An exterior for the G\"{o}del spacetime

We match the vacuum, stationary, cylindrically symmetric solution of Einstein's field equations with $\Lambda$, in a form recently given by Santos, as an exterior to an infinite cylinder of dust cut out of a G\"{o}del universe. There are three cases, depending on the radius of the cylinder. Closed timelike curves are present in the exteriors of some of the solutions. There is a considerable similarity between the spacetimes investigated here and those of van Stockum referring to an infinite cylinder of rotating dust matched to vacuum, with $\Lambda=0$.Comment: 11 pages, LaTeX 2.09, no figures. Submitted to Classical and Quantum Gravit

Study of the effect of pH, salinity and DOC on fluorescence of synthetic mixtures of freshwater and marine salts

In order to provide support for the discussion of the fate of organic matter in estuaries, a laboratory simulation was performed by changing freshwater ionic strength, pH and organic matter content. The change in spectroscopic characteristics caused by variations in salinity, pH and organic matter concentration in the filtered samples was observed by UV-Vis and fluorescence spectroscopy. The increase in emission fluorescence intensity of dissolved organic matter (DOM) due to increasing salinity (in the range 0 to 5 g l−1) is affected by the pH of the samples. The emission fluorescence intensity at the three maxima observed in the fluorescence spectra, is linearly correlated with dissolved organic carbon (DOC) concentration at several salinity values in the same sample. The increase in organic matter concentration caused a shift in the emission peak wavelength at 410 nm for several salinity values.We concluded that it is necessary to take into account the influence of salinity and pH on emission fluorescence of dissolved organic matter if it is to be used as a tracer in estuarine or near shore areas

Manipulation of the dynamics of many-body systems via quantum control methods

We investigate how dynamical decoupling methods may be used to manipulate the time evolution of quantum many-body systems. These methods consist of sequences of external control operations designed to induce a desired dynamics. The systems considered for the analysis are one-dimensional spin-1/2 models, which, according to the parameters of the Hamiltonian, may be in the integrable or non-integrable limits, and in the gapped or gapless phases. We show that an appropriate control sequence may lead a chaotic chain to evolve as an integrable chain and a system in the gapless phase to behave as a system in the gapped phase. A key ingredient for the control schemes developed here is the possibility to use, in the same sequence, different time intervals between control operations.Comment: 10 pages, 3 figure

Knizhnik-Zamolodchikov-Bernard equations connected with the eight-vertex model

Using quasiclassical limit of Baxter's 8 - vertex R - matrix, an elliptic generalization of the Knizhnik-Zamolodchikov equation is constructed. Via Off-Shell Bethe ansatz an integrable representation for this equation is obtained. It is shown that there exists a gauge transformation connecting this equation with Knizhnik-Zamolodchikov-Bernard equation for SU(2)-WZNW model on torus.Comment: 20 pages latex, macro: tcilate

"The United States and Her Creditors: Can the Symbiosis Last?"

The main arguments in this paper can be simply stated: 1) If output in the US grows fast enough to keep unemployment constant between now and 2010 and if there is no further depreciation in the dollar, the deficit in the balance of trade is likely to get worse, perhaps reaching 7.5 per cent by the end of the decade. 2) If the trade deficit does not improve, let alone if it gets worse, there will be a large further deterioration in the US's net foreign asset position so that, with interest rates rising, net income payments from abroad will at last turn negative and the deficit in the current account as a whole could reach at least 8.5 per cent of GDP. . . .

"Deficits, Debts and Growth: A Reprieve but not a Pardon"

These are fast moving times. Two years ago, the U.S. Congressional Budget Office (CBO, 2001) projected a federal budget surplus of $172 billion for fiscal year 2003. One year ago, the projected figure had changed to a deficit of$145 billion (CBO 2002). The actual figure, near the end of fiscal year 2003, turned out to be a deficit of about $390 billion. And just one month ago, President Bush submitted a request to Congress for an additional$87 billion appropriation for war expenditures, over and above the $166 billion tallied so far. It is widely anticipated that even this will have to be revised upward by the end of the coming year (Stevenson 2003; Firestone 2003).

"Is Deficit-Financed Growth Limited? Policies and Prospects in An Election Year"

Wynne Godley, our Levy Institute colleague, has warned since 1999 that the falling personal saving and rising borrowing trends that had powered the US economic expansion were not sustainable. He also warned that when these trends were reversed, as has happened in other countries, the expansion would come to a halt unless there were major changes in fiscal policy. Not long ago, official circles insisted that monetary policy was the most desirable tool, and that fiscal deficits were not only unnecessary but also harmful(ERP, 2000, p.31-34; Greenspan, 2000). Some economists, notably Edmund Phelps of Columbia University, went so far as to suggest that the economic expansion was not caused by rising demand, but rather because growth had become ÔstructuralÕ (Financial Times, August 9, 2000).