We reexamine large CP-violating phases in the general minimal supersymmetric standard model, as well as more restricted models. We perform a detailed scan over parameter space to find solutions which satisfy the current experimental limits on the electric dipole moments of the electron, neutron and 199 Hg atom, exploring the allowed configurations of phases and masses, and we attempt to quantify the level of tuning of the parameters necessary to populate the regions of cancellations. We then consider the measurement of CP-violating phases at a future linear collider. We find that measurements of chargino and neutralino masses and production cross sections allow for a determination of 1 ͑the phase of M 1 ) to a precision of /30, while the EDM constraints require that be too small to be measured. Using the EDM constraints we find that the CP-even model parameters and the phase 1 can be determined at a linear collider with 400 GeV c.m. energy. As long as some information on the size of ͉͉ is included in the observables, a measurement of 1 is guaranteed for 1 Ͼ/10. To unambiguously identify CP violation, we construct CP-odd kinematical variables at a linear collider. However, the CP asymmetries are rather small, typically about 0.1-1.5 %, and it will be challenging to experimentally observe the predicted asymmetries.

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We examine the cosmology and hierarchy of scales in models with branes immersed in a five-dimensional curved spacetime subject to radion stabilization. When the radion field is time-independent and the inter-brane spacing is stabilized, the universe can naturally find itself in the radiation-dominated epoch. This feature is independent of the form of the stabilizing potential. We recover the standard Friedmann equations without assuming a specific form for the bulk energy-momentum tensor. In the models considered, if the observable brane has positive tension, a solution to the hierarchy problem requires the presence of a negative tension brane somewhere in the bulk. We find that the string scale can be as low as the electroweak scale. In the situation of self-tuning branes where the bulk cosmological constant is set to zero, the brane tensions have hierarchical values. In the case of a polynomial stabilizing potential no new hierarchy is created.Typeset using REVT E X * barger@oriole.physics.wisc.edu, than@pheno.physics.wisc.edu, li@pheno.physics.wisc.edu, lykken@fnal.gov, marfatia@pheno.physics.wisc.edu 1 I. Introduction. It has recently been realized that the string scale can be much lower than the Planck scale and even close to the electroweak scale [1]. A low string scale provides new avenues on solving the hierarchy problem [2,3]. The argument resides in the fact that a low string scale (M X ) may result in the apparent size of the Planck scale (M P l ) due to the existence of a large volume (R n ) of compact extra dimensions,. Such a scenario may lead to a rich phenomenology at low energies and is thus testable at collider experiments [4].Recently, a model involving just one extra dimension with a background AdS 5 metric was proposed by Randall and Sundrum [3] (see also Ref. [5]). In this scenario, two branes (one with positive tension and the other with negative tension) are located at the fixed points of an S 1 /Z 2 orbifold in a bulk with negative cosmological constant. An exponential hierarchy between the physical scales on the two branes is generated due to the curved spacetime, providing an explanation for the large hierarchy between the weak and Planck scales. The model is amenable to a holographic interpretation motivated by string theories [6]. However, the Randall-Sundrum model has some drawbacks. First, a perfect fine-tuning among the brane tensions and the bulk cosmological constant is needed to guarantee a static solution for the warped metric of spacetime. Mechanisms for stabilizing the brane locations via interactions between a bulk scalar field (called the radion) and the branes were suggested in [7] and elaborated in [8], where an elegant solution that accounts for the back-reaction of the scalar profile on the geometry is outlined. An overall fine-tuning equivalent to setting the four-dimensional cosmological constant to zero is still present. Second, it was found that the brane world may not lead to the standard cosmology [9,10]. In particular, the Hubble parameter H was found to...

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