2,778 research outputs found

    Legislation for business: is it fit for public consumption?

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    ‘We are convinced that a central problem of the legislative process is that far too many bills are introduced into Parliament in a state that is recognised — even,we suspect, by Ministers — to be less than perfect.’ In short, ‘... bills are too often introduced to Parliament \'half-baked\' and with a lot of the detail insufficiently thought out ...’. I would not mind were Parliament a competent cook, able to complete a process started by government. Were that so, our elected representatives would enhance the democratic process by the part they played in turning out the final product. But the heat of parliamentary debate is rarely sufficient: what enters Parliament half-baked usually emerges half-baked, or worse. ‘The weight and extent of the criticisms received is perhaps the most notable feature of our enquiry.’ Criticism of legislation is as old as legislation itself. King Edward the Sixth wished that ‘the superfluous and tedious statutes were brought into one sum together, and made more plain and short, to the intent that men might better understand them’. But ‘half-baked’ does not just refer to a failure to achieve simplicity or clarity in legislation; it refers to the failure of legislation to achieve its purpose of converting the aims and objectives of government policy into practical rules to regulate our lives in a sophisticated society.

    Budgetary reform: the impact of a December Budget on the Finance Bill and the development of tax legislation

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    This paper considers the Government’s proposals for reforming the budgetary process from the perspective of its impact on the Finance Bill and the development of tax legislation. The paper is divided into three parts. First, it summarises briefly what the White Paper has to say on the subject of the Budget tax proposals, the Finance Bill and tax administration. Thereafter, it considers the implications that a change to a December Budget will have on the Finance Bill process. Finally, the paper looks at possible ways of reforming the system by which tax legislation is developed and enacted.

    Three-Dimensional Simulations of Magnetized Thin Accretion Disks around Black Holes: Stress in the Plunging Region

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    We describe three-dimensional general relativistic magnetohydrodynamic simulations of a geometrically thin accretion disk around a non-spinning black hole. The disk has a thickness h/r0.050.1h/r\sim0.05-0.1 over the radial range (220)GM/c2(2-20)GM/c^2. In steady state, the specific angular momentum profile of the inflowing magnetized gas deviates by less than 2% from that of the standard thin disk model of Novikov & Thorne (1973). Also, the magnetic torque at the radius of the innermost stable circular orbit (ISCO) is only 2\sim2% of the inward flux of angular momentum at this radius. Both results indicate that magnetic coupling across the ISCO is relatively unimportant for geometrically thin disks.Comment: 4 pages, 4 figures, ApJL accepte

    Can Nonlinear Hydromagnetic Waves Support a Self-Gravitating Cloud?

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    Using self-consistent magnetohydrodynamic (MHD) simulations, we explore the hypothesis that nonlinear MHD waves dominate the internal dynamics of galactic molecular clouds. We employ an isothermal equation of state and allow for self-gravity. We adopt ``slab-symmetry,'' which permits motions v\bf v_\perp and fields B\bf B_\perp perpendicular to the mean field, but permits gradients only parallel to the mean field. The Alfv\'en speed vAv_A exceeds the sound speed csc_s by a factor 3303-30. We simulate the free decay of a spectrum of Alfv\'en waves, with and without self-gravity. We also perform simulations with and without self-gravity that include small-scale stochastic forcing. Our major results are as follows: (1) We confirm that fluctuating transverse fields inhibit the mean-field collapse of clouds when the energy in Alfv\'en- like disturbances remains comparable to the cloud's gravitational binding energy. (2) We characterize the turbulent energy spectrum and density structure in magnetically-dominated clouds. The spectra evolve to approximately v,k2B,k2/4πρksv_{\perp,\,k}^2\approx B_{\perp,\,k}^2/4\pi\rho\propto k^{-s} with s2s\sim 2, i.e. approximately consistent with a ``linewidth-size'' relation σv(R)R1/2\sigma_v(R) \propto R^{1/2}. The simulations show large density contrasts, with high density regions confined in part by the fluctuating magnetic fields. (3) We evaluate the input power required to offset dissipation through shocks, as a function of cs/vAc_s/v_A, the velocity dispersion σv\sigma_v, and the scale λ\lambda of the forcing. In equilibrium, the volume dissipation rate is 5.5(cs/va)1/2(λ/L)1/2×ρσv3/L5.5(c_s/v_a)^{1/2} (\lambda/L)^{-1/2}\times \rho \sigma_v^3/L, for a cloud of linear size LL and density ρ\rho. (4) Somewhat speculatively, we apply our results to a ``typical'' molecular cloud. The mechanical power input requiredComment: Accepted for publication in Ap.J. 47 pages, 13 postscript figures. Report also available at http://cfa-www.harvard.edu/~gammie/MHD.p

    Dependence of inner accretion disk stress on parameters: the Schwarzschild case

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    We explore the parameter dependence of inner disk stress in black hole accretion by contrasting the results of a number of simulations, all employing 3-d general relativistic MHD in a Schwarzschild spacetime. Five of these simulations were performed with the intrinsically conservative code HARM3D, which allows careful regulation of the disk aspect ratio, H/R; our simulations span a range in H/R from 0.06 to 0.17. We contrast these simulations with two previously reported simulations in a Schwarzschild spacetime in order to investigate possible dependence of the inner disk stress on magnetic topology. In all cases, much care was devoted to technical issues: ensuring adequate resolution and azimuthal extent, and averaging only over those time-periods when the accretion flow is in approximate inflow equilibrium. We find that the time-averaged radial-dependence of fluid-frame electromagnetic stress is almost completely independent of both disk thickness and poloidal magnetic topology. It rises smoothly inward at all radii (exhibiting no feature associated with the ISCO) until just outside the event horizon, where the stress plummets to zero. Reynolds stress can also be significant near the ISCO and in the plunging region; the magnitude of this stress, however, depends on both disk thickness and magnetic topology. The two stresses combine to make the net angular momentum accreted per unit rest-mass 7-15% less than the angular momentum of the ISCO.Comment: Accepted for publication in ApJ, 52 pages, 38 figures, AASTEX. High-resolution versions can be found at the following links: http://ccrg.rit.edu/~scn/papers/schwarzstress.ps, http://ccrg.rit.edu/~scn/papers/schwarzstress.pd