WHY IS THE HIDDEN SECTOR INVISIBLE?

2000 ◽  
Vol 15 (35) ◽  
pp. 2131-2137 ◽  
Author(s):  
M. D. POLLOCK
Keyword(s):  
Degrees Of Freedom ◽  
Coupling Parameter ◽  
Vacuum State ◽  
Fine Tuning ◽  
Gauge Mediation ◽  
Superstring Theory ◽  
Thermodynamical Equilibrium ◽  
Hidden Sector ◽  
Axion Field ◽  
Model Independent

The hidden sector of the E8×E′8 heterotic superstring theory of Gross et al. can in principle contain additional "shadow" matter, interacting only gravitationally with the real world in which we live. The SU (3)′ C × SU (2)′ L × U (1)′ Y shadow configuration symmetric to the standard model has been ruled out by Kolb et al. from nucleosynthesis arguments, combined with the existence of three light neutrinos. In the absence of inflation and of entropy enhancement by the out-of-equilibrium decay of an unstable particle, the same exclusion applies to the unbroken E′8 hidden gauge group, assuming thermodynamical equilibrium with the observable sector E6 group, and consequently all breaking chains E′8→ G1×G2×⋯, since they can only reduce the effective number of four-dimensional degrees of freedom g eff . The hidden sector would then appear to be in its vacuum state, which implies the absence of all condensates as well, if their potentials are positive semi-definite. In this case, and if there is no anomalous U(1) symmetry in the observable sector, the QCD axion is the model-independent axion, whose decay constant [Formula: see text] (where [Formula: see text] is the strong-interaction coupling parameter) requires a fine-tuning of the initial value of this axion field to ai/fa≲3×10-3, in order not to overclose the Universe today, supersymmetry being broken by gauge mediation. Vice versa, if ai/fa~1, then hidden-sector gaugino condensation is necessary for there to be a sufficiently massive gravitino, whose decay can increase the entropy. Astronomical microlensing observations may help to discriminate between these two cases.

ON THE RELAXATION OF SUPERSTRING AXIONS

2001 ◽  
Vol 16 (14) ◽  
pp. 2595-2604 ◽  
Author(s):  
M. D. POLLOCK
Keyword(s):  
Coupling Parameter ◽  
Relaxation Times ◽  
Free Fall ◽  
Galactic Centre ◽  
Boson Stars ◽  
Superstring Theory ◽  
Relaxation Theory ◽  
Dimensionless Constant ◽  
Model Independent ◽  
Age Of The Universe

The theoretical existence of oscillating boson stars consisting of a real scalar field, stable to radial perturbations, has been proven by Seidel and Suen. For the QCD axion of the heterotic superstring theory, this implies a mini-star of mass [Formula: see text], where λ≡ fa′/fa is the ratio of the decay constants of the second and model-independent axions, which, for a suitable value in the range 1≲λ≲10, can explain the astronomical microlensing observations towards the Galactic centre and the Large and Small Magellanic Clouds. Here, we apply the non-linear relaxation theory developed by Tkachev to show that the condition τ f <τ r <τ0 for the formation of such an object, where τ f , τ r and τ0 are the free-fall and relaxation times and the age of the Universe, respectively, leads to the condition [Formula: see text], where [Formula: see text] is the strong-interaction coupling parameter and C is a dimensionless constant defined below. From this, we argue, considering the approximations involved, that the star does condense.

ON THE RELAXATION OF SUPERSTRING AXION MINI-CLUSTERS

2003 ◽  
Vol 18 (14) ◽  
pp. 947-953 ◽  
Author(s):  
M. D. POLLOCK
Keyword(s):  
Decay Constant ◽  
Galactic Center ◽  
Coupling Parameter ◽  
Relaxation Mechanism ◽  
Superstring Theory ◽  
Decay Constants ◽  
Model Independent ◽  
Age Of The Universe ◽  
Axion Decay ◽  
The Universe

The cosmological axion theory leads to the prediction of axionic mini-clusters of mass M ~ 10-9M⊙, which form at the time t e of equipartition of matter and radiation. By applying the two-body relaxation formula of Spitzer and Hart, we show, for the heterotic superstring theory of Gross et al., that these mini-clusters, considered as point masses, themselves cluster into axion mini-stars of mass [Formula: see text] within the age of the Universe t0 only if they are located within a distance R ~ 0.1 pc of the Galactic Center. Here, λ ≡ fB/fA is the ratio of the second to model-independent axion decay constants, assuming the QCD decay constant to be in the range [Formula: see text], and [Formula: see text] is the strong-interaction coupling parameter. Thus, if axion mini-stars are to explain the microlensing observations by the EROS and MACHO groups towards the Galactic Bulge and the Large and Small Magellanic Clouds, then a collisionless relaxation mechanism is required, as proposed by Seidel and Suen (essentially the violent relaxation of Lynden–Bell), or the four-axion self-interaction effect considered by Tkachev.

scholarly journals Low fine-tuning in Yukawa-deflected gauge mediation

2017 ◽  
Vol 95 (9) ◽  
Author(s):  
Waqas Ahmed ◽  
Lorenzo Calibbi ◽  
Tianjun Li ◽  
Azar Mustafayev ◽  
Shabbar Raza
Keyword(s):  
Fine Tuning ◽  
Gauge Mediation

scholarly journals The art of the state

2018 ◽  
Vol 27 (11) ◽  
pp. 1843007 ◽  
Author(s):  
Christopher J. Fewster
Keyword(s):  
Infinite Family ◽  
Vacuum State ◽  
Natural Conditions ◽  
Spacetime Geometry ◽  
High Energies ◽  
Hyperbolic Spacetime ◽  
Hadamard Condition ◽  
Free Scalar ◽  
Model Independent ◽  
Hadamard States

Quantum field theory (QFT) on curved spacetimes lacks an obvious distinguished vacuum state. We review a recent no-go theorem that establishes the impossibility of finding a preferred state in each globally hyperbolic spacetime, subject to certain natural conditions. The result applies in particular to the free scalar field, but the proof is model-independent and therefore of wider applicability. In addition, we critically examine the recently proposed “SJ states”, that are determined by the spacetime geometry alone, but which fail to be Hadamard in general. We describe a modified construction that can yield an infinite family of Hadamard states, and also explain recent results that motivate the Hadamard condition without direct reference to ultra-high energies or ultra-short distance structure.

scholarly journals Model-independent indirect detection constraints on hidden sector dark matter

2016 ◽  
Vol 2016 (06) ◽  
pp. 024-024 ◽  
Author(s):  
Gilly Elor ◽  
Nicholas L. Rodd ◽  
Tracy R. Slatyer ◽  
Wei Xue
Keyword(s):  
Dark Matter ◽  
Indirect Detection ◽  
Hidden Sector ◽  
Model Independent

scholarly journals Axion hilltops, Kahler modulus quintessence and the swampland criteria

2019 ◽  
Vol 34 (28) ◽  
pp. 1950164 ◽  
Author(s):  
Maxim Emelin ◽  
Radu Tatar
Keyword(s):  
Degrees Of Freedom ◽  
Initial Conditions ◽  
Effective Field ◽  
Fine Tuning ◽  
De Sitter ◽  
Moduli Stabilization ◽  
Nonperturbative Effect ◽  
Initial Conditions Problem ◽  
Field Excursion ◽  
Hubble Time

We study the interplay among extrema of axion potentials, Kahler moduli stabilization and the swampland criteria. We argue that moving away from the minima of nonperturbatively generated axion potentials can lead to a runaway behavior of moduli that govern the couplings in the effective field theory. The proper inclusion of these degrees of freedom resolves the conflict between periodic axion potentials and the gradient de Sitter criterion, without the need to invoke the refined de Sitter criterion. We investigate the possibility of including this runaway direction as a model of quintessence that satisfies the swampland criteria. Using a single nonperturbative effect, the maximum along the axion direction provides such a runaway direction, which is unstable in the axion directions, sensitive to initial conditions and too steep to allow for a Hubble time of expansion without violating the field excursion criterion. Adding a second nonperturbative effect generates a saddle point in the potential satisfying the refined de Sitter criterion, which solves the steepness problem and improves the initial conditions problem although some fine-tuning remains required.

scholarly journals Focus point gauge mediation without a severe fine-tuning

2018 ◽  
Vol 2018 (10) ◽  
Author(s):  
Tsutomu T. Yanagida ◽  
Norimi Yokozaki
Keyword(s):  
Fine Tuning ◽  
Gauge Mediation ◽  
Focus Point

scholarly journals Hidden sector gaugino condensation and the model-independent axion

1998 ◽  
Vol 437 (3-4) ◽  
pp. 325-330 ◽  
Author(s):  
Howard Georgi ◽  
Jihn E. Kim ◽  
Hans-Peter Nilles
Keyword(s):  
Hidden Sector ◽  
Model Independent

scholarly journals A String-Inspired Ansatz for Quark Masses and Mixing

1997 ◽  
Vol 12 (08) ◽  
pp. 561-571 ◽  
Author(s):  
Tatsuo Kobayashi ◽  
Zhi-Zhong Xing
Keyword(s):  
Quark Mass ◽  
Fine Tuning ◽  
Superstring Theory ◽  
Quark Masses ◽  
Gauge Symmetries ◽  
Down Quark ◽  
Mass Matrices ◽  
Renormalization Group Equations ◽  
Flavor Mixing ◽  
Good Agreement

We propose a simple but realistic pattern of quark mass matrices at the string scale, which can be derived from orbifold models of superstring theory with no use of gauge symmetries. This pattern is left–right symmetric and preserves the structural parallelism between up and down quark sectors. Its phenomenological consequences on flavor mixing and CP-violation are confronted with current experiments at the weak scale by using the renormalization group equations in the framework of minimal supersymmetric standard model. We find that good agreement is achievable without fine-tuning.

QUANTUM GRAVITATIONAL EFFECTS AND THE COMPACTIFICATION SCALE IN THE HETEROTIC SUPERSTRING THEORY

1999 ◽  
Vol 14 (01) ◽  
pp. 119-127 ◽  
Author(s):  
M. D. POLLOCK
Keyword(s):  
Black Holes ◽  
Wormhole Solution ◽  
Superstring Theory ◽  
Gravitational Effects ◽  
Parity Symmetry ◽  
Anomalous Term ◽  
Higher Derivative ◽  
Euclidean Action ◽  
Model Independent ◽  
Virtual Black Holes

It is known that quantum gravitational effects due to virtual black holes and wormholes can exert an important influence by violating global symmetries. These processes have recently been investigated by Kallosh et al., who found, for the heterotic superstring theory, that there is a sufficient suppression of deleterious effects via the Euclidean action S E from the presence of higher-derivative terms occurring as a topological invariant, the Euler characteristic χ, regardless of the precise details of the underlying wormhole solution. Here, we consider this result further, arguing, in the absence of inflation, that there are no large wormholes in the heterotic superstring theory for which the wormhole action per se is large enough, topological suppression being the only possibility. The model-independent superstring axion may be susceptible to these corrections, because, as shown by Witten, it possesses a non-linearly realized, global U(1) symmetry, being a real scalar field coupled to the anomalous term [Formula: see text] from the outset, and they are relevant to the R-parity symmetry. Allowing for the unknown effect of the black holes, however, we conjecture that these quantum gravitational effects produce no observable consequences.

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