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Michal Malinský

Publications and source records attributed to Michal Malinský.

At least 19 recordsLinked to original sources

Universal global analytic expansion for the 't Hooft-Polyakov monopole profiles

In this work we discuss in detail a global analytic expansion scheme for the solutions of the `t~Hooft-Polyakov monopole profile equations for arbitrary $λ/e^2>0$ based on the findings presented in a recent resurgence-oriented letter arXiv:2602.14620 [hep-th], which the present study significantly expands upon. A uniformly convergent functional perturbation series developed around universal, surprisingly simple, analytic non-perturbative background profiles corresponding to a partial resummation of the Borel-plane expansions suggested there, is constructed; a perfect match to what is known about the full solutions' local behaviour at zero and infinite radii is achieved, along with simple analytic prescriptions for the locally inaccessible numerical parameters therein.

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Resurgent structure of the 't Hooft-Polyakov monopole

In this letter we present a comprehensive analysis of the differential equations governing the spatial profile of the 't~Hooft-Polyakov monopole from the viewpoint of resurgence theory. We note that the universality of the gauge-component asymptotics, together with the relative simplicity of its Borel transform and the associated Volterra equations' kernels, gives rise to a perturbative expansion featuring a good control over the proliferation of the Borel-plane singularities to all orders, along with full information about the relevant logarithmic discontinuities. Moreover, its partial resummation reveals remarkably simple universal analytic non-perturbative background profiles, around which one can develop a uniformly convergent global perturbative expansion of the exact solutions for any $λ/e^2>0$. This also provides an analytic grip on the numerical parameters governing the expansions of both the gauge and scalar profile functions at the origin and at infinity.

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Baryogenesis through leptogenesis in the minimal flipped $SU(5)$ with radiative seesaw

The minimal flipped $SU(5)$ unification with the right-handed neutrino Majorana mass scale generated as a two-loop effect is arguably one of the most constrained models of perturbative baryon and lepton number violation currently on the market. This is namely due to its very simple scalar sector structure which, subject to perturbativity and non-tachyonicity bounds, leads to the emergence of characteristic flavour patterns providing interesting insights into proton decay phenomenology, neutrino physics etc. In this contribution, we discuss the potential impact of the baryon asymmetry of the Universe as an additional requirement imposed onto the already strongly constrained flavour structure of the model, focusing on thermal leptogenesis as its hypothetical primary source in this framework. Remarkably, this single extra condition leads, among other things, to a very interesting upper limit on the absolute neutrino mass scale which, in turn, renders the model potentially testable in the existing beta-decay experiments such as KATRIN.

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Thermal leptogenesis in minimal unified models

We review the status of thermal leptogenesis in the minimal $SU(5)\times U(1)$ and $SO(10)$ unified models under the assumption that the leptonic asymmetry generated in the out-of-equilibrium decays of heavy Majorana neutrinos (and its subsequent conversion into baryons via sphalerons) constitutes the primary source of baryon asymmetry of the Universe. In both cases, leptogenesis is shown to provide a strong extra constraint on the flavour structure of the model under consideration, leading to interesting and potentially testable phenomenological effects.

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Leptogenesis in the minimal flipped $SU(5)$ unification

We study the prospects of thermal leptogenesis in the framework of the minimal flipped $SU(5)$ unified model in which the RH neutrino mass scale emerges as a two-loop effect. Despite its strong suppression with respect to the unification scale which tends to disfavor leptogenesis in the standard Davidson-Ibarra regime (and a notoriously large washout of the $N_1$-generated asymmetry owing to a top-like Yukawa entry in the Dirac neutrino mass matrix) the desired $η_B\sim 6\times 10^{-10}$ can still be attained in several parts of the parameter space exhibiting interesting baryon and lepton number violation phenomenology. Remarkably enough, in all these regions the mass of the lightest LH neutrino is so low that it yields $m_β\lesssim 0.03$ eV for the effective neutrino mass measured in beta-decay, i.e., an order of magnitude below the design sensitivity limit of the KATRIN experiment. This makes the model potentially testable in the near future.

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The trouble with the minimal renormalizable SO(10) GUT

We scrutinize the physical viability of the minimal non-supersymmetric $\mathrm{SO}(10)$ GUT with the scalar sector $\mathbf{45}\oplus\mathbf{126}\oplus\mathbf{10}_{\mathbb{C}}$, in which the unified symmetry is broken by the former two representations, and a realistic Yukawa sector is supported by the last two. Alongside the known issue of a relatively low GUT scale (and thus overly fast proton decay) encountered in minimally fine-tuned scenarios, we identify a very general problem of the model: the inability to properly accommodate a Standard-Model-like low-energy Higgs doublet in the perturbative regime.

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Quantum nature of the minimal potentially realistic $\mathrm{SO}(10)$ Higgs model

We study several aspects of the quantum structure of the minimal potentially realistic renormalizable $\mathrm{SO}(10)$ Higgs model in which the $\mathbf{45}\oplus \mathbf{126}$ scalars spontaneously break the symmetry down to the Standard Model group $\mathrm{SU}(3)_{c}\times \mathrm{SU}(2)_{L}\times \mathrm{U}(1)_{Y}$. With a complete information about the one-loop corrections to the masses of all scalars in the theory and the one-loop beta functions governing the running of all dimensionless scalar self-couplings, the domains of the parameter space where the model can be treated perturbatively are established, along with improved bounds from the requirements of the SM vacuum stability and gauge coupling unification. We demonstrate that the model is fully consistent and potentially realistic only in very narrow regions of the parameter space corresponding to the breaking chains with well pronounced $\mathrm{SU}(4)_{C}\times \mathrm{SU}(2)_L\times \mathrm{U}(1)_R$ and $\mathrm{SU}(3)_{c}\times \mathrm{SU}(2)_L\times \mathrm{SU}(2)_R\times \mathrm{U}(1)_{B-L}$ intermediate symmetries, with a clear preference for the former case. Barring accidental fine-tunings in the scalar sector, this makes it possible to provide a very sharp prediction for the position of the unification scale and the value of the associated gauge coupling, with clear implications for the phenomenology of grand unified models based on this structure.

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A unified leptoquark model confronted with lepton non-universality in $B$-meson decays

The anomalies in the $B$-meson sector, in particular $R_{K^{(*)}}$ and $R_{D^{(*)}}$, are often interpreted as hints for physics beyond the Standard Model. To this end, leptoquarks or a heavy $Z'$ represent the most popular SM extensions which can explain the observations. However, adding these fields by hand is not very satisfactory as it does not address the big questions like a possible embedding into a unified gauge theory. On the other hand, light leptoquarks within a unified framework are challenging due to additional constraints such as lepton flavor violation. The existing accounts typically deal with this issue by providing estimates on the relevant couplings. In this letter we consider a complete model based on the $SU(4)_{\rm C}\otimes SU(2)_{\rm L}\otimes U(1)_{\rm R}$ gauge symmetry, a subgroup of $SO(10)$, featuring both scalar and vector leptoquarks. We demonstrate that this setup has, in principle, all the potential to accommodate $R_{K^{(*)}}$ and $R_{D^{(*)}}$ while respecting bounds from other sectors usually checked in this context. However, it turns out that $K_L \to e^{\pm} μ^{\mp}$ severely constraints not only the vector but also the scalar leptoquarks and, consequently, also the room for any sizeable deviations of $R_{K^{(*)}}$ from 1. We briefly comment on the options for extending the model in order to conform this constraint. Moreover, we present a simple criterion for all-orders proton stability within this class of models.

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Collider phenomenology of a unified leptoquark model

We demonstrate that in a recently proposed unified leptoquark model based on the gauge group $SU(4)_C\times SU(2)_L \times U(1)_R$ significant deviations from the Standard Model values of $R_K$ and $R_{K^*}$ can be accommodated without any need of extra heavy fermions. Low energy data, in particular lepton flavour violating $μ$ decays and $K_L\to e μ$, severely constrain the available parameter space. We show that in the allowed part of the parameter space (i) some of the lepton-flavour-violating tau decay branching ratios are predicted to be close to their current experimental limits. (ii) The underlying scalar leptoquarks can be probed at the LHC via their dominant decay modes into tau-leptons and electrons and the third generation quarks. (iii) The constraints from meson oscillations imply that the masses of scalar gluons, another pair of coloured multiplets around, have to be bigger than around 15 TeV and, thus, they can be probed only at a future 100 TeV collider. In both neutral and charged variants, these scalars decay predominantly into third generation quarks, with up to $O$(10\%) branching ratios into family-mixed final states. Besides that, we comment on the phenomenology of the scalar gluons in the current scenarios in the case that the $B$-decay anomalies eventually disappear.

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Flavorgenesis

We present a model where all fermions are contained in a single irreducible representation of an SU(19) gauge symmetry group. If there is only one scalar field, Yukawa interactions are controlled by a single number rather than by one or more $3\times3$ matrices of couplings. The low-energy concept of flavor emerges entirely from the scalar-sector parameters; more specifically, entries of the Standard Model Yukawa matrices are controlled by several vacuum expectation values.

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Lepton non-universality in $B$-decays in the minimal leptoquark gauge model

The anomalies in semileptonic $B$-decays are often attributed to new physics scenarios featuring leptoquark degrees of freedom. Attempts to accommodate all the deviations at once usually result in an elaborate model building way beyond the minimal scenarios containing the desired degrees of freedom. However, as it is far from clear whether all these signals (if any) survives the future experimental scrutiny, in this contribution we decided to take the opposite standpoint and review the actual room available for various $B$-decay anomalies within the very minimal low-energy leptoquark gauge model based on the $SU(4)_{C}\otimes SU(2)_{L}\otimes U(1)_{R}$ symmetry group.

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Hierarchy and decoupling

A large hierarchy between the electroweak scale and virtually any new scale of beyond-Standard-Model physics is often claimed to be unnatural. Sometimes, the apparent disparity between the measured Higgs mass and the size of the typical loop corrections encountered within such schemes is even interpretted as a profound indication that one should expect a remedy just behind the corner, probably in form of a new physics such as low-scale supersymmetry, new strong dynamics etc. In reality, all such potentially large corrections in the one- and two-point Green's functions cancel with each other in the physical Higgs mass $m_{H}$ which eventually turns out to be driven only by the electroweak VEV $v$. This, naively, may look like a miracle, the more that the standard perturbative approach often makes it irresistible to discuss the magnitudes of those corrections as if, individually, they were physically relevant. To shed some more light on this conundrum we advocate a method based on the symmetry properties of the Coleman-Weinberg effective potential which not only makes it very clear why $m_H\propto v$ to all orders in the perturbative expansion but, at the same time, it does not require any inspection of the explicit form of the tadpole equations whatsoever. Besides simplifying the calculations considerably it makes the "internal composition" of the VEV in terms of the high-scale parameters essentially irrelevant. We exemplify these findings on an extended series of specific simplified models in which the role of the heavy dynamics is played by all "reasonable" types of fields (barring gravity), i.e., by a heavy scalar, a heavy (Majorana) fermion and a heavy vector, respectively. We show that the dependence of $m_{H}$ on the heavy scale follows the expectation based on dynamical arguments such as the decoupling theorem.

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Flavour Structure of GUTs and Uncertainties in Proton Lifetime Estimates

We study the flavour aspects of proton lifetime estimates in simple Grand unified models paying particular attention to their inherent fragility due to the notorious lack of control of some of the key parameters governing the relevant hard-process amplitudes. Among these, the theoretical uncertainties in the flavour structure of the baryon and lepton number violating charged currents due to the potential higher-order effects afflicting the matching of the underlying Yukawa couplings to the low-energy data often play a prominent role. Focusing on the minimal variants of the most popular unified models we study the potential instabilities of the corresponding proton lifetime estimates based on the renormalizable-level Yukawa fits with respect to the Planck-scale induced flavour effects. In particular, we perform a detailed numerical analysis of all minimal $SO(10)$ Yukawa sector fits available in the literature and show that the proton lifetime estimates based on these inputs exhibit a high degree of robustness with respect to moderate-size perturbations, well within the expected "improvement window" of the upcoming proton decay searches.

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Witten's loop in the minimal flipped $SU(5)$ unification revisited

In the simplest potentially realistic renormalizable variants of the flipped $SU(5)$ unified model the right-handed neutrino masses are conveniently generated by means of the Witten's two-loop mechanism. As a consequence, the compactness of the underlying scalar sector provides strong correlations between the low-energy flavor observables such as neutrino masses and mixing and the flavor structure of the fermionic currents governing the baryon and lepton number violating nucleon decays. In this study, the associated two-loop Feynman integrals are fully evaluated and, subsequently, are used to draw quantitative conclusions about the central observables of interest such as the proton decay branching ratios and the absolute neutrino mass scale.

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Effects of ultra-light dark matter on the gravitational quantum well

We study the influence of a periodic perturbation of the effective masses of the nucleons, due to the assumed semi-classical ultra-light dark matter background, on the motion of neutrons in a gravitational quantum well. Our focus is on the transition probability between the lowest two energy states, with the Rabi frequency in the kHz region corresponding to the series of "sweet spot" dark matter masses in the $10^{-11}$eV ballpark. The relevant probability is written in terms of the specific mass and of the effective coupling to the ordinary matter. These parameters can be constrained by the non-observation of any significant deviations of the measured transition probabilities from the dark-matter-free picture.

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One-loop pseudo-Goldstone masses in the minimal $SO(10)$ Higgs model

We calculate the prominent perturbative contributions shaping the one-loop scalar spectrum of the minimal non-supersymmetric renormalizable $SO(10)$ Higgs model whose unified gauge symmetry is spontaneously broken by an adjoint scalar. Focusing on its potentially realistic $45\oplus 126$ variant in which the rank is reduced by a VEV of the 5-index self-dual antisymmetric tensor, we provide a thorough analysis of the corresponding one-loop Coleman-Weinberg potential, paying particular attention to the masses of the potentially tachyonic pseudo-Goldstone bosons (PGBs) transforming as $(8,1,0)$ and $(1,3,0)$ under the Standard Model gauge group. The results confirm the assumed existence of extended regions in the parameter space supporting a locally stable SM-like quantum vacuum inaccessible at the tree-level. The effective potential (EP) tedium is compared to that encountered in the previously studied $45\oplus 16$ $SO(10)$ Higgs model where the polynomial corrections to the relevant pseudo-Goldstone masses turn out to be easily calculable within a very simplified purely diagrammatic approach.

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Neutrino-axion-dilaton interconnection

We show that a recently proposed framework that provides a simple connection between Majorana neutrinos and an invisible axion in minimal scalar extensions of the standard electroweak model can be naturally embedded in a classically scale-invariant setup. The explicit breaking of the scale invariance à la Coleman-Weinberg generates the Peccei-Quinn and electroweak scales. The spontaneous breaking of the chiral $U(1)_{PQ}$ triggers the generation of neutrino masses via Type-II seesaw and, at the same time, provides a dynamical solution to the strong CP problem as well as the axion as a dark matter candidate. The electroweak and neutrino mass scales are obtained via a technically natural ultraweak limit of the singlet scalar interactions. Accordingly, a realistic and perturbatively stable scalar spectrum, possibly in the reach of the LHC, is naturally obtained. A very light pseudodilaton characterizes such a setting. The vacuum stability of the extended setup is discussed.

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Theoretical Uncertainties in Proton Lifetime Estimates

We recapitulate the primary sources of theoretical uncertainties in proton lifetime estimates in renormalizable, four-dimensional and non-supersymmetric grand unifications that represent the most conservative framework in which this question may be addressed at the perturbative level. We point out that many of these uncertainties are so severe that there are only very few scenarios in which an NLO approach, as crucial as it is for a real testability of any specific model, is actually sensible. Among these, the most promising seems to be the minimal renormalizable SO(10) GUT whose high-energy gauge symmetry is spontaneously broken by the adjoint and the five-index antisymmetric irreducible representations.

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