Contact Lie algebras of vector fields on the plane

The paper is devoted to the complete classification of all real Lie algebras of contact vector fields on the first jet space of one-dimensional submanifolds in the plane. This completes Sophus Lie's classification of all possible Lie algebras of contact symmetries for ordinary differential equations. As a main tool we use the abstract theory of filtered and graded Lie algebras. We also describe all differential and integral invariants of new Lie algebras found in the paper and discuss the infinite-dimensional case.Comment: 20 pages. Published copy, also available at http://www.maths.warwick.ac.uk/gt/GTVol3/paper1.abs.htm

A Response to Cogley and Sbordone's Comment on "Closed-Form Estimates of the New Keynesian Phillips Curve with Time-Varying Trend Inflation"

In their 2010 comment (which we refer to as CS10), Cogley and Sbordone argue that: (i) our estimates are not entirely closed form, and hence are arbitrary; (ii) we cannot guarantee that our estimates are valid, while their estimates (Cogley and Sbordone 2008, henceforth CS08) always are; and (iii) the estimates in CS08, in terms of goodness of fit, are just as good as other, much different estimates in our paper. We show in this reply that the exact closed-form estimates are virtually the same as the "quasi" closed-form estimates. Our estimates are consistent with the implicit assumptions underlying the first-stage VAR used to form expectations, while the estimates in CS08 are not. As a result, the estimates in CS08 point towards model misspecification. We also rebut the goodness of fit comparisons in CS10, and provide a more credible exercise that illustrates that our estimates outperform CS08's estimates.closed form; model-consistent expectations; New Keynesian Phillips curve; forward-looking Euler equation; time-varying trend inflation

Perlindungan Hukum terhadap Bank Atas Konflik Alas Hak dari Hak Tanggungan (Studi Kasus : Putusan Pn Medan Register No.113/pdt.g/2006/pn-mdn Tanggal 01-03-2007)

In Addition to the basic principles as a consequence of the legal protection for the Bank as creditor with collateral right as the quarantee, the legal action taken by the Bank for the dispute of basic occured is a somasi to debtor, a law suit against the debtor through State Court Uitvoer Bij Voorad, the execution of court decision, the execution of debt acknowledgment, execution of collateral right, parate of execution of collateral right, execution against the quarantor, forced-agency institution ang bankruptcy through the Commercial Court. The solution taken by the Bank as the holder of collateral right of the conflicton the basic right functioned as debt quarantee is loan restructuring, facility transfer, and partly or wholly repaymnet of debt. Bank can also fight the State Court back, file a law suit against the plaintiffs, the defendants, National Land Board and the Police who have carried ot the execution of the object served as debt quarantee with a burden of collateral right

Invariants of differential equations defined by vector fields

We determine the most general group of equivalence transformations for a family of differential equations defined by an arbitrary vector field on a manifold. We also find all invariants and differential invariants for this group up to the second order. A result on the characterization of classes of these equations by the invariant functions is also given.Comment: 13 page

Estimation of Forward-Looking Relationships in Closed Form: An Application to the New Keynesian Phillips Curve

We illustrate the importance of placing model-consistent restrictions on expectations in the estimation of forward-looking Euler equations. In two-stage limited-information settings where first-stage estimates are used to proxy for expectations, parameter estimates can differ substantially, depending on whether these restrictions are imposed or not. This is shown in an application to the New Keynesian Phillips Curve (NKPC), first in a Monte Carlo exercise, and then on actual data. The closed-form (CF) estimates require by construction that expectations of inflation be model-consistent at all points in time, while the difference-equation (DE) estimates impose no model discipline on expectations. Between those two polar extremes there is a wide range of alternative DE specifications, based on the same dynamic relationship, that explicitly impose model restrictions on expectations for a finite number of periods. In our application, these last estimates quickly converge to the CF estimates, and illustrate that the DE estimates in Cogley and Sbordone (2008) are not robust to imposing modest model requirements on expectations. In particular, our estimates show that the NKPC is not purely forward-looking, and thus that time-varying trend inflation is insufficient to explain inflation persistence.closed form; model-consistent expectations; New Keynesian Phillips curve; forward- looking Euler equation; time-varying trend inflation

Momentum anisotropies in the quark coalescence model

Based on the quark coalescence model, we derive relations among the momentum anisotropies of mesons and baryons in relativistic heavy ion collisions from a given, but arbitrary azimuthal distribution for the partons. Besides the familiar even Fourier coefficients such as the elliptic flow, we also pay attention to odd Fourier coefficients such as the directed flow, which has been observed at finite rapidity even at RHIC energies.Comment: 5 page

Nucleon-nucleon cross sections in neutron-rich matter and isospin transport in heavy-ion reactions at intermediate energies

Nucleon-nucleon (NN) cross sections are evaluated in neutron-rich matter using a scaling model according to nucleon effective masses. It is found that the in-medium NN cross sections are not only reduced but also have a different isospin dependence compared with the free-space ones. Because of the neutron-proton effective mass splitting the difference between nn and pp scattering cross sections increases with the increasing isospin asymmetry of the medium. Within the transport model IBUU04, the in-medium NN cross sections are found to influence significantly the isospin transport in heavy-ion reactions. With the in-medium NN cross sections, a symmetry energy of $E_{sym}(\rho)\approx 31.6(\rho /\rho_{0})^{0.69}$ was found most acceptable compared with both the MSU isospin diffusion data and the presently acceptable neutron-skin thickness in $^{208}$Pb. The isospin dependent part $K_{asy}(\rho _{0})$ of isobaric nuclear incompressibility was further narrowed down to $-500\pm 50$ MeV. The possibility of determining simultaneously the in-medium NN cross sections and the symmetry energy was also studied. The proton transverse flow, or even better the combined transverse flow of neutrons and protons, can be used as a probe of the in-medium NN cross sections without much hindrance from the uncertainties of the symmetry energy.Comment: 32 pages including 14 figures. Submitted to Phys. Rev.

Determination of the stiffness of the nuclear symmetry energy from isospin diffusion

With an isospin- and momentum-dependent transport model, we find that the degree of isospin diffusion in heavy ion collisions at intermediate energies is affected by both the stiffness of the nuclear symmetry energy and the momentum dependence of the nucleon potential. Using a momentum dependence derived from the Gogny effective interaction, recent experimental data from NSCL/MSU on isospin diffusion are shown to be consistent with a nuclear symmetry energy given by $E_{\text{sym}}(\rho)\approx 31.6(\rho /\rho_{0})^{1.05}$ at subnormal densities. This leads to a significantly constrained value of about -550 MeV for the isospin-dependent part of the isobaric incompressibility of isospin asymmetric nuclear matter.Comment: 4 pages, 4 figures, 1 table, revised version, to appear in PR

Differential isospin-fractionation in dilute asymmetric nuclear matter

The differential isospin-fractionation (IsoF) during the liquid-gas phase transition in dilute asymmetric nuclear matter is studied as a function of nucleon momentum. Within a self-consistent thermal model it is shown that the neutron/proton ratio of the gas phase becomes {\it smaller} than that of the liquid phase for energetic nucleons, although the gas phase is overall more neutron-rich. Clear indications of the differential IsoF consistent with the thermal model predictions are demonstrated within a transport model for heavy-ion reactions. Future comparisons with experimental data will allow us to extract critical information about the momentum dependence of the isovector strong interaction.Comment: Rapid Communication, Phys. Rev. C (2007) in pres

Lie Symmetries and Exact Solutions of First Order Difference Schemes

We show that any first order ordinary differential equation with a known Lie point symmetry group can be discretized into a difference scheme with the same symmetry group. In general, the lattices are not regular ones, but must be adapted to the symmetries considered. The invariant difference schemes can be so chosen that their solutions coincide exactly with those of the original differential equation.Comment: Minor changes and journal-re