scholarly journals Tachyon condensation in magnetic compactifications

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Wilfried Buchmuller ◽  
Emilian Dudas ◽  
Yoshiyuki Tatsuta
Keyword(s):  
Ground State ◽  
Particle Physics ◽  
Tachyon Condensation ◽  
Quantum Corrections ◽  
Type I ◽  
Local Minima ◽  
Superstring Theory ◽  
Dual Version ◽  
Brane Models ◽  
Kaluza Klein

Abstract Intersecting D-brane models and their T-dual magnetic compactifications provide an attractive framework for particle physics, allowing for chiral fermions and supersymmetry breaking. Generically, magnetic compactifications have tachyons that are usually removed by Wilson lines. However, quantum corrections prevent local minima for Wilson lines. We therefore study tachyon condensation in the simplest case, the magnetic compactification of type I string theory on a torus to eight dimensions. We find that tachyon condensation restores supersymmetry, which is broken by the magnetic flux, and we compute the Kaluza-Klein mass spectrum. The gauge group SO(32) is broken to USp(16). We give arguments that the vacuum reached by tachyon condensation corresponds to the unique 8d superstring theory already known in the literature, with discrete Bab background or, in the T-dual version, the type IIB orientifold with three O7−-planes, one O7+-plane and eight D7-branes coincident with the O7+-plane. The ground state after tachyon condensation is supersymmetric and has no chiral fermions.

scholarly journals Relaxing cosmological neutrino mass bounds with unstable neutrinos

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Miguel Escudero ◽  
Jacobo Lopez-Pavon ◽  
Nuria Rius ◽  
Stefan Sandner
Keyword(s):  
Neutrino Mass ◽  
Particle Physics ◽  
Goldstone Boson ◽  
Mass Scale ◽  
Simple Extension ◽  
Type I ◽  
Mass Generation ◽  
Age Of The Universe ◽  
Neutrino Mass Models ◽  
The Right

Abstract At present, cosmological observations set the most stringent bound on the neutrino mass scale. Within the standard cosmological model (ΛCDM), the Planck collaboration reports ∑mv< 0.12 eV at 95 % CL. This bound, taken at face value, excludes many neutrino mass models. However, unstable neutrinos, with lifetimes shorter than the age of the universe τν ≲ tU, represent a particle physics avenue to relax this constraint. Motivated by this fact, we present a taxonomy of neutrino decay modes, categorizing them in terms of particle content and final decay products. Taking into account the relevant phenomenological bounds, our analysis shows that 2-body decaying neutrinos into BSM particles are a promising option to relax cosmological neutrino mass bounds. We then build a simple extension of the type I seesaw scenario by adding one sterile state ν4 and a Goldstone boson ϕ, in which νi→ ν4ϕ decays can loosen the neutrino mass bounds up to ∑mv ∼ 1 eV, without spoiling the light neutrino mass generation mechanism. Remarkably, this is possible for a large range of the right-handed neutrino masses, from the electroweak up to the GUT scale. We successfully implement this idea in the context of minimal neutrino mass models based on a U(1)μ−τ flavor symmetry, which are otherwise in tension with the current bound on ∑mv.

Review of inflationary cosmology via quantum corrections in M-theory

2019 ◽  
Vol 34 (33) ◽  
pp. 1930016
Author(s):  
Kazuho Hiraga ◽  
Yoshifumi Hyakutake
Keyword(s):  
Scalar Curvature ◽  
Early Universe ◽  
Quantum Effect ◽  
Quantum Corrections ◽  
Inflationary Cosmology ◽  
Superstring Theory ◽  
Inflationary Scenario ◽  
Starobinsky Model ◽  
M Theory

In this paper, we review inflationary cosmology in M-theory with quantum corrections. In old days the inflation was proposed as a resolution to the cosmological problems, and nowadays models of the inflation are severely restricted by the observations. Among them, the predictions of the Starobinsky model, which contains scalar curvature squared term, is consistent with the observations. The higher curvature terms will come from quantum effect of the gravity, and it is natural to ask its origin in superstring theory or M-theory. We investigate inflationary solution in the M-theory with higher curvature terms. We show that higher curvature terms induce an exponentially expanding solution in the early universe, and the inflation naturally ends when the corrections are suppressed. We also discuss that the ambiguity of the higher curvature terms do not affect the inflationary scenario in the M-theory.

On the Vanishing of the Cosmological Vacuum Energy

1997 ◽  
Vol 12 (16) ◽  
pp. 1127-1130 ◽  
Author(s):  
M. D. Pollock
Keyword(s):  
Wave Function ◽  
Schrödinger Equation ◽  
Ground State ◽  
Schrodinger Equation ◽  
Vacuum Energy ◽  
Ground State Solution ◽  
Space Time ◽  
State Solution ◽  
Superstring Theory ◽  
The Universe

By demanding the existence of a globally invariant ground-state solution of the Wheeler–De Witt equation (Schrödinger equation) for the wave function of the Universe Ψ, obtained from the heterotic superstring theory, in the four-dimensional Friedmann space-time, we prove that the cosmological vacuum energy has to be zero.

scholarly journals Rigour and rigidity: Systematics on particle physics D6-brane models on ℤ2× ℤ6

2014 ◽  
Vol 62 (11-12) ◽  
pp. 981-1040 ◽  
Author(s):  
J. Ecker ◽  
G. Honecker ◽  
W. Staessens
Keyword(s):  
Particle Physics ◽  
Brane Models

scholarly journals TEV NEUTRINO PHYSICS AT THE LARGE HADRON COLLIDER

2009 ◽  
Vol 24 (18n19) ◽  
pp. 3286-3296 ◽  
Author(s):  
ZHI-ZHONG XING
Keyword(s):  
Neutrino Physics ◽  
Large Hadron Collider ◽  
Particle Physics ◽  
Degrees Of Freedom ◽  
Neutrino Oscillations ◽  
Hadron Collider ◽  
Higgs Bosons ◽  
Type I ◽  
Seesaw Mechanism ◽  
Majorana Neutrinos

I argue that TeV neutrino physics might become an exciting frontier of particle physics in the era of the Large Hadron Collider (LHC). The origin of non-zero but tiny masses of three known neutrinos is probably related to the existence of some heavy degrees of freedom, such as heavy Majorana neutrinos or heavy Higgs bosons, via a TeV-scale seesaw mechanism. I take a few examples to illustrate how to get a balance between theoretical naturalness and experimental testability of TeV seesaws. Besides possible collider signatures at the LHC, new and non-unitary CP-violating effects are also expected to show up in neutrino oscillations for type-I, type-(I+II) and type-III seesaws at the TeV scale.

FILLING LANDAU LEVELS: FERMI SEA GROUND STATE ENERGY, COMPETING INTERACTIONS AND MARGINAL DISPERSIONS IN GENERALIZED FLUX PHASES

1992 ◽  
Vol 06 (05n06) ◽  
pp. 563-583
Author(s):  
Benoit Douçot ◽  
Franco Nori ◽  
R. Rammal
Keyword(s):  
Kinetic Energy ◽  
Landau Level ◽  
Ground State Energy ◽  
Ground State ◽  
State Energy ◽  
Level Structure ◽  
Minimum Energy ◽  
Landau Levels ◽  
Integer Number ◽  
Local Minima

ABSTRACT: We review recent studies on the energetics of fermions confined to a two dimensional square lattice, and the relations of these results to mean-field approaches to the t−J model. Our goal has been to compute the kinetic energy of the Fermi sea of the spinless fermions for any value of the (1) fermion concentration, (2) magnetic flux, and (3) frustration. For the unfrustrated case, we confirm that the ground state energy, χ(Φ), is a minimum for Φ=π(1−δ), which corresponds to one flux quantum per spinless fermion. We then proceed to do a systematic study of frustration effects, coming from longer range couplings, which modify the picture obtained for the unfrustrated case. The frustrating influence of the kinetic energy of the holes (e.g., by breaking magnetic bonds and suppressing the long-range order present in the undoped systems) is the main focus of this work. We find that, in general, E(Φ) always exhibits cusp-like minima which position moves linearly as a function of the fermion density x. Frustration can induce a competition between different local minima. By first considering the local minima for one particle only, we can understand most of the qualitative features of E(Φ). These local minima occur at simple rational fractions of Φ0, and when the flux slightly deviates from these values a one-particle Landau level structure develops. It is precisely such a spectrum that generates a family of cusps that “move away” from the original flux value as x is increased. Every cusp corresponds to an integer number of filled Landau levels, and the minimum energy cusp corresponds to the one level case. Furthermore, we use perturbation theory, valid for low fermion density x, in order to analyze quantitatively the behavior of the cusp-like energy minima; which originate from the Landau level structure when the flux is close to a rational value. If the flux is slightly away from a given rational value [Formula: see text] each of the q subbands generates a secondary Landau level structure. We have derived a t2−t3 phase diagram indicating regions of similar behavior (i.e., adiabatic continuations can be performed with each region, preserving the E(Φ) structure) and the boundaries between them. We have studied several points belonging to those boundaries and found that anomalous behavior, (e.g., cancelation of the k2 term in the dispersion relation) induced by frustration, can occur.

scholarly journals INTERSECTING BRANE WORLD FROM TYPE I COMPACTIFICATION

2007 ◽  
Vol 22 (19) ◽  
pp. 3169-3200 ◽  
Author(s):  
KANG-SIN CHOI
Keyword(s):  
Symmetry Breaking ◽  
Gauge Coupling ◽  
Brane World ◽  
Type I ◽  
Weak Mixing Angle ◽  
Weak Mixing ◽  
Mixing Angle ◽  
String Compactifications ◽  
Quantum Numbers ◽  
Brane Models

We elaborate that general intersecting brane models on orbifolds are obtained from type I string compactifications and their T-duals. Symmetry breaking and restoration occur via recombination and parallel separation of branes, preserving supersymmetry. The Ramond–Ramond tadpole cancellation and the toron quantization constrain the spectrum as a branching of the adjoints of SO(32), up to orbifold projections. Since the recombination changes the gauge coupling, the single gauge coupling of type I could give rise to different coupling below the unification scale. This is due to the nonlocal properties of the Dirac–Born–Infeld action. The desirable weak mixing angle sin 2θW = 3/8 is naturally explained by embedding the quantum numbers to those of SO(10).

scholarly journals Multiple solutions in supersymmetry and the Higgs

2015 ◽  
Vol 373 (2032) ◽  
pp. 20140035 ◽  
Author(s):  
Ben C. Allanach
Keyword(s):  
Supersymmetry Breaking ◽  
Particle Physics ◽  
Multiple Solutions ◽  
Higgs Mass ◽  
Hadron Collider ◽  
Quantum Corrections ◽  
Beyond The Standard Model ◽  
Universal Model ◽  
The Standard Model ◽  
Supersymmetric Particles

Weak-scale supersymmetry is a well-motivated, if speculative, theory beyond the Standard Model of particle physics. It solves the thorny issue of the Higgs mass, namely: how can it be stable to quantum corrections, when they are expected to be 10 15 times bigger than its mass? The experimental signal of the theory is the production and measurement of supersymmetric particles in the Large Hadron Collider (LHC) experiments. No such particles have been seen to date, but hopes are high for the impending run in 2015. Searches for supersymmetric particles can be difficult to interpret. Here, we shall discuss the fact that, even given a well-defined model of supersymmetry breaking with few parameters, there can be multiple solutions. These multiple solutions are physically different and could potentially mean that points in parameter space have been ruled out by interpretations of LHC data when they should not have been. We shall review the multiple solutions and illustrate their existence in a universal model of supersymmetry breaking.

TYPE I SUPERSTRING THEORY IN THE FORM OF OPEN TYPE IIB ONE WITH APPROPRIATE CHOICE OF BOUNDARY CONDITIONS

2009 ◽  
Vol 24 (15) ◽  
pp. 2857-2865
Author(s):  
BOJAN NIKOLIĆ ◽  
BRANISLAV SAZDOVIĆ
Keyword(s):  
Boundary Conditions ◽  
Type I ◽  
World Sheet ◽  
Superstring Theory ◽  
Open Type

We improve relation between type IIB and type I superstring theory. In fact we obtain type I theory as type IIB on the solution of appropriately chosen boundary conditions. We find that type I theory, which is symmetric under world-sheet parity transformation Ω : σ → - σ, beside Ω even fields of the type IIB theory, contains squares of Ω odd fields.

scholarly journals NONPERTURBATIVE APPROACH TO YANG–MILLS THERMODYNAMICS

2005 ◽  
Vol 20 (18) ◽  
pp. 4123-4216 ◽  
Author(s):  
RALF HOFMANN
Keyword(s):  
State Physics ◽  
Phase Transitions ◽  
Density Of States ◽  
Ground State ◽  
Particle Physics ◽  
Scalar Fields ◽  
Temperature Evolution ◽  
Two Phase ◽  
Yang Mills ◽  
Massive Spin

An analytical and nonperturbative approach to SU(2) and SU(3) Yang–Mills thermodynamics is developed and applied. Each theory comes in three phases: A deconfining, a preconfining, and a confining one. We show how macroscopic and inert scalar fields emerge in each phase and how they determine the ground-state physics and the properties of the excitations. While the excitations in the deconfining and preconfining phases are massless or massive gauge modes the excitations in the confining phase are massless or massive spin-1/2 fermions. The nature of the two phase transitions is investigated for each theory. We compute the temperature evolution of thermodynamical quantities in the deconfining and preconfining phase and estimate the density of states in the confining phase. Some implications for particle physics and cosmology are discussed.

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