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Dear Colleagues,

Supersymmetry provides a natural solution to the gauge hierarchy problem in the Standard Model (SM). In the supersymmetric SM, we can achieve gauge coupling unification, have a dark matter candidate, and break electroweak gauge symmetry through a radiative process. In particular, gauge coupling unification strongly suggests the Grand Unified Theory (GUT). Also, string theory is a promising candidate for quantum gravity, and the supersymmetric GUT can be constructed from string theory. Moreover, supersymmetry provides a natural framework for inflation. Prof. Dimitri Nanopoulos is one of the leading experts in the world on particle physics, supersymmetry, GUTs, string model building, and cosmology. For example, with various collaborators, he first studied the Higgs production at a hadronic collider via gluon fusion, proposed the flipped SU(5) model and constructed it from string theory, as well as proposed no-scale supergravity and studied its inflation.

This Special Issue is designed in honor of Prof. Dimitri Nanopoulos and to highlight the recent progress in particle physics and cosmology.

Prof. Dr. Jun-Jie Cao
Prof. Dr. Yungui Gong
Prof. Dr. Tianjun Li
Dr. Natsumi Nagata
Guest Editors

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Keywords

particle physics
supersymmetry
grand unified theory
string model building
cosmology

Published Papers (2 papers)

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Research

21 pages, 462 KiB

Open AccessArticle

Inflaton Decay in No-Scale Supergravity and Starobinsky-like Models

by Yohei Ema, Marcos A. G. Garcia, Wenqi Ke, Keith A. Olive and Sarunas Verner

Universe 2024, 10(6), 239; https://doi.org/10.3390/universe10060239 - 30 May 2024

Abstract

We consider the decay of the inflaton in Starobinsky-like models arising from either an

R + R^{2}

theory of gravity or

N = 1

no-scale supergravity models. If Standard Model matter is simply introduced to the

R + R^{2}

theory, the [...] Read more.

We consider the decay of the inflaton in Starobinsky-like models arising from either an

R + R^{2}

theory of gravity or

N = 1

no-scale supergravity models. If Standard Model matter is simply introduced to the

R + R^{2}

theory, the inflaton (which appears when the theory is conformally transformed into the Einstein frame) couples to matter predominantly in Standard Model Higgs kinetic terms. This will typically lead to a reheating temperature of ∼3 ×

10^{9}

GeV. However, if the Standard Model Higgs is conformally coupled to curvature, the decay rate may be suppressed and vanishes for conformal coupling

ξ = 1 / 6

. Nevertheless, the inflaton decays through the conformal anomaly, leading to a reheating temperature of the order of

10^{8}

GeV. The Starobinsky potential may also arise in no-scale supergravity. In this case, the inflaton decays if there is a direct coupling of the inflaton to matter in the superpotential or to gauge fields through the gauge kinetic function. We also discuss the relation between the theories and demonstrate the correspondence between the no-scale models and the conformally coupled

R + R^{2}

theory (with

ξ = 1 / 6

). Full article

(This article belongs to the Special Issue Particle Physics and Cosmology: A Themed Issue in Honor of Professor Dimitri Nanopoulos)

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13 pages, 767 KiB

Open AccessArticle

Revisiting a Realistic Intersecting D6-Brane with Modified Soft SUSY Terms

by Imtiaz Khan, Waqas Ahmed, Tianjun Li and Shabbar Raza

Universe 2024, 10(4), 176; https://doi.org/10.3390/universe10040176 - 11 Apr 2024

Viewed by 644

Abstract

Because there are a few typos in the supersymmetry-breaking sfermion masses and trilinear soft term, regarding the current Large Hadron Collider (LHC) and dark matter searches, we revisit a three-family Pati–Salam model based on intersecting D6-branes in Type IIA string theory on a [...] Read more.

T^{6} / (Z_{2} \times Z_{2})

orientifold with a realistic phenomenology. We study the viable parameter space and discuss the spectrum consistent with the current LHC Supersymmetry searches and the dark matter relic density bounds from the Planck 2018 data. For the gluinos and first two generations of sfermions, we observe that the gluino mass is in the range [2, 14] TeV, the squarks mass range is [2, 13] TeV and the sleptons mass is in the range [1, 5] TeV. We achieve the cold dark matter relic density consistent with 5

σ

Planck 2018 bounds via A-funnel and coannihilation channels such as stop–neutralino, stau–neutralino, and chargino–neutralino. Except for a few chargino–neutralino coannihilation solutions, these solutions satisfy current nucleon-neutralino spin-independent and spin-dependent scattering cross-sections and may be probed by future dark matter searches. Full article

(This article belongs to the Special Issue Particle Physics and Cosmology: A Themed Issue in Honor of Professor Dimitri Nanopoulos)

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