencies observed by RXTE. Similar phenomena should also occur in Black Hole (BH) systems, but, since the QPO frequency is inversely proportional to the mass of a compact object, the frequency of the centrifugal-barrier oscillations in the BH systems should be a factor of 5-10 lower than that for the NS systems. The X-ray spectrum formed in this region is a result of upscattering of a soft radiation (from a disk and a NS surface) off relatively hot electrons in the boundary layer. We also briefly discuss some alternative QPO models, including a possibility of acoustic oscillations in the boundary layer, the proper stellar rotation, and g-mode disk oscillations.Comment: The paper is coming out in the Astrophysical Journal in the 1st of May issue of 199