Stability Constraints on Classical de Sitter Vacua

We present further no-go theorems for classical de Sitter vacua in Type II string theory, i.e., de Sitter constructions that do not invoke non-perturbative effects or explicit supersymmetry breaking localized sources. By analyzing the stability of the 4D potential arising from compactification on manfiolds with curvature, fluxes, and orientifold planes, we found that additional ingredients, beyond the minimal ones presented so far, are necessary to avoid the presence of unstable modes. We enumerate the minimal setups for (meta)stable de Sitter vacua to arise in this context.Comment: 18 pages; v2: argument improved, references adde

Radiocarbon Calibration for Japanese Wood Samples

The radiocarbon content of Japanese cedars was measured by accelerator mass spectrometry for decadal tree-ring samples from the period of 240 BC to AD 900. Conventional gas counting was also used for part of the samples. The data were compared with the INTCAL98 calibration curve. The results indicate that the difference in atmospheric 14C between Japan and North America or Europe is negligible at this period, less than 18 14C yr using an average of 50 yr. However, in the period of about AD 100 to about AD 200, we cannot exclude the possibility of a deviation of the order of 30 to 40 14C yr to the older ages.

Imagining, Recognizing and Discriminating: Reconsidering the Ability Hypothesis

According to the Ability Hypothesis, knowing what it is like to have experience E is just having the ability to imagine or recognize or remember having experience E. I examine various versions of the Ability Hypothesis and point out that they all face serious objections. Then I propose a new version that is not vulnerable to these objections: knowing what it is like to experience E is having the ability todiscriminate imagining or having experience E from imagining or having any other experience. I argue that if we replace the ability to imagine or recognize with the ability to discriminate, the Ability Hypothesis can be salvaged