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Krzysztof A. Meissner

Publications and source records attributed to Krzysztof A. Meissner.

At least 37 records · Page 2Linked to original sources
arXiv2019

Test-field limit of metric nonlinear gravity theories

In the framework of alternative metric gravity theories, it has been shown by several authors that a generic Lagrangian depending on the Riemann tensor describes a theory with 8 degrees of freedom (which reduce to 3 for f(R) Lagrangians depending only on the curvature scalar). This result is often related to a reformulation of the fourth-order equations for the metric into a set of second-order equations for a multiplet of fields, including a massive scalar field and a massive spin-2 field. In this article we investigate an issue which does not seem to have been addressed so far: in ordinary general-relativistic field theories, all fundamental fields (i.e. fields with definite spin and mass) reduce to test fields in some appropriate limit of the model, where they cease to act as sources for the metric curvature. In this limit, each of the fundamental fields can be excited from its ground state independently from the others. The question is: does higher-derivative gravity admit a test-field limit for its fundamental fields? It is easy to show that for a f(R) theory the test-field limit does exist; then, we consider the case of Lagrangians quadratically depending on the full Ricci tensor. We show that the constraint binding together the scalar field and the massive spin-2 field does not disappear in the limit where they should be expected to act as test fields, except for a particular choice of the Lagrangian, which cause the scalar field to disappear (reducing to 7 DOF). We finally consider the addition of an arbitrary function of the quadratic invariant of the Weyl tensor and show that the resulting model still lacks a proper test-field limit. We argue that the lack of a test-field limit for the fundamental fields may constitute a serious drawback of the full 8 DOF higher-order gravity models, which is not encountered in the restricted 7 DOF or 3 DOF cases.

gr-qc↗
arXiv2018

Standard Model Fermions and Infinite-Dimensional R-Symmetries

Following up on our earlier work where we showed how to amend a scheme originally proposed by M. Gell-Mann to identify the 48 spin 1/2 fermions of N=8 supergravity that remain after complete breaking of N=8 supersymmetry with the 3x16 quarks and leptons of the Standard Model, we further generalize the construction to account for the full SU(3)_c x SU(2)_w x U(1)_Y assignments, with an additional family symmetry SU(3)_f. Our proposal relies in an essential way on embedding the SU(8) R-symmetry of N=8 supergravity into the (infinite-dimensional) `maximal compact' subgroup K(E10) of the conjectured maximal duality symmetry E10. As a by-product, it predicts fractionally charged and possibly strongly interacting massive gravitinos. It also indicates how E10 and K(E10) can supersede supersymmetry as a guiding principle for unification.

hep-th↗
arXiv2018

Conformal Standard Model and Inflation

This article presents a possible inflation scenario as a consequence of non-minimal gravitational couplings in the Conformal Standard Model. The model consists, in comparison to the SM, of additional right-chiral neutrinos and complex scalars coupled to the right-chiral neutrinos but not to the SM particles. The inflation is driven by two non-minimally coupled fields one being the usual Higgs and the other one of the sterile scalars. It turns out that in this model the tensor to scalar ratio and spectral index can match the current data for a wide range of parameters.

gr-qc↗
arXiv2018

Conformal Standard Model, Leptogenesis and Dark Matter

The Conformal Standard Model (CSM) is a minimal extension of the Standard Model of Particle Physics based on the assumed absence of large intermediate scales between the TeV scale and the Planck scale, which incorporates only right-chiral neutrinos and a new complex scalar in addition to the usual SM degrees of freedom, but no other features such as supersymmetric partners. In this paper, we present a comprehensive quantitative analysis of this model, and show that all outstanding issues of particle physics proper can in principle be solved `in one go' within this framework. This includes in particular the stabilization of the electroweak scale, `minimal' leptogenesis and the explanation of Dark Matter, with a small mass and very weakly interacting Majoron as the Dark Matter candidate (for which we propose to use the name `minoron'). The main testable prediction of the model is a new and almost sterile scalar boson that would manifest itself as a narrow resonance in the TeV region. We give a representative range of parameter values consistent with our assumptions and with observation.

hep-ph↗
arXiv2017

Conformal Anomaly and Off-Shell Extensions of Gravity

The gauge dependence of the conformal anomaly for spin 3/2 and spin 2 fields in non-conformal supergravities has been a long standing puzzle. In this Letter we argue that the `correct' gauge choice is the one that follows from requiring all terms that would imply a violation of the Wess-Zumino consistency condition to be absent in the counterterm, because otherwise the usual link between the anomaly and the one-loop divergence becomes invalid. Remarkably, the `good' choice of gauge is the one that confirms our previous result that a complete cancellation of conformal anomalies in D=4 can only be achieved for N-extended (Poincaré) supergravities with $N\geq 5$.

hep-th↗
arXiv2016

Conformal anomalies and the Einstein Field Equations

We compute corrections to the Einstein field equations which are induced by the anomalous effective actions associated to the type A conformal anomaly, both for the (non-local) Riegert action, as well as for the local action with dilaton. In all cases considered we find that these corrections can be very large.

hep-th↗
arXiv2016

Two-loop RGE of a general renormalizable Yang-Mills theory in a renormalization scheme with an explicit UV cutoff

We perform a systematic one-loop renormalization of a general renormalizable Yang-Mills theory coupled to scalars and fermions using a regularization scheme with a smooth momentum cutoff $Λ$ (implemented through an exponential damping factor). We construct the necessary finite counterterms restoring the BRST invariance of the effective action by analyzing the relevant Slavnov-Taylor identities. We find the relation between the renormalized parameters in our scheme and in the conventional $\overline{\rm MS}$ scheme which allow us to obtain the explicit two-loop renormalization group equations in our scheme from the known two-loop ones in the $\overline{\rm MS}$ scheme. We calculate in our scheme the divergences of two-loop vacuum graphs in the presence of a constant scalar background field which allow us to rederive the two-loop beta functions for parameters of the scalar potential. We also prove that consistent application of the proposed regularization leads to counterterms which, together with the original action, combine to a bare action expressed in terms of bare parameters. This, together with treating $Λ$ as an intrinsic scale of a hypothetical underlying finite theory of all interactions, offers a possibility of an unconventional solution to the hierarchy problem if no intermediate scales between the electroweak scale and the Planck scale exist.

hep-ph↗
arXiv2016

Conformal Anomalies and Gravitational Waves

We argue that the presence of conformal anomalies in gravitational theories can lead to observable modifications to Einstein's equations via the induced anomalous effective actions, whose non-localities can overwhelm the smallness of the Planck scale. The fact that no such effects have been seen in recent cosmological or gravitational wave observations therefore imposes strong restrictions on the field content of possible extensions of Einstein's theory: all viable theories should have vanishing conformal anomalies. We then show that a complete cancellation of conformal anomalies in D=4 for both the $C^2$ invariant and the Euler (Gauss-Bonnet) invariant can only be achieved for N-extended supergravities with $N \geq 5$, as well as for M theory compactified to four dimensions.

gr-qc↗
arXiv2016

Ring Type Structures in the Planck map of the CMB

We present the results of the quest for ring-type structures on the maps observed by the Planck satellite. The results show that the vicinity of one radius (γ = 0.14 radians) of the rings is distinguished. Twisting the circles into deformed ellipses gives a pronounced drop of significance with the increase of twisting.

astro-ph.CO↗
arXiv2016

Ultraviolet cutoffs and the photon mass

The momentum UV cutoff in Quantum Field Theory is usually treated as an auxiliary device allowing to obtain finite amplitudes satisfying all physical requirements. It is even absent (not explicit) in the most popular approach - the dimensional regularization. We point out that the momentum cutoff treated as a bona fide physical scale, presumably equal or related to the Planck scale, would lead to unacceptable predictions. One of the dangers is a non-zero mass of the photon. In the naive approach, even with the cutoff equal to the Planck scale, this mass would grossly exceed the existing experimental bounds. We present the actual calculation using a concrete realization of the physical cutoff and speculate about the way to restore gauge symmetry order by order in the inverse powers of the cutoff scale.

hep-th↗
arXiv2015

Conformal Standard Model with an extended scalar sector

We present an extended version of the Conformal Standard Model (characterized by the absence of any new intermediate scales between the electroweak scale and the Planck scale) with an enlarged scalar sector coupling to right-chiral neutrinos. The scalar potential and the Yukawa couplings involving only right-chiral neutrinos are invariant under a new global symmetry SU(3)$_N$ that complements the standard U(1)$_{B-L}$ symmetry, and is broken explicitly only by the Yukawa interaction, of order $10^{-6}$, coupling right-chiral neutrinos and the electroweak lepton doublets. We point out four main advantages of this enlargement, namely: (1) the economy of the (non-supersymmetric) Standard Model, and thus its observational success, is preserved; (2) thanks to the enlarged scalar sector the RG improved one-loop effective potential is everywhere positive with a stable global minimum, thereby avoiding the notorious instability of the Standard Model vacuum; (3) the pseudo-Goldstone bosons resulting from spontaneous breaking of the SU(3)$_N$ symmetry are natural Dark Matter candidates with calculable small masses and couplings; and (4) the Majorana Yukawa coupling matrix acquires a form naturally adapted to leptogenesis. The model is made perturbatively consistent up to the Planck scale by imposing the vanishing of quadratic divergences at the Planck scale (`softly broken conformal symmetry'). Observable consequences of the model occur mainly via the mixing of the new scalars and the standard model Higgs boson.

hep-ph↗
arXiv2015

Conformal transformations and the beginning of the Universe

We show that two consecutive Universes with positive cosmological constants filled with perfect fluids and conformal to the positive-spatial-curvature FLRW metric by an analytic conformal transformation have the following features implied by the Einstein equations: a) the fluids can only belong to 4 classes (radiation, dust and two other classes with negative pressures corresponding to a gas of strings and a gas of domain walls), b) the field equations on both sides of the future/eternity hypersurface exhibit certain duality with the Einstein Universe at the background, and c) both eons (one at the end, and the other at the beginning) are almost critical, so that the future eon is dominated by radiation and resembles the beginning of our Universe.

gr-qc↗
arXiv2015

Standard Model Fermions and N=8 supergravity

In a scheme originally proposed by M. Gell-Mann, and subsequently shown to be realized at the SU(3)xU(1) stationary point of maximal gauged SO(8) supergravity by N. Warner and one of the present authors, the 48 spin 1/2 fermions of the theory remaining after the removal of eight Goldstinos can be identified with the 48 quarks and leptons (including right-chiral neutrinos) of the Standard Model, provided one identifies the residual SU(3) with the diagonal subgroup of the color group SU(3)_c and a family symmetry SU(3)_f. However, there remained a systematic mismatch in the electric charges by a spurion charge of $\pm$1/6. We here identify the `missing' U(1) that rectifies this mismatch, and that takes a surprisingly simple, though unexpected form.

hep-th↗
arXiv2014

Softly broken conformal symmetry and the stability of the electroweak scale

We point out a novel possible mechanism by which the electroweak hierarchy problem can be avoided in the (effective) quantum field theory. Assuming the existence of a UV complete underlying fundamental theory and treating the cutoff scale $Λ$ of the effective field theory as a real physical scale we argue that the hierarchy problem would be solved if the coefficient in front of quadratic divergences vanished for some choice of $Λ$, and if the effective theory mass parameters fixed at $Λ$ by the fundamental theory were hierarchically smaller than $Λ$ itself. While this mechanism most probably cannot work in the Standard Model if the scale $Λ$ is to be close to the Planck scale, we show that it can work in a minimal extension (Conformal Standard Model) proposed recently for a different implementation of soft conformal symmetry breaking.

hep-ph↗
arXiv2013

A Tail Sensitive Test for Cumulative Distribution Functions

We propose a simple way of testing whether a given set of observations can come from a given theoretical cumulative distribution. In the test more weight is attached to the tails of the distribution than in the usual Kolmogorov or Smirnov tests. The respective probability distribution is derived.

math.ST↗