Multi-Throat Brane Inflation

We present a scenario where brane inflation arises more generically. We start with D3 and anti-D3-branes at the infrared ends of two different throats. This setup is a natural consequence of the assumption that in the beginning we have a multi-throat string compactification with many wandering anti-D3-branes. A long period of inflation is triggered when D3-branes slowly exit the highly warped infrared region, under a potential generically arising from the moduli stabilization. In this scenario, the usual slow-roll conditions are not required, and a large warping is allowed to incorporate the Randall-Sundrum model.Comment: 11 pages; v3: minor revision, PRD versio

Characteristics of Helicopter Accidents Involving Male and Female Pilots

Studies examining aviation accidents have not found differences in accident rates by gender, though there may be gender differences in the types of accident. Baker, Lamb, Grabowski, and Rebok (2001) examined fixed-wing aviation accident rates of male and female private pilots and found that males were more likely to have accidents related to inattention or poor planning while female pilots were more likely to have accidents due to mishandling the aircraft. This research analyzed the National Transportation Safety Board’s aviation accident database system to examine the severity of injury and aircraft damage in rotary-wing (helicopter) accidents by gender. The data indicated that female helicopter pilots have slightly higher accident rates with higher aircraft damage and personnel injury rates at lower levels of training and experience, but have superior records as compared to male pilots at higher levels of experience. Overall, minimal differences in accident rates for helicopter pilots can be tied to gender differences

Cosmological Rescaling through Warped Space

We discuss a scenario where at least part of the homogeneity on a brane world can be directly related to the hierarchy problem through warped space. We study the dynamics of an anti-D3-brane moving toward the infrared cut-off of a warped background. After a region described by the DBI action, the self-energy of the anti-D3-brane will dominate over the background. Then the world-volume scale of the anti-D3-brane is no longer comoving with the background geometry. After it settles down in the infrared end, the world-volume inhomogeneity will appear, to a Poincare observer, to be stretched by an exponentially large ratio. This ratio is close to that of the hierarchy problem between the gravitational and electroweak scales.Comment: 12 pages, 2 figures; v2, PRD version, comments and references adde

Age Differences in Helicopter Accidents: A Preliminary Investigation

This study utilized the NTSB database from 2006 to 2016 to examine differences in severity of accidents by age for helicopter operations. There were 1023 cases included in the data (97.1% male and 2.9% female). The average age for helicopter pilots in the database was 47.00 years (SD=13.78). The average number of flying hours was 5447.98 (SD=6825.90, sk=1.982). An ANOVA was used to examine the effects of age on damage to the aircraft and injury to aircraft occupants. There was not a significant difference in pilot ages across the damage categories of none, minor, substantial, and destroyed, F(3,1019)=.763, p=.515, with average ages of 46.64, 46.04, 46.86, and 49.58 across the categories. There was a significant difference in age across injury categories of none, minor, serious, and fatal, F(3,1019)=7.549, p To examine further the apparent conundrum that injuries went up with age while damage did not, additional analyses were conducted looking particularly at helicopter pilots between 50 and 59 and 60 and 69. For the two groups, there was not a significant difference by age for damage or injury [F(3,234)=.784, p=.504; F(3,234)=.745, p=.526, F(3, 1880=1.395, p=.246, F(3, 188)=.173, p=.915 respectively]. Discounting reporting anomalies, when proportional damage was examined (for age \u3e60 pilots) 86.45% of aircraft sustained substantial damage; in the same age group, 95.31% of aircraft sustained substantial damage or destroyed resulting in 35.42% of those accidents involving serious injury or loss of life

Inflation in Realistic D-Brane Models

We find successful models of D-brane/anti-brane inflation within a string context. We work within the GKP-KKLT class of type IIB string vacua for which many moduli are stabilized through fluxes, as recently modified to include `realistic' orbifold sectors containing standard-model type particles. We allow all moduli to roll when searching for inflationary solutions and find that inflation is not generic inasmuch as special choices must be made for the parameters describing the vacuum. But given these choices inflation can occur for a reasonably wide range of initial conditions for the brane and antibrane. We find that D-terms associated with the orbifold blowing-up modes play an important role in the inflationary dynamics. Since the models contain a standard-model-like sector after inflation, they open up the possibility of addressing reheating issues. We calculate predictions for the CMB temperature fluctuations and find that these can be consistent with observations, but are generically not deep within the scale-invariant regime and so can allow appreciable values for $dn_s/d\ln k$ as well as predicting a potentially observable gravity-wave signal. It is also possible to generate some admixture of isocurvature fluctuations.Comment: 39 pages, 21 figures; added references; identified parameters combining successful inflation with strong warping, as needed for consistency of the approximation

Low energy effective action on a self-gravitating D-brane

Recently the study of braneworld on the self-gravitating D-brane has been initiated and derived the gravitational equation on the brane by holographic and geometrical projection methods. Surprisingly, in common with these two methods, the matter on the brane cannot be the source of the gravity on the brane at leading order. In this paper we will propose the low energy effective action on the D-brane coupled with gravity which derives the same results.Comment: 8 pages, minor corrections, accepted for publication in Physical Review

Braneworld inflation

We discuss various realizations of the four dimensional braneworld inflation in warped geometries of string theory. In all models the inflaton field is represented by a Dp probe brane scalar specifying its position in the warped throat of the compactification manifold. We study existing inflationary throat local geometries, and construct a new example. The inflationary brane is either a D3- or a D5-brane of type IIB string theory. In the latter case the inflationary brane is wrapping a two-cycle of the compactification manifold. We discuss some phenomenological aspects of the model where slow-roll conditions are under computational control.Comment: 31 pages + 6 figures, v2: published PRD versio

On Brane Inflation With Volume Stabilization

The distance between BPS branes in string theory corresponds to a flat direction in the effective potential. Small deviations from supersymmetry may lead to a small uplifting of this flat direction and to brane inflation. However, this scenario can work only if the BPS properties of the branes and the corresponding flatness of the inflaton potential are preserved in the theories with the stable volume compactification. We present an ``inflaton trench'' mechanism that keeps the inflaton potential flat due to shift symmetry, which is related to near BPS symmetry in our model.Comment: 12 pages, 2 figure

On the Moduli Space of the Cascading SU(M+p)xSU(p) Gauge Theory

We carry out a thorough analysis of the moduli space of the cascading gauge theory found on p D3-branes and M wrapped D5-branes at the tip of the conifold. We find various mesonic branches of the moduli space whose string duals involve the warped deformed conifold with different numbers of mobile D3-branes. The branes that are not mobile form a BPS bound state at threshold. In the special case where p is divisible by M there also exists a one-dimensional baryonic branch whose family of supergravity duals, the resolved warped deformed conifolds, was constructed recently. The warped deformed conifold is a special case of these backgrounds where the resolution parameter vanishes and a Z_2 symmetry is restored. We study various brane probes on the resolved warped deformed conifolds, and successfully match the results with the gauge theory. In particular, we show that the radial potential for a D3-brane on this space varies slowly, suggesting a new model of D-brane inflation.Comment: 55 pages, 8 figures; v2: minor corrections; v3: added comments in section 1

Nonsupersymmetric brane vacua in stabilized compactifications

We derive the equations for the nonsupersymmetric vacua of D3-branes in the presence of nonperturbative moduli stabilization in type IIB flux compactifications, and solve and analyze them in the case of two particular 7-brane embeddings at the bottom of the warped deformed conifold. In the limit of large volume and long throat, we obtain vacua by imposing a constraint on the 7-brane embedding. These vacua fill out continuous spaces of higher dimension than the corresponding supersymmetric vacua, and have negative effective cosmological constant. Perturbative stability of these vacua is possible but not generic. Finally, we argue that anti-D3-branes at the tip of the conifold share the same vacua as D3-branes.Comment: 17 pages, 1 figure, LaTeX. v2: references added, typo fixed. v3: version appearing in JHE