arXiv subjects

C. Tamarit

Publications and source records attributed to C. Tamarit.

16 recordsLinked to original sources

arXiv2017

Standard Model - Axion - Seesaw - H portal inflation

Extending the Standard Model with a new complex singlet scalar, right-handed neutrinos and a vector-like quark allows to simultaneously tackle several problems in particle physics and cosmology within a constrained framework that can be falsified by future probes of the cosmic microwave background, as well as by upcoming axion experiments. This Standard Model - Axion - Seesaw - H portal inflation theory (SMASH) provides predictive inflation and $H$ boson stabilization, and can explain baryogenesis, light neutrino masses, dark matter and the strong CP problem. The model contains a unique new mass scale which coincides with the axion decay constant, and also sets the scale for perturbative lepton-number violation processes. Testable predictions include a minimum value of the tensor-to-scalar ratio of $r\gtrsim 0.004$, a running of the spectral index $\alpha\gtrsim-8\times10^{-4}$, a change $\delta N_{\rm eff}\sim 0.03$ in the number of effective relativistic neutrinos, and an axion mass in the range $50\mu eV\leq m_A \leq 200 \mu eV$.

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arXiv2014

Decoupling heavy sparticles in hierarchical SUSY scenarios: Two-loop Renormalization Group equations

Two loop renormalization group equations for dimensionless as well as dimensionful parameters are obtained for the low energy theories that result from decoupling heavy scalar particles in Split SUSY and Effective SUSY scenarios, assuming that only a single Higgs field survives at low energy. For the Effective SUSY case two scenarios are considered: first, when the only light third generation scalars are the partners of the left-handed quark doublet and the right-handed top quark --which yields the minimal matter content compatible with naturalness-- and second, when all the scalars of the third generation are light. These beta functions implementing decoupling will be useful to avoid the problems of perturbation theory in the MSSM in a mass-independent scheme such as DR-bar when large hierarchies in the spectrum are present.

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arXiv2012

Large, negative threshold contributions to light soft masses in models with Effective Supersymmetry

Threshold contributions to light scalar soft masses due to heavy sparticles (possibly including a heavy Higgs mostly aligned with H_d) in Effective SUSY scenarios are dominated by two-loop diagrams involving gauge couplings. This is due to the fact that in the limit in which the heavy states are degenerate, their one-loop contributions to the light soft masses only depend on small Yukawas and the hypercharge coupling. The two-loop threshold corrections involving only gauge couplings are calculated accounting for nonzero gaugino and light squark masses and shown to be negative, and rather large (δm^2_{t,L}\sim-480^2 GeV^2 for heavy sparticles with masses around 10 TeV). The effect on tachyon bounds is revisited with calculations implementing decoupling. It is pointed out that models yielding Effective SUSY spectra using gaugino mediation require in general very heavy gluinos or a very low SUSY breaking scale in order to avoid tachyons (e.g. for heavy squarks at 10 TeV and a SUSY breaking scale of 125 TeV, minimal scenarios require \tilde m_3 >=2 TeV at 500 GeV, while nonminimal ones demand \tilde m_3 >= 8 TeV).

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arXiv2012

Decoupling heavy sparticles in Effective SUSY scenarios: Unification, Higgs masses and tachyon bounds

Using two-loop renormalization group equations implementing the decoupling of heavy scalars, Effective SUSY scenarios are studied in the limit in which there is a single low energy Higgs field. Gauge coupling unification is shown to hold with similar or better precision than in standard MSSM scenarios. b-tau unification is examined, and Higgs masses are computed using the effective potential, including two-loop contributions from scalars. A 125 GeV Higgs is compatible with stops/sbottoms at around 300 GeV with non-universal boundary conditions at the scale of the heavy sparticles if some of the trilinear couplings at this scale take values of the order of 1-2 TeV; if more constrained boundary conditions inspired by msugra or gauge mediation are set at a higher scale, heavier colored sparticles are required in general. Finally, since the decoupled RG flow for third-generation scalar masses departs very significantly from the MSSM DR-bar one, tachyon bounds for light scalars are revisited and shown to be relaxed by up to a TeV or more.

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arXiv2010

Noncommutative GUT inspired theories with U(1), SU(N) groups and their renormalisability

We consider the GUT compatible formulation of noncommutative QED, as well as noncommutative SU(N) GUTs, for N>2, with no scalars but with fermionic matter in an arbitrary, anomaly-free representation, in the enveloping algebra approach. We compute, to first order in the noncommutativity parameters theta, the UV divergent part of the one-loop background-field effective action involving at most two fermion fields and an arbitrary number of gauge fields. It turns out that, for special choices of the ambiguous trace over the gauge degrees of freedom, for which the O(theta) triple gauge-field interactions vanish, the divergences can be absorbed by means of multiplicative renormalisations and the inclusion of theta-dependent counterterms that vanish on-shell and are thus unphysical. For this to happen in the SU(N), N>2 case, the representations of the matter fields must have a common second Casimir; anomaly cancellation then requires the ordinary (commutative) matter content to be non-chiral. Together with the vanishing of the divergences of fermionic four point functions, this shows that GUT inspired theories with U(1) and SU(N), N>2 gauge groups and ordinary vector matter content not only have a renormalisable matter sector, but are on-shell one-loop multiplicatively renormalisable at order one in theta.

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arXiv2009

Renormalisability of noncommutative GUT inspired field theories with anomaly safe groups

We consider noncommutative GUT inspired field theories formulated within the enveloping-algebra formalism for anomaly safe compact simple gauge groups. Our theories have only gauge fields and fermions, and we compute the UV divergent part of the one-loop background-field effective action involving two fermionic fields at first order in the noncommutativity parameter theta. We show that, if the second-degree Casimir has the same value for all the irreps furnished by the fermionic multiplets of the model, then, that UV divergent part can be renormalised by carrying out multiplicative renormalisations of the coupling constant, theta and the fields, along with the inclusion of theta-dependent counterterms which vanish upon imposing the equations of motion. These theta-dependent counterterms have no physical effect since they vanish on-shell. This result along with the vanishing of the UV divergent part of the fermionic four-point functions leads to the unexpected conclusion that the one-loop matter sector of the background-field effective action of these theories is one-loop multiplicatively renormalisable on-shell. We also show that the background-field effective action of the gauge sector of the theories considered here receives no theta-dependent UV divergent contributions at one-loop. We thus conclude that these theories are on-shell one-loop multiplicatively renormalisable at first order in theta.

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arXiv2009

Noncommutative GUT inspired theories and the UV finiteness of the fermionic four point functions

We show at one-loop and first order in the noncommutativity parameters that in any noncommutative GUT inspired theory the total contribution to the fermionic four point functions coming only from the interaction between fermions and gauge bosons, though not UV finite by power counting, is UV finite at the end of the day. We also show that this is at odds with the general case for noncommutative gauge theories --chiral or otherwise-- defined by means of Seiberg-Witten maps that are the same --barring the gauge group representation-- for left-handed spinors as for right-handed spinors. We believe that the results presented in this paper tilt the scales to the side of noncommutative GUTS and noncommutative GUT inspired versions of the Standard Model.

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arXiv2009

Noncommutative N=1 super Yang-Mills, the Seiberg-Witten map and UV divergences

Classically, the dual under the Seiberg-Witten map of noncommutative U(N), {\cal N}=1 super Yang-Mills theory is a field theory with ordinary gauge symmetry whose fields carry, however, a θ-deformed nonlinear realisation of the {\cal N}=1 supersymmetry algebra in four dimensions. For the latter theory we work out at one-loop and first order in the noncommutative parameter matrix θ^{μν} the UV divergent part of its effective action in the background-field gauge, and, for N>=2, we show that for finite values of N the gauge sector fails to be renormalisable; however, in the large N limit the full theory is renormalisable, in keeping with the expectations raised by the quantum behaviour of the theory's noncommutative classical dual. We also obtain --for N>=3, the case with N=2 being trivial-- the UV divergent part of the effective action of the SU(N) noncommutative theory in the enveloping-algebra formalism that is obtained from the previous ordinary U(N) theory by removing the U(1) degrees of freedom. This noncommutative SU(N) theory is also renormalisable.

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arXiv2009

Noncommutative fermions and quarkonia decays

The recent introduction of a deformed non-minimal version of the noncommutative Standard Model in the enveloping-algebra approach, having a one-loop renormalisable gauge sector involving a higher order gauge term, motivates us to consider the possibility of extending the fermion sector with additional deformations, i.e. higher order fermionic terms. Since the renormalisability properties of the fermion sector of the model are not yet fully known, we work with an effective fermion lagrangian which includes noncommutative higher order terms involving a contraction with the noncommutative $θ$ tensor aside from the star products, so that these terms annihilate in the commutative limit. Some of these terms violate CPT in the weak sector, and some violate CP in the strong and hypercharge sectors. We apply this framework to the reevaluation of the decay rates of quarkonia (\bar{q}q_{1} = J/ψ, Υ) into two photons. These decays, which are forbidden in the ordinary Standard Model, had been previously studied as possible signals for noncommutativity, but not in the framework of the better behaved deformed non-minimal version of the noncommutative Standard Model. Weak CPT or strong-hypercharge CP violating interactions do not contribute to the result. If the parameters of the model take natural values, for the vast majority of configurations the resulting branching ratios are enhanced with respect to their values in the minimal version of the noncommutative Standard Model. Also for more than half of the parameter space, the rates are larger than the maximal rates that were calculated in the undeformed version of the non-minimal noncommutative Standard Model. Tuning the dimensionless parameters the predicted branching ratios can fall within the current experimental bounds.

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arXiv2008

The Seiberg-Witten map and supersymmetry

The lack of any local solution to the first-order-in-h omegamn Seiberg-Witten (SW) map equations for U(1) vector superfields compels us to obtain the most general solution to those equations that is a quadratic polynomial in the ordinary vector superfield, v, its chiral and antichiral projections and the susy covariant derivatives of them all. Furnished with this solution, which is local in the susy Landau gauge, we construct an ordinary dual of noncommutative U(1) SYM in terms of ordinary fields which carry a linear representation of the N=1 susy algebra. By using the standard SW map for the N=1 U(1) gauge supermultiplet we define an ordinary U(1) gauge theory which is dual to noncommutative U(1) SYM in the WZ gauge. We show that the ordinary dual so obtained is supersymmetric, for, as we prove as we go along, the ordinary gauge and fermion fields that we use to define it carry a nonlinear representation of the N=1 susy algebra. We finally show that the two ordinary duals of noncommutative U(1) SYM introduced above are actually the same N=1 susy gauge theory. We also show in this paper that the standard SW map is never the theta theta--bar component of a local superfield in v and check that, at least at a given approximation, a suitable field redefinition of that map makes the noncommutative and ordinary --in a Bmn field-- susy U(1) DBI actions equivalent.

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arXiv2007

Renormalisability of the matter determinants in noncommutative gauge theory in the enveloping-algebra formalism

We consider noncommutative gauge theory defined by means of Seiberg-Witten maps for an arbitrary semisimple gauge group. We compute the one-loop UV divergent matter contributions to the gauge field effective action to all orders in the noncommutative parameters $θ$. We do this for Dirac fermions and complex scalars carrying arbitrary representations of the gauge group. We use path-integral methods in the framework of dimensional regularisation and consider arbitrary invertible Seiberg-Witten maps that are linear in the matter fields. Surprisingly, it turns out that the UV divergent parts of the matter contributions are proportional to the noncommutative Yang-Mills action where traces are taken over the representation of the matter fields; this result supports the need to include such traces in the classical action of the gauge sector of the noncommutative theory.

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arXiv2006

The noncommutative U(1) Higgs-Kibble model in the enveloping-algebra formalism and its renormalizability

We discuss the renormalizability of the noncommutative U(1)Higgs-Kibble model formulated within the enveloping-algebra approach. We consider both the phase of the model with unbroken gauge symmetry and the phase with spontaneously broken gauge symmetry. We show that against all odds the gauge sector of the model is always one-loop renormalizable at first order in theta^{mu nu}, perhaps, hinting at the existence of a new symmetry of the gauge sector of the model. However, we also show that the matter sector of the model is non-renormalizable whatever the phase.

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arXiv2006

Monopoles, noncommutative gauge theories in the BPS limit and some simple gauge groups

For three conspicuous gauge groups, namely, SU(2), SU(3) and SO(5), and at first order in the noncommutative parameter matrix hθ^{μν}, we construct smooth monopole --and, some two-monopole-- fields that solve the noncommutative Yang-Mills-Higgs equations in the BPS limit and that are formal power series in hθ^{μν}. We show that there exist noncommutative BPS (multi-)monopole field configurations that are formal power series in hθ^{μν} if, and only if, two a priori free parameters of the Seiberg-Witten map take very specific values. These parameters, that are not associated to field redefinitions nor to gauge transformations, have thus values that give rise to sharp physical effects.

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arXiv2006

Noncommutative QCD, first-order-in-theta-deformed instantons and 't Hooft vertices

For commutative Euclidean time, we study the existence of field configurations that {\it a)} are formal power series expansions in $hθ^{\m\n}$, {\it b)} go to ordinary (anti-)instantons as $hθ^{\m\n}\to 0$, and {\it c)} render stationary the classical action of Euclidean noncommutative SU(3) Yang-Mills theory. We show that the noncommutative (anti-)self-duality equations have no solutions of this type at any order in $hθ^{\m\n}$. However, we obtain all the deformations --called first-order-in-$θ$-deformed instantons-- of the ordinary instanton that, at first order in $hθ^{\m\n}$, satisfy the equations of motion of Euclidean noncommutative SU(3) Yang-Mills theory. We analyze the quantum effects that these field configurations give rise to in noncommutative SU(3) with one, two and three nearly massless flavours and compute the corresponding 't Hooft vertices, also, at first order in $hθ^{\m\n}$. Other issues analyzed in this paper are the existence at higher orders in $hθ^{\m\n}$ of topologically nontrivial solutions of the type mentioned above and the classification of the classical vacua of noncommutative SU(N) Yang-Mills theory that are power series in $hθ^{\m\n}$.

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arXiv2005

The U(1)A anomaly in noncommutative SU(N) theories

We work out the one-loop $U(1)_A$ anomaly for noncommutative SU(N) gauge theories up to second order in the noncommutative parameter $θ^{μν}$. We set $θ^{0i}=0$ and conclude that there is no breaking of the classical $U(1)_A$ symmetry of the theory coming from the contributions that are either linear or quadratic in $θ^{μν}$. Of course, the ordinary anomalous contributions will be still with us. We also show that the one-loop conservation of the nonsinglet currents holds at least up to second order in $θ^{μν}$. We adapt our results to noncommutative gauge theories with SO(N) and U(1) gauge groups.

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arXiv2005

Noncommutative SU(N) theories, the axial anomaly, Fujikawa's method and the Atiyah-Singer index

Fujikawa's method is employed to compute at first order in the noncommutative parameter the $U(1)_A$ anomaly for noncommutative SU(N). We consider the most general Seiberg-Witten map which commutes with hermiticity and complex conjugation and a noncommutative matrix parameter, $θ^{μν}$, which is of ``magnetic'' type. Our results for SU(N) can be readily generalized to cover the case of general nonsemisimple gauge groups when the symmetric Seiberg-Witten map is used. Connection with the Atiyah-Singer index theorem is also made.

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