16,314 research outputs found
Testing M(atrix)-Theory at Two Loops
I discuss the relation between M-theory and M(atrix)-theory in flat space by
considering the effective potential for the scattering of two groups of
D0-branes in both theories. An explicit calculation of this potential up to two
loop order in M(atrix)-theory reveals a fascinating agreement. Lecture given at
Strings '97; June 17, 1997.Comment: 7 pages, latex, 1 figure. Lecture given at STRINGS9
A Two-Loop Test of M(atrix) Theory
We consider the scattering of two Dirichlet zero-branes in M(atrix) theory.
Using the formulation of M(atrix) theory in terms of ten-dimensional super
Yang-Mills theory dimensionally reduced to -dimensions, we obtain the
effective (velocity dependent) potential describing these particles. At
one-loop we obtain the well known result for the leading order of the effective
potential , where and are the relative velocity
and distance between the two zero-branes respectively. A calculation of the
effective potential at two-loops shows that no renormalizations of the
-term of the effective potential occur at this order.Comment: 17 pages, tex, 1 figure, a few misprints corrected. Version to appear
in Nuclear Physics
General covariance of the non-abelian DBI-action: Checks and Balances
We perform three tests on our proposal to implement diffeomorphism invariance
in the non-abelian D0-brane DBI action as a basepoint independence constraint
between matrix Riemann normal coordinate systems. First we show that T-duality
along an isometry correctly interchanges the potential and kinetic terms in the
action. Second, we show that the method to impose basepoint independence using
an auxiliary dN^2-dimensional non-linear sigma model also works for metrics
which are curved along the brane, provided a physical gauge choice is made at
the end. Third, we show that without alteration this method is applicable to
higher order in velocities. Testing specifically to order four, we elucidate
the range of validity of the symmetrized trace approximation to the non-abelian
DBI action.Comment: LaTeX, 22 page
The spin periods of magnetic cataclysmic variables
We have used a model of magnetic accretion to investigate the rotational equilibria of magnetic cataclysmic variables (mCVs). This has enabled us toderive a set of equilibrium spin periods as a function of orbital period and magnetic moment which we use to estimate the magnetic moments of all known intermediate polars. We further show how these equilibrium spin periods relate to the polar synchronisation condition and use these results to calculate the theoretical histogram describing the distribution of magnetic CVs as a function of P_spin / P_orb. We demonstrate that this is in remarkable agreement with the observed distribution assuming that the number of systems as a function of white dwarf magnetic moment is distributed according to N(mu_1) ~ mu_1^-2
Elastic Form Factors of He up to Large
Elastic electron scattering off He and He has recently been studied
at forward and backward scattering angles in Hall A at JLab. The results will
provide accurate data on the elastic form factors, charge and magnetic for
He and charge only for He, up to squared momentum transfer -values
of 3.2 GeV.Comment: 3 pages, Proceedings of EFB2
The three-loop beta-fuction of QCD with the clover action
We calculate, to 3 loops in perturbation theory, the bare -function of
QCD, formulated on the lattice with the clover fermionic action. The dependence
of our result on the number of colors , the number of fermionic flavors
, as well as the clover parameter , is shown explicitly.
A direct outcome of our calculation is the two-loop relation between the bare
coupling constant and the one renormalized in the MS-bar scheme.
Further, we can immediately derive the three-loop correction to the relation
between the lattice -parameter and , which is important in checks
of asymptotic scaling. For typical values of , this correction is found
to be very pronounced.Comment: 14 pages, 2 eps figure
Do exchange rates have any impact upon UK inward foreign direct investment?
This paper examines the impact of the level and volatility of the real exchange rate on UK foreign direct investment (FDI) inflows from the seven major countries of origin of the investment over the period 1975 to 2001. We use both fixed effects and dynamic generalised methods of moments (GMM) panel estimation techniques, and manufacturing data disaggregated by high and low R&D content of the sector of destination. Our results provide strong evidence that exchange rate volatility has a negative impact on FDI flows into the UK, irrespective of the sector of destination of the investment. On the other hand, the level of the real exchange rate is found to have a statistically insignificant effect on FDI after controlling for endogeneity of the regressors
Kinematic model inversions of hot star recurrent DAC data - tests against dynamical CIR models
The Discrete Absorption Components (DACs) commonly observed in the ultraviolet lines of hot stars have previously been modelled by dynamical simulations of Corotating Interaction Regions (CIRs) in their fine-driven stellar winds. Here we apply the kinematic DAC inversion method of Brown et al. to the hydrodynamical CIR models and test the reliability of the results obtained. We conclude that the inversion method is able to recover valuable information on the velocity structure of the mean wind and to trace movement of velocity plateaux in the hydrodynamical data, though the recovered density profile of the stream is correct only very near to the stellar surface
Final state interactions in the electroweak nuclear response
I review the description of the electroweak nuclear response at large
momentum transfer within nonrelativistic many-body theory. Special
consideration is given to the effects of final state interactions, which are
known to be large in both inclusive and semi-inclusive processes. The results
of theoretical calculations of electron-nucleus scattering observables are
compared to the data, and the generalization to charged current
neutrino-nucleus interactions is discussed.Comment: Invited talk at NUINT05. To be published in Nucl. Phys. B Proceedings
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