arXiv subjects

Tom Rudelius

Publications and source records attributed to Tom Rudelius.

62 records · Page 4Linked to original sources

arXiv2015

Constraints on Axion Inflation from the Weak Gravity Conjecture

We derive constraints facing models of axion inflation based on decay constant alignment from a string-theoretic and quantum gravitational perspective. In particular, we investigate the prospects for alignment and `anti-alignment' of $C_4$ axion decay constants in type IIB string theory, deriving a strict no-go result in the latter case. We discuss the relationship of axion decay constants to the weak gravity conjecture and demonstrate agreement between our string-theoretic constraints and those coming from the `generalized' weak gravity conjecture. Finally, we consider a particular model of decay constant alignment in which the potential of $C_4$ axions in type IIB compactifications on a Calabi-Yau three-fold is dominated by contributions from $D7$-branes, pointing out that this model evades some of the challenges derived earlier in our paper but is highly constrained by other geometric considerations.

hep-th↗

arXiv2015

Geometry of 6D RG Flows

We study renormalization group flows between six-dimensional superconformal field theories (SCFTs) using their geometric realizations as singular limits of F-theory compactified on elliptically fibered Calabi-Yau threefolds. There are two general types of flows: One corresponds to giving expectation values to scalars in the tensor multiplets (tensor branch flow) realized as resolving the base of the geometry. The other corresponds to giving expectation values to hypermultiplets (Higgs branch flow) realized as complex structure deformations of the geometry. To corroborate this physical picture we calculate the change in the anomaly polynomial for these theories, finding strong evidence for a flow from a UV fixed point to an IR fixed point. Moreover, we find evidence against non-trivial dualities for 6D SCFTs. In addition we find non-trivial RG flows for theories realizing small E8 instantons on ALE spaces.

hep-th↗

arXiv2015

Evidence for C-theorems in 6D SCFTs

Using the recently established classification of 6D SCFTs we present evidence for the existence of families of weak C-functions, that is, quantities which decrease in a flow from the UV to the IR. Introducing a background R-symmetry field strength R and a non-trivial tangent bundle T on the 6D spacetime, we consider C-functions given by the linear combinations C = m1 alpha + m2 beta + m3 gamma, where alpha, beta and gamma are the anomaly polynomial coefficients for the formal characteristic classes c2(R)^2, c2(R)p1(T) and p1(T)^2. By performing a detailed sweep over many theories, we determine the shape of the unbounded monotonic region in "m-space" compatible with both Higgs branch flows and tensor branch flows. We also verify that --as expected-- the Euler density conformal anomaly falls in the admissible region.

hep-th↗

arXiv2015

Atomic Classification of 6D SCFTs

We use F-theory to classify possibly all six-dimensional superconformal field theories (SCFTs). This involves a two step process: We first classify all possible tensor branches allowed in F-theory (which correspond to allowed collections of contractible spheres) and then classify all possible configurations of seven-branes wrapped over them. We describe the first step in terms of "atoms" joined into "radicals" and "molecules," using an analogy from chemistry. The second step has an interpretation via quiver-type gauge theories constrained by anomaly cancellation. A very surprising outcome of our analysis is that all of these tensor branches have the structure of a linear chain of intersecting spheres with a small amount of possible decoration at the two ends. The resulting structure of these SCFTs takes the form of a generalized quiver consisting of ADE-type nodes joined by conformal matter. A collection of highly non-trivial examples involving E8 small instantons probing an ADE singularity is shown to have an F-theory realization. This yields a classification of homomorphisms from ADE subgroups of SU(2) into E8 in purely geometric terms, largely matching results obtained in the mathematics literature from an intricate group theory analysis.

hep-th↗

arXiv2015

On the Possibility of Large Axion Moduli Spaces

We study the diameters of axion moduli spaces, focusing primarily on type IIB compactifications on Calabi-Yau three-folds. In this case, we derive a stringent bound on the diameter in the large volume region of parameter space for Calabi-Yaus with simplicial Kähler cone. This bound can be violated by Calabi-Yaus with non-simplicial Kähler cones, but additional contributions are introduced to the effective action which can restrict the field range accessible to the axions. We perform a statistical analysis of simulated moduli spaces, finding in all cases that these additional contributions restrict the diameter so that these moduli spaces are no more likely to yield successful inflation than those with simplicial Kähler cone or with far fewer axions. Further heuristic arguments for axions in other corners of the duality web suggest that the difficulty observed in hep-th/0303252 of finding an axion decay constant parametrically larger than $M_p$ applies not only to individual axions, but to the diagonals of axion moduli space as well. This observation is shown to follow from the weak gravity conjecture of hep-th/0601001, so it likely applies not only to axions in string theory, but also to axions in any consistent theory of quantum gravity.

hep-th↗

arXiv2015

On the Defect Group of a 6D SCFT

We use the F-theory realization of 6D superconformal field theories (SCFTs) to study the corresponding spectrum of stringlike, i.e. surface defects. On the tensor branch, all of the stringlike excitations pick up a finite tension, and there is a corresponding lattice of string charges, as well as a dual lattice of charges for the surface defects. The defect group is data intrinsic to the SCFT and measures the surface defect charges which are not screened by dynamical strings. When non-trivial, it indicates that the associated theory has a partition vector rather than a partition function. We compute the defect group for all known 6D SCFTs, and find that it is just the abelianization of the discrete subgroup of U(2) which appears in the classification of 6D SCFTs realized in F-theory. We also explain how the defect group specifies defining data in the compactification of a (1,0) SCFT.

hep-th↗

arXiv2014

A Meta-analysis of the 8 TeV ATLAS and CMS SUSY Searches

Between the ATLAS and CMS collaborations at the LHC, hundreds of individual event selections have been measured in the data to look for evidence of supersymmetry at a center of mass energy of 8 TeV. While there is currently no significant evidence for any particular model of supersymmetry, the large number of searches should have produced some large statistical fluctuations. By analyzing the distribution of p-values from the various searches, we determine that the number of excesses is consistent with the Standard Model only hypothesis. However, we do find a shortage of signal regions with far fewer observed events than expected in both the ATLAS and CMS datasets (at $1.65σ$ and $2.77σ$, respectively). While not as compelling as a surplus of excesses, the lack of deficits could be a hint of new physics already in the 8 TeV datasets.

hep-ph↗

arXiv2012

Evidence for Conservatism in LHC SUSY Searches

The standard in the high energy physics community for claiming discovery of new physics is a $5σ$ excess in the observed signal over the estimated background. While a $3σ$ excess is not enough to claim discovery, it is certainly enough to pique the interest of both experimentalists and theorists. However, with a large number of searches performed by both the ATLAS and CMS collaborations at the LHC, one expects a nonzero number of multi-$σ$ results simply due to statistical fluctuations in the no-signal scenario. Our analysis examines the distribution of p-values for CMS and ATLAS supersymmetry (SUSY) searches using the full 2011 data set to determine if the collaborations are being overly conservative in their analyses. We find that there is a statistically significant excess of `medium' $σ$ values at the level of $p=0.005$, indicating over-conservativism in the estimation of uncertainties.

stat.AP↗