相关论文: Optical Unification

Recently J. Giedt discussed a mechanism, entitled optical unification, whereby string scale unification is facilitated via exotic matter with intermediate scale mass. This mechanism guarantees that a virtual MSSM unification below the…

The lower limit to string coupling unification in weakly coupled heterotic strings was shown by Kaplunovsky to be around Lambda_H ~ 5 x 10^{17} GeV. In contrast, under the scenario of an intermediate scale desert, the SU(3)_C x SU(2)_L x…

In the context of the minimal supersymmetric standard model (MSSM), we discuss the introduction of exotic matter below the string scale $M_X$ in order to achieve gauge unification at $M_X$ (a constraint of a large class of string models).…

Motivated by the fact that the string scale can be many orders of magnitude lower than the Planck mass, we investigate the required modifications in the MSSM $\beta$--functions in order to achieve intermediate ($10^{10-13}$GeV) scale…

Four-dimensional string theories predict in general the existence of light exotic particles with fractional electric charges. Such particles could escape present observations if they are confined by a gauge group of the "hidden" sector into…

One of the drawbacks of conventional grand unification scenarios has been that the unification scale is too high to permit direct exploration. In this paper, we show that the unification scale can be significantly lowered (perhaps even to…

We use a new approach to study string scale gauge coupling unification systematically, allowing both the possibility of non-canonical U(1)_Y normalization and the existence of vector-like particles whose quantum numbers are the same as…

We argue that moduli in the adjoint representation of the standard- model gauge group are a natural feature of superstring models, and that they can account for the apparent discrepancy between the string and unification scales.

A long-standing problem in string phenomenology has been the fact that the string unification scale disagrees with the GUT scale obtained by extrapolating low-energy data within the framework of the minimal supersymmetric standard model…

I argue that in open-string theory with hierarchically small (or large) extra dimensions, gauge groups can unify naturally with logarithmically-running coupling constants at the high Kaluza-Klein (or string-winding) scale. This opens up the…

We study gauge coupling unification in the presence of extra dimensions compactified at a few TeV. Achieving unification requires a large number of gauge boson Kaluza-Klein excitations lighter than the string scale, such that the…

The idea of grand unification in a minimal supersymmetric SU(5)xSU(5) framework is revisited. It is shown that the unification of gauge couplings into a unique coupling constant can be achieved at a high-energy scale compatible with proton…

Gauge coupling unification is studied in the MSSM with non-universal soft supersymmetry breaking terms. If gaugino masses are sufficiently smaller than scalar soft masses and the scalar soft masses have also certain types of…

The recent conjecture of possible equivalence between the string scale $M_S$ and the minimal supersymmetric standard model unification scale M_U ~ 2.5 x 10^{16} GeV is considered in the context of string models. This conjecture suggests…

The significant heavy threshold effect is found in the supersymmetric SU(5) model with two adjoint scalars, one of which is interpreted as a massive string mode decoupled from the lower-energy particle spectra. This threshold related with…

We present a new scenario for gauge coupling unification in flipped SU(5) string models, which identifies the $M_{32}$ scale of SU(3) and SU(2) unification with the empirical $M_{\rm LEP}\sim10^{15-16}$~GeV scale, and the $M_{51}$ scale of…

We study the unification scale and gauge coupling constant in 4D string theory. We show that the fine structure constant is determined by the dimension of the hidden gauge group and only $SU(6)$ and $SO(9)$ are consistent with minimal…

We study the gauge coupling unification of the minimal supersymmetric standard model with non-universal soft scalar and gaugino masses. The unification scale of the gauge couplings is estimated for non-universal cases. It is sensitive to…

Utilizing the idea of extra large dimensions, it has been suggested that the gauge and gravity couplings unification can happen at a scale as low as 1 TeV. In this paper, we explore this phenomenological possibility within string theory. In…

We show that large string threshold corrections can reconcile the string and MSSM unification scales in fermionic strings. This requires at least three moduli with large VEVs which are different from each other and MSSM states arising in an…