Ufuk Aydemir

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• PhD, MSc
• Researcher at Middle East Technical University

In effective field theories it is common to identify the onset of new physics with the violation of tree-level unitarity. However, we show that this is parametrically incorrect in the case of chiral perturbation theory, and is probably theoretically incorrect in general. In the chiral theory, we explore perturbative unitarity violation as a functio...

We discuss a possible scale of gravitational origin at around 10 MeV, or 10 − 12 cm, which arises in the MacDowell–Mansouri formalism of gravity due to the topological Gauss–Bonnet term in the action, as pointed out by Bjorken several years ago. A length scale of the same size emerges also in the Kodama solution in gravity, which is known to be clo...

Motivated by the RD(*) anomalies, we investigate an SO(10) grand unification scenario where a charge −1/3 scalar leptoquark (S1) remains as the only new physics candidate at the TeV scale. This leptoquark along with the Standard Model (SM) Higgs doublet originates from the same ten-dimensional real scalar multiplet in the SO(10) grand unification f...

Primordial black holes that survive until the present have been considered as a dark matter candidate. In this paper we argue that primordial 2-2-hole remnants provide a more promising and testable alternative. 2-2-holes arise in quadratic gravity as a new family of classical solutions for ultracompact matter distributions and they possess the blac...

With the recent progress in observations of astrophysical black holes, it has become more important to understand in detail the physics of strongly gravitating horizonless objects. If the objects identified in the observations are indeed horizonless and ultracompact, high curvature effects may become important, and their explorations may be intimatel...

We investigate the particle production by the Nambu-Goldstone boson in the spontaneous baryogenesis scenario for large misalignment angles. Studying numerically the case of an arbitrary initial phase, we reproduce the cubic dependence on the initial value of the phase of baryon asymmetry in the case of small oscillations and present our results for...

Breaking diffeomorphism invariance has been motivated in the literature on several grounds, including the emergence of General Relativity (GR). For this to be a reliable possibility, in a theory with minor violations of general covariance, a healthy behavior is required that is only slightly different from that of GR. In this paper, the cosmologica...

We investigate the effects of an early cosmological period, dominated by primordial 2-2-holes, on axion dark matter. 2-2-holes emerge in quadratic gravity, a candidate theory of quantum gravity, as a new family of classical solutions for ultracompact matter distributions. These objects have a black hole exterior without an event horizon and hence,...

We investigate a $\mathrm{SO}(10)$ grand unification scenario where the complex 10-dimensional scalar multiplet, containing the Standard Model (SM) Higgs boson, resides at the TeV scale altogether. The resulting low-energy model is a 2-Higgs-doublet model augmented with two $S_1$-type leptoquarks. The gauge-coupling unification is achieved with onl...

With the recent progress in observations of astrophysical black holes, it has become more important to understand in detail the physics of strongly gravitating horizonless objects. If the objects identified in the observations are indeed horizonless and ultracompact, high curvature effects may come into play, and their explorations may be intimatel...

Primordial black holes have been considered attractive dark matter candidates, whereas some of the predictions rely heavily on the near-horizon physics that remains to be tested experimentally. As a concrete alternative,thermal 2-2-holes closely resemble black holes without event horizons. Being a probable endpoint of gravitational collapse, they p...

Primordial black holes have been considered as an attractive dark matter candidate, whereas some of the predictions heavily rely on the near-horizon physics that remains to be tested experimentally. As a concrete alternative, thermal 2-2-holes closely resemble black holes without event horizons. Being a probable endpoint of gravitational collapse,...

We discuss the astrophysical and cosmological implications of having primordial thermal 2-2-hole remnants as dark matter. Thermal 2-2-holes emanate in quadratic gravity as horizonless classical solutions for ultracompact distributions of relativistic thermal gas. In contrast to a large 2-2-hole that imitates the thermodynamic behaviour of a black...

We discuss the astrophysical and cosmological implications of having primordial thermal 2-2-hole remnants as dark matter. Thermal 2-2-holes emanate in quadratic gravity as horizonless classical solutions for ultracompact distributions of relativistic thermal gas. In contrast to a large 2-2-hole that imitates the thermodynamic behaviour of a black h...

Primordial black holes that survive until the present have been considered as a dark matter candidate. In this paper we argue that primordial 2-2-hole remnants provide a more promising and testable option. 2-2-holes arise in quadratic gravity as a new family of classical solutions for ultracompact matter distributions and they possess the black hol...

The Spectral Action Principle in noncommutative geometry derives the actions of the Standard Model and General Relativity (along with several other gravitational terms) by reconciling them in a geometric setting, and hence offers an explanation for their common origin. However, one of the requirements in the minimal formalism, unification of the ga...

The Spectral Action Principle in the noncommutative geometry framework provides simultaneous derivation of the actions of the Standard Model and General Relativity by reconciling them in a geometric setting, and hence offers an explanation for their common origin. However, one of the requirements in the minimal formalism, unification of the gauge c...

One of the explanations proposed for the recent rare $B$-decay anomalies is the existence of a scalar leptoquark. We investigate a grand unification scenario where a single, charge -1/3 scalar leptoquark ($S_1$) is present as the only new physics candidate at the TeV-scale. This leptoquark along with the Standard Model (SM) Higgs doublet originates...

The Spectral Action Principle in the noncommutative geometry framework provides simultaneous derivation of the actions of the Standard Model and General Relativity by reconciling them in a geometric setting, and hence offers an explanation for their common origin. However, one of the requirements in the minimal formalism, unification of the gauge c...

One of the explanations proposed for the recent rare B-decay anomalies is the existence of a scalar leptoquark. We investigate a grand unification scenario where a single, charge-1/3 scalar leptoquark (S 1) is present as the only new physics candidate at the TeV-scale. This leptoquark along with the Standard Model (SM) Higgs doublet originates from...

We discuss a possible scale of gravitational origin at around 10 MeV, or 10−12 cm, arisen in the MacDowell-Mansouri formalism of gravity due to the topological Gauss-Bonnet term in the action, pointed out by Bjorken several years ago. A length scale of the same size emerges also in the Kodama solution in gravity, which is known to be closely relate...

A bstract Motivated by possible scalar-leptoquark explanations of the recently reported B -decay anomalies, we investigate whether the required leptoquarks can be accommodated within models based on noncommutative geometry (NCG). The models considered have the gauge structure of Pati-Salam models, SU(4) × SU(2) L × SU(2) R , with gauge coupling uni...

Motivated by possible scalar-leptoquark explanations of the recently reported $B$-decay anomalies, we investigate whether the required leptoquarks can be accommodated within models based on noncommutative geometry (NCG). The models considered have the gauge structure of Pati-Salam models, $SU(4)\times SU(2)_L\times SU(2)_R$, with gauge coupling uni...

We investigate the possibility of TeV-scale scalars as low energy remnants arising in the non-supersymmetric SO(10) grand unification framework where the field content is minimal. We consider a scenario where the SO(10) gauge symmetry is broken into the gauge symmetry of the Standard Model (SM) through multiple stages of symmetry breaking, and a...

We discuss a possible scale of gravitational origin at around $10$ MeV, or $10^{-12}$ cm, arisen in the MacDowell-Mansouri formalism of gravity due to the topological Gauss-Bonnet term in the action, proposed by Bjorken several years ago, and named after Zeldovich. A length scale of the same size emerges also in the Kodama solution to gravity, whic...

We discuss a possible interpretation of the 750 GeV diphoton resonance, recently reported at the large hadron collider (LHC), within a class of SU(2)L ×SU(2)R ×SU(4) models with gauge coupling unification. The unification is imposed by the underlying noncommutative geometry (NCG), which in these models is extended to a left–right symmetric completi...

We analyze the compatibility of the recent LHC signals and the TeV-scale left–right model(s) in the minimal nonsupersymmetric SO(10) framework. We show that the models in which the Higgs content is selected based on the extended survival hypothesis do not allow the WR boson to be at the TeV-scale. By relaxing this conjecture, we investigate various...

We discuss a possible interpretation of the $750$ GeV diphoton resonance, recently reported at the LHC, within a class of Pati-Salam models with gauge coupling unification. The unification is imposed by the underlying non-commutative geometry (NCG), which in these models is extended to a left-right symmetric completion of the Standard Model (SM). W...

We investigate the possibility of TeV-scale scalars as low energy remnants arising in the non-supersymmetric $\mathrm{SO}(10)$ grand unification framework where the field content is minimal. We consider a scenario where the $\mathrm{SO}(10)$ gauge symmetry is broken into the gauge symmetry of the Standard Model (SM) through multiple stages of symme...

We analyze the compatibility of the unified left–right symmetric Pati–Salam models motivated by noncommutative geometry and the TeV-scale right-handed W boson suggested by recent LHC data. We find that the unification/matching conditions place conflicting demands on the symmetry breaking scales and that generating the required WR mass and coupling...

We analyze the compatibility of the recent LHC signals and the TeV-scale left-right model(s) in the minimal nonsupersymmetric $SO(10)$ framework. We show that the models in which the Higgs content is selected based on the extended survival hypothesis do not allow the $W_R$ boson to be at the TeV-scale. By relaxing this conjecture, we investigate va...

We analyze the compatibility of the unified left-right symmetric Pati-Salam models motivated by non-commutative geometry and the TeV scale right-handed W boson suggested by recent LHC data. We find that the unification/matching conditions place conflicting demands on the symmetry breaking scales and that generating the required W_R mass and couplin...

We discuss the physical implications of formulating the Standard Model (SM) in terms of the superconnection formalism involving the superalgebra su(2/1). In particular, we discuss the prediction of the Higgs mass according to the formalism and point out that it is ~170 GeV, in clear disagreement with experiment. To remedy this problem, we extend th...

We investigate the physical implications of formulating the electroweak (EW) part of the Standard Model (SM) in terms of a superconnection involving the supergroup SU(2/1). In particular, we relate the observed Higgs mass to new physics at around 4 TeV. The ultraviolet incompleteness of the superconnection approach points to its emergent nature. Th...

We present an example of a gauge-invariant Lagrangian that contains four derivatives and describes one massive, non-ghostlike, degree of freedom.

We motivate the concept of emergent gauge symmetry and discuss ways that this concept can be tested. The key idea is that if a symmetry is emergent, one should look for small violations of this symmetry because the underlying fundamental theory does not contain the symmetry. We describe our recent work implementing this idea in the gravity sector....

If general relativity is an emergent phenomenon, there may be small violations of diffeomorphism invariance. We propose a phenomenology of perturbatively small violations of general relativity by the inclusion of terms which break general covariance. These can be tested by matching to the Parametrized Post Newtonian (PPN) formalism. The most sensit...

We explore the available parameter space of the minimal vectorial standard model. In this theory, the gauge currents are initially vectorial but the Higgs sector produces chiral mass eigenstates, leading to a set of heavy right-handed mirror particles. We describe the phenomenology of the residual parameter space and suggest that the model will be...