Stress-energy connection: Degravitating the vacuum energy

13th Regional Conference on Mathematical Physics; Antalya; Turkey; 27 October 2010 through 31 October 2010This talk summarizes recent studies on the gravitational properties of vacuum energy in a non-Riemannian geometry formed by the stress-energy tensor of vacuum, matter and radiation. Postulating that the gravitational effects of matter and radiation can be formulated by an appropriate modification of the spacetime connection, we obtain varied geometro-dynamical equations which properly comprise the usual gravitational field equations with, however, Planck-suppressed, non-local, higher-dimensional additional terms. The prime novelty brought about by the formalism is that, the vacuum energy does act not as the cosmological constant but as the source of the gravitational constant. The formalism thus deafens the cosmological constant problem by channeling vacuum energy to gravitational constant. Nevertheless, quantum gravitational effects, if any, restore the problem via the graviton and graviton-matter loops, and the mechanism proposed here falls short of taming such contributions to cosmological constant

Hidden Spin-3/2 Field in the Standard Model

Here we show that a massive spin-3/2 field can hide in the SM spectrum in a way revealing itself only virtually. We study collider signatures and loop effects of this field, and determine its role in Higgs inflation and its potential as Dark Matter. We show that this spin-3/2 field has a rich linear collider phenomenology and motivates consideration of a neutrino-Higgs collider. We also show that study of Higgs inflation, dark matter and dark energy can reveal more about the neutrino and dark sector.Comment: 8 pages, 8 figures, accepted for publication in Eur. Phys. J.

LEP Indications for Two Light Higgs Bosons and U(1)' Model

Reanalyses of LEP data have shown preference to two light CP-even Higgs bosons. We discuss implications of such a Higgs boson spectrum for the minimal supersymmetric model extended by a Standard Model singlet chiral superfield and an additional Abelian gauge invariance (the U(1)' model). We, in particular, determine parameter regions that lead to two light CP-even Higgs bosons while satisfying existing bounds on the mass and mixings of the extra vector boson. In these parameter regions, the pseudoscalar Higgs is found to be nearly degenerate in mass with either the lightest or next-to-lightest Higgs boson. Certain parameters of the U(1)' model such as the effective mu parameter are found to be significantly bounded by the LEP two-light-Higgs signal.Comment: 20 pp, 7 figs, 2 table

Kutu Enkesitli Sandviç Tipi Çelik Çaprazların Çevrimsel Yük Etkisindeki Davranışlarının Deneysel Olarak İncelenmesisi

Bu çalışmada, yapısal sistemlerde yanal yük taşıyıcı elemanlar olarak kullanılan, kutu enkesitli geleneksel çelik çapraz elemanların burkulma davranışının kontrolü için bir yöntem önerilmektedir. Önerilen yöntemde, kutu enkesitli çelik çapraz içten ve dıştan iki ayrı kutu profilin arasına yerleştirilerek sandviç tipi bir çelik çapraz eleman elde edilmiştir. Burkulma kontrolünü sağlamak için kullanılan iç ve dış profillerin boyu yanal yük taşıyıcı elemanın boyundan daha kısa bırakılarak, bu profillerin eksenel yük taşımaları engellenmiştir. Deneysel çalışmalar kapsamında bir adet kutu enkesitli sandviç tipi çelik çapraz ile aynı özelliklerdeki kutu enkesitli profilden üretilmiş bir geleneksel çelik çapraz çevrimsel yük etkisinde test edilmiştir. Elde edilen bulgular yük taşıma kapasitesi, burkulma yerdeğiştirmesi ve enerji tüketme kapasitesi açısından karşılaştırılmalı olarak incelenmiştir. Sonuç olarak, önerilen burkulma kontrolü tasarımının, geleneksel çelik çaprazların yük taşıma kapasitesini, burkulma yerdeğiştirmesini ve enerji tüketme kapasitesini artırdığı belirlenmiştir

Testing Symmergent gravity through the shadow image and weak field photon deflection by a rotating black hole using the M87∗^* and Sgr. A∗^* results

In this paper, we study rotating black holes in symmergent gravity, and use deviations from the Kerr black hole to constrain the parameters of the symmergent gravity. Symmergent gravity induces the gravitational constant $G$ and quadratic curvature coefficient $c_{\rm O}$ from the flat spacetime matter loops. In the limit in which all fields are degenerate in mass, the vacuum energy $V_{\rm O}$ can be wholly expressed in terms of $G$ and $c_{\rm O}$. We parametrize deviation from this degenerate limit by a parameter ${\hat \alpha}$ such that the black hole spacetime is dS for ${\hat \alpha} < 1$ and AdS for ${\hat \alpha} > 1$. In constraining the symmergent parameters $c_{\rm O}$ and ${\hat \alpha}$, we utilize the EHT observations on the M87* and Sgr. A* black holes. We investigate first the modifications in the photon sphere and shadow size, and find significant deviations in the photonsphere radius and the shadow radius with respect to the Kerr solution. We also find that the geodesics of time-like particles are more sensitive to symmergent gravity effects than the null geodesics. Finally, we analyze the weak field limit of the deflection angle, where we use the Gauss-Bonnet theorem for taking into account the finite distance of the source and the receiver to the lensing object. Remarkably, the distance of the receiver (or source) from the lensing object greatly influences the deflection angle. Moreover, $c_{\rm O}$ needs be negative for a consistent solution. In our analysis, the rotating black hole acts as a particle accelerator and possesses the sensitivity to probe the symmergent gravity.Comment: 22 pages, 9 figures, 2 tables. Accepted for publication in the European Physical Journal C (https://link.springer.com/article/10.1140/epjc/s10052-023-11400-6

Dirac Neutrino Masses from Generalized Supersymmetry Breaking

We demonstrate that Dirac neutrino masses in the experimentally preferred range are generated within supersymmetric gauge extensions of the Standard Model with a generalized supersymmetry breaking sector. If the usual superpotential Yukawa couplings are forbidden by the additional gauge symmetry (such as a U(1)'), effective Dirac mass terms involving the "wrong Higgs" field can arise either at tree level due to hard supersymmetry breaking fermion Yukawa couplings, or at one-loop due to nonanalytic or "nonholomorphic" soft supersymmetry breaking trilinear scalar couplings. As both of these operators are naturally suppressed in generic models of supersymmetry breaking, the resulting neutrino masses are naturally in the sub-eV range. The neutrino magnetic and electric dipole moments resulting from the radiative mechanism also vanish at one-loop order.Comment: 5 pages, 1 figure, references added, note added on effective superpotential mass terms generated upon U(1)' breakin

Thin accretion disk images of the black hole in symmergent gravity

In this paper, we study circular orbits, effective potential, and thin-accretion disk of a black hole in symmergent gravity within the Novikov-Thorne model in a way including the energy flux and temperature distribution. We determine bounds on symmergent gravity parameters and conclude that the accretion disk could be used as an astrophysical tool to probe symmergent gravity.Comment: 30 pages. Accepted for publication in Classical and Quantum Gravity, "Special Issue: Focus on Quantum Gravity Phenomenology in the Multi-Messenger Era: Challenges and Perspectives" (https://iopscience.iop.org/article/10.1088/1361-6382/aceb45). arXiv admin note: text overlap with arXiv:1901.05762, arXiv:2002.00589 by other author

Quasinormal modes and greybody factors of symmergent black hole

Symmergent gravity is an emergent gravity framework in which gravity emerges guided by gauge invariance, accompanied by new particles, and reconciled with quantum fields. In this paper, we perform a detailed study of the quasinormal modes and greybody factors of the black holes in symmergent gravity. Its relevant parameters are the quadratic curvature term $c_{\rm O}$ and the vacuum energy parameter $\alpha$. In our analyses, effects of the both parameters are investigated. Our findings suggest that, in both positive and negative direction, large $|c_{\rm O}|$ values of the parameter on the quasinormal modes parallel the Schwarzschild black hole. Moreover, the quasinormal model spectrum is found to be sensitive to the symmergent parameter $\alpha$. We contrast the asymptotic iteration and WKB methods in regard to their predictions for the quasinormal frequencies, and find that they differ (agree) slightly at small (large) multipole moments. We analyze time-domain profiles of the perturbations, and determine the greybody factor of the symmergent black hole in the WKB regime. The symmergent parameter $\alpha$ and the quadratic curvature term $c_{\rm O}$ are shown to impact the greybody factors significantly. We provide also rigorous limits on greybody factors for scalar perturbations, and reaffirm the impact of model parameters.Comment: 23 pages, 16 figures. Published versio

Constraints on charged Symmergent black hole from shadow and lensing

In this paper, we report on exact charged black hole solutions in symmergent gravity with Maxwell field. Symmergent gravity induces the gravitational constant $G$, quadratic curvature coefficient $c_{\rm O}$, and the vacuum energy $V_{\rm O}$ from the flat spacetime matter loops. In the limit in which all fields are degenerate in mass, the vacuum energy $V_{\rm O}$ can be expressed in terms of $G$ and $c_{\rm O}$. We parametrize deviation from this limit by a parameter ${\hat \alpha}$ such that the black hole spacetime is dS for ${\hat \alpha} 1$. In our analysis, we study horizon formation, shadow cast and gravitational lensing as functions of the black hole charge, and find that there is an upper bound on the charge. At relatively low values of charge, applicable to astronomical black holes, we determine constraints on $c_{\rm O}$ and ${\hat \alpha}$ using the EHT data from Sgr. A* and M87*. We apply these constraints to reveal how the shadow radius behaves as the observer distance $r_O$ varies. It is revealed that black hole charge directly influences the shadow silhouette, but the symmergent parameters have a tenuous effect. We also explored the weak field regime by using the Gauss-Bonnet theorem to study the weak deflection angle caused by the M87* black hole. We have found that impact parameters comparable to the actual distance $D = 16.8$ Mpc show the potential detectability of such an angle through advanced astronomical telescopes. Overall, our results provide new insights into the behavior of charged black holes in the context of symmergent gravity and offer a new way to test these theories against observational data.Comment: 20 pages, 8 figures. Accepted for publication in Classical and Quantum Gravity, "Special Issue: Focus on Quantum Gravity Phenomenology in the Multi-Messenger Era: Challenges and Perspectives