A
bstract
We present the first complete next-to-next-to-leading order analysis of the Standard Model Higgs potential. We computed the two-loop QCD and Yukawa corrections to the relation between the ...Higgs quartic coupling (
λ
) and the Higgs mass (
M
h
), reducing the theoretical uncertainty in the determination of the critical value of
M
h
for vacuum stability to 1 GeV. While
λ
at the Planck scale is remarkably close to zero, absolute stability of the Higgs potential is excluded at 98 % C.L. for
M
h
<
126 GeV. Possible consequences of the near vanishing of
λ
at the Planck scale, including speculations about the role of the Higgs field during inflation, are discussed.
We update instability and metastability bounds of the Standard Model electroweak vacuum in view of the recent ATLAS and CMS Higgs results. For a Higgs mass in the range 124–126 GeV, and for the ...current central values of the top mass and strong coupling constant, the Higgs potential develops an instability around 1011 GeV, with a lifetime much longer than the age of the Universe. However, taking into account theoretical and experimental errors, stability up to the Planck scale cannot be excluded. Stability at finite temperature implies an upper bound on the reheat temperature after inflation, which depends critically on the precise values of the Higgs and top masses. A Higgs mass in the range 124–126 GeV is compatible with very high values of the reheating temperature, without conflict with mechanisms of baryogenesis such as leptogenesis. We derive an upper bound on the mass of heavy right-handed neutrinos by requiring that their Yukawa couplings do not destabilize the Higgs potential.
A
bstract
Hamiltonian Truncation (a.k.a. Truncated Spectrum Approach) is an efficient numerical technique to solve strongly coupled QFTs in
d
= 2 spacetime dimensions. Further theoretical ...developments are needed to increase its accuracy and the range of applicability. With this goal in mind, here we present a new variant of Hamiltonian Truncation which exhibits smaller dependence on the UV cutoff than other existing implementations, and yields more accurate spectra. The key idea for achieving this consists in integrating out exactly a certain class of high energy states, which corresponds to performing renormalization at the cubic order in the interaction strength. We test the new method on the strongly coupled two-dimensional quartic scalar theory. Our work will also be useful for the future goal of extending Hamiltonian Truncation to higher dimensions
d
≥ 3.
A
bstract
We show how a heavy scalar singlet with a large vacuum expectation value can evade the potential instability of the Standard Model electroweak vacuum. The quartic interaction between the ...heavy scalar singlet and the Higgs doublet leads to a positive tree-level threshold correction for the Higgs quartic coupling, which is very effective in stabilizing the potential. We provide examples, such as the see-saw, invisible axion and unitarized Higgs inflation, where the proposed mechanism is automatically implemented in well-defined ranges of Higgs masses.
Scaling and tuning of EW and Higgs observables Elias-Miró, Joan; Grojean, Christophe; Gupta, Rick S. ...
The journal of high energy physics,
05/2014, Letnik:
2014, Številka:
5
Journal Article
Recenzirano
Odprti dostop
A
bstract
We study deformations of the SM via higher dimensional operators. In particular, we explicitly calculate the one-loop anomalous dimension matrix for 13 bosonic dimension-6 operators ...relevant for electroweak and Higgs physics. These scaling equations allow us to derive RG-induced bounds, stronger than the direct constraints, on a universal shift of the Higgs couplings and some anomalous triple gauge couplings by assuming no tuning at the scale of new physics, i.e. by requiring that their individual contributions to the running of other severely constrained observables, like the electroweak oblique parameters or Γ(
h
→
γγ
), do not exceed their experimental direct bounds. We also study operators involving the Higgs and gluon fields.
A
bstract
Hamiltonian Truncation (HT) is a numerical approach for calculating observables in a Quantum Field Theory non-perturbatively. This approach can be applied to theories constructed by ...deforming a conformal field theory with a relevant operator of scaling dimension ∆. UV divergences arise when ∆ is larger than half of the spacetime dimension
d
. These divergences can be regulated by HT or by using a more conventional local regulator. In this work we show that extra UV divergences appear when using HT rather than a local regulator for ∆ ≥
d/
2 + 1
/
4, revealing a striking breakdown of locality. Our claim is based on the analysis of conformal perturbation theory up to fourth order. As an example we compute the Casimir energy of
d
= 2 Minimal Models perturbed by operators whose dimensions take values on either side of the threshold
d/
2 + 1
/
4.
After an initial phase of firefighting against the euro crisis that began in 2010, one that was characterized by policies that focused on strict austerity, from 2014 onwards the European Commission ...gradually began to ease its recommendations about fiscal consolidation. Between 2015 and 2016, this policy turn was reflected in series of procedural changes in the European Semester. These gave the Commission a certain degree of discretion in applying the rules and interpreting the benchmarks of the post-crisis EU economic governance arrangements. This article investigates if this double shift in fiscal policy and governance that was initiated in 2014 has been consolidated in 2019, and, if so, what has driven that consolidation. By building on the literatures on EU politicization and policy learning, it asks whether the character of this intra-paradigm policy shift has been more Bayesian or sociological. Based on interviews and on a small-scale survey conducted with key civil servants working at the European Commission, we find evidence to support the putative explanation that, through a political process of policy learning, European Semester officials have acquired a more politicized and flexible practice of fiscal governance and a more social vision of the European Semester.
A
bstract
Lepton Flavor Violating (LFV) observables such as
μ
→
eγ
,
μ
→ 3
e
and
μN
→
eN
are among the best probes for new physics at the TeV scale. In the near future the bounds on these observables ...will improve by many orders of magnitude. In this work we use the SM EFT to understand the impact of these measurements. The precision reach is such that the interpretation of the bounds requires an analysis of the dimension-six operator mixing up to the two-loop level. Using on-shell amplitude techniques, which make transparent many selection rules, we classify and calculate the different operator mixing chains. At the leading order, on-shell techniques allow to calculate anomalous dimensions of SM EFT operators from the product of tree-level amplitudes, even for two-loop renormalization group mixings. We illustrate the importance of our EFT approach in models with extra vector-like fermions.
We find the complete set of conditions satisfied by the forward 2 → 2 scattering amplitude in unitary and causal theories. These are based on an infinite set of energy dependent quantities (the arcs) ...which are dispersively expressed as moments of a positive measure defined at (arbitrarily) higher energies. We identify optimal finite subsets of constraints, suitable to bound effective field theories (EFTs), at any finite order in the energy expansion. At tree level arcs are in a one to one correspondence with Wilson coefficients. We establish under which conditions this approximation applies, identifying seemingly viable EFTs where it never does. In all cases, we discuss the range of validity in both energy and couplings, where the latter has to satisfy two-sided bounds. We also extend our results to the case of small but finite t . A consequence of our study is that EFTs in which the scattering amplitude in some regime grows in energy faster than E6 cannot be UV completed.
This article traces the emergence of a novel interpretive platform in EU politics, one that understands that an array of post-Great Recession changes in the global political economy are calling for a ...reassessment of the EU's long-established approach to globalisation. The article argues that this rethinking is organised around the concept of "open strategic autonomy", by which is meant an endeavour to reduce the EU's external dependencies in a range of critical sectors. The article identifies the conceptual bases that inform the quest for strategic autonomy by examining the reforms prompted by this quest in industrial, competition, trade, digital, financial and defence policy. A conclusion arising from the analysis is that the relationship between European integration and global capitalism does not only concern the external policy domains of the EU, but also internal ones, in fact having key implications for the political economy of state intervention at the EU level.
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