Rick Sandeepan Gupta

We present a minimal cosmological solution to the hierarchy problem. Our model consists of a light pseudoscalar and an extra Higgs doublet in addition to the standard model field content. We consider a landscape of vacua with varying values of the electroweak vacuum expectation value (VEV). The vacuum energy in our model peaks in a region of the landscape where the electroweak VEV is nonzero and much smaller than the cutoff. During inflation, due to exponential expansion, such regions of the landscape with maximal vacuum energy dominate the universe in volume, thus explaining the observed smallness of the electroweak scale with respect to the cutoff. The pseudoscalar potential in our model is that of a completely generic pseudogoldstone boson—not requiring the clockwork mechanism—and its field value never exceeds its decay constant or the Planck scale. Our mechanism is robust to the variation of other model parameters in the landscape as the electroweak VEV is varied. It also predicts a precise and falsifiable relationship between the masses and couplings of the different Higgs boson mass eigenstates. Moreover, the pseudoscalar in our model can account for the observed dark matter relic density. Published by the American Physical Society 2025

The S U ( 2 ) L × U ( 1 ) Y invariance of the Standard Model effective field theory (SMEFT) predicts multiple restrictions in the space of Wilson coefficients of U ( 1 ) e m invariant effective Lagrangians such as the low-energy effective field theory (LEFT), used for low-energy flavor physics observables, or the Higgs effective field theory (HEFT) in unitary gauge, appropriate for weak-scale observables. In this work, we derive and list all such predictions for semileptonic operators up to dimension 6. These predictions can be expressed as linear relations among the HEFT/LEFT Wilson coefficients (WCs), that are completely independent of any assumptions about the alignment of the mass and flavor bases. We find seven sets of relations among the WCs of vector operators, nine sets with scalar and tensor operators, and two sets with the Z , W ± couplings. These correspond to 2223 linear relations among the complex WCs when the quark and lepton generation indices are included. They connect diverse experimental searches such as rare meson decays, high- p T dilepton searches, top decays, Z -pole observables, charged lepton flavor violating observables, and nonstandard neutrino interaction searches. We demonstrate how these relations can be used to derive strong indirect constraints on multiple WCs that are currently either weakly constrained from direct experiments or have no direct bound at all. They also imply, in general, that evidence for new physics in a particular search channel must be accompanied by correlated anomalies in other channels. For example, the observed excess in B → K ν ν ¯ would imply possible anomalies in B → D ( * ) ℓ ν ℓ , B → K ( * ) ℓ + ℓ − , B q → τ ν τ , B s → τ + τ − , D s → τ + ν τ , t → c ℓ + ℓ − , t → u ℓ + ℓ − , etc., correlated according to the relations obtained in this paper.

We present a minimal cosmological solution to the hierarchy problem. Our model consists of a light pseudoscalar and an extra Higgs doublet in addition to the field content of the Standard Model. We consider a landscape of vacua with varying values of the electroweak vacuum expectation value (VEV). The vacuum energy in our model peaks in a region of the landscape where the electroweak VEV is non-zero and much smaller than the cutoff. During inflation, due to exponential expansion, such regions of the landscape with maximal vacuum energy, dominate the universe in volume, thus explaining the smallness of the electroweak scale with respect to the cutoff. The pseudoscalar potential in our model is that of a completely generic pseudogoldstone boson$-$not requiring the clockwork mechanism$-$and its field value never exceeds its decay constant or the Planck scale. Our mechanism is robust to the variation of other model parameters in the landscape along with the electroweak VEV. It also predicts a precise and falsifiable relationship between the masses and couplings of the different Higgs boson mass-eigenstates. Moreover, the pseudoscalar in our model can account for the observed dark matter relic density.

Time and space translation invariance, giving rise to energy and momentum conservation, are not only amongst the most fundamental but also the most generally accepted symmetry assumptions in physics. It is nevertheless prudent to put such assumptions to experimental and observational tests. In this note, we take the first step in this direction, specifying a simple periodic time dependence that violates time translation invariance in QED, and setting phenomenological constraints on it. In addition to observational and experimental constraints on time varying couplings, we focus on probes of violation of energy conservation such as spontaneous production of photon and electron pairs and the e → eγ process. We discuss similarities and differences to the discussion of time varying fundamental constants and to the case of a light bosonic dark matter field that usually also causes oscillating effects.

A bstract: We investigate the dynamics responsible for generating the potential of the η ^′ , the (would-be) Goldstone boson associated with the anomalous axial U(1) symmetry of QCD. The standard lore posits that pure QCD dynamics generates a confining potential with a branched structure as a function of the θ angle, and that this same potential largely determines the properties of the η ^′ once fermions are included. Here we test this picture by examining a supersymmetric extension of QCD with a small amount of supersymmetry breaking generated via anomaly mediation. For pure SU( N ) QCD without flavors, we verify that there are N branches generated by gaugino condensation. Once quarks are introduced, the flavor effects qualitatively change the strong dynamics of the pure theory. For F flavors we find | N − F | branches, whose dynamical origin is gaugino condensation in the unbroken subgroup for F < N – 1, and in the dual gauge group for F > N + 1. For the special cases of F = N – 1, N , N + 1 we find no branches and the entire potential is consistent with being a one-instanton effect. The number of branches is a simple consequence of the selection rules of an anomalous U(1) _R symmetry. We find that the η ^′ mass does not vanish in the large N limit for fixed F / N , since the anomaly is non-vanishing. The same dynamics that is responsible for the η ^′ potential is also responsible for the axion potential. We present a simple derivation of the axion mass formula for an arbitrary number of flavors.