Classification of Flipped SU(5) Heterotic-String Vacua

We extend the classification of the free fermionic heterotic-string vacua to models in which the SO(10) GUT symmetry at the string scale is broken to the flipped SU(5) subgroup. In our classification method, the set of basis vectors defined by the boundary conditions which are assigned to the free fermions is fixed and the enumeration of the string vacua is obtained in terms of the Generalised GSO (GGSO) projection coefficients entering the one-loop partition function. We derive algebraic expressions for the GGSO projections for all the physical states appearing in the sectors generated by the set of basis vectors. This enables the analysis of the entire string spectrum to be programmed in to a computer code therefore, we performed a statistical sampling in the space of 2^{44} (approximately 10^{13}) flipped $SU(5)$ vacua and scanned up to 10^{12} GGSO configurations. For that purpose, two independent codes were developed based on JAVA and FORTRAN95. All the results presented here are confirmed by the two independent routines. Contrary to the corresponding Pati-Salam classification, we do not find exophobic flipped SU(5) vacua with an odd number of generations. We study the structure of exotic states appearing in the three generation models that additionally contain a viable Higgs spectrum. Moreover, we demonstrate the existence of models in which all the exotic states are confined by a hidden sector non-Abelian gauge symmetry as well as models that may admit the racetrack mechanism.Comment: Minor changes (Version 2) - 51 pages - 3 figures - Added acknowledgement

Non-Tachyonic Semi-Realistic Non-Supersymmetric Heterotic String Vacua

The heterotic--string models in the free fermionic formulation gave rise to some of the most realistic string models to date, which possess N=1 spacetime supersymmetry. Lack of evidence for supersymmetry at the LHC instigated recent interest in non-supersymmetric heterotic-string vacua. We explore what may be learned in this context from the quasi--realistic free fermionic models. We show that constructions with a low number of families give rise to proliferation of a priori tachyon producing sectors, compared to the non--realistic examples, which typically may contain only one such sector. The reason being that in the realistic cases the internal six dimensional space is fragmented into smaller units. We present one example of a quasi--realistic, non--supersymmetric, non--tachyonic, heterotic--string vacuum and compare the structure of its massless spectrum to the corresponding supersymmetric vacuum. While in some sectors supersymmetry is broken explicitly, i.e. the bosonic and fermionic sectors produce massless and massive states, other sectors, and in particular those leading to the chiral families, continue to exhibit fermi-bose degeneracy. In these sectors the massless spectrum, as compared to the supersymmetric cases, will only differ in some local or global U(1) charges. We discuss the conditions for obtaining $n_b=n_f$ at the massless level in these models. Our example model contains an anomalous U(1) symmetry, which generates a tadpole diagram at one loop-order in string perturbation theory. We speculate that this tadpole diagram may cancel the corresponding diagram generated by the one-loop non-vanishing vacuum energy and that in this respect the supersymmetric and non-supersymmetric vacua should be regarded on equal footing. Finally we discuss vacua that contain two supersymmetry generating sectors.Comment: 31 pages. 10 tables. Minor corrections. Tables are amended. Published versio

Classification of SU(4) X SU(2) X U(1) Heterotic-String Models

The free fermionic construction of the heterotic string in four dimensions produced a large space of three generation models with the underlying $SO(10)$ embedding of the Standard Model states. The $SO(10)$ symmetry is broken to a subgroup directly at the string scale. Over the past few years free fermionic models with the Pati-Salam and flipped $SU(5)$ subgroups have been classified. In this paper we extend this classification program to models in which the $SO(10)$ symmetry is broken at the string level to the $SU(4)\times SU(2)_L\times U(1)_R$ (SU421) subgroup. The subspace of free fermionic models that we consider corresponds to symmetric ${\mathbb{Z}}_2 \times {\mathbb{Z}}_2$ orbifolds. We provide a general argument that shows that this class of SU421 free fermionic models cannot produce viable three generation models.Comment: Publication Version (Notes: 16 Pages & References added

Classifications of the free fermionic heterotic string vacua

The existence of discrete properties is shown in the landscape of the Free-Fermionic Heterotic-String vacua. These were discovered via the classification of the SO(10) GUT gauge group and its subgroups, such as, the Pati-Salam, the Flipped SU(5) and the SU(4)×SU(2)×U(1) models. The classification is carried out by fixing a set of basis vectors and then varying the GGSO projection coefficients entering the one-loop partition function. The analysis of the models is facilitated by deriving algebraic expressions for the GGSO projections to enable a computerised analysis of the entire String spectrum and the scanning of large spaces of vacua. The analysis reveals an abundance of 3 generation models with exophobic String vacua. This is observed with the SO(10) and the Pati-Salam models. Contrary to this, the Flipped SU(5) models contained no exophobic vacua with an odd number of generations. Moreover, it is also observed that the SU(4)×SU(2)×U(1) models are substantially more constrained and that no generations exist. The analysis of the SU(3)×U(1)×SU(2)×U(1) and the SU(3)×U(1)×SU(2)×SU(2) models are being examined, which is work in progress, that are expected to generate further interesting phenomenology

Right ventricular involvement in anterior myocardial infarction: a tissue Doppler-derived strain and strain rate study

OBJECTIVE: Strain and strain rate imaging is currently the most popular echocardiographic technique that reveals subclinical myocardial damage. There are currently no available data on this imaging method with regard to assessing right ventricular involvement in anterior myocardial infarction. Therefore, we aimed to evaluate right ventricular regional functions using a derived strain and strain rate imaging tissue Doppler method in patients who were successfully treated for their first anterior myocardial infarction. METHODS: The patient group was composed of 44 patients who had experienced their first anterior myocardial infarction and had undergone successful percutaneous coronary intervention. Twenty patients were selected for the control group. The right ventricular myocardial samplings were performed in three regions: the basal, mid, and apical segments of the lateral wall. The individual myocardial velocity, strain, and strain rate values of each basal, mid, and apical segment were obtained. RESULTS: The right ventricular myocardial velocities of the patient group were significantly decreased with respect to all three velocities in the control group. The strain and strain rate values of the right mid and apical ventricular segments in the patient group were significantly lower than those of the control group (excluding the right ventricular basal strain and strain rate). In addition, changes in the right ventricular mean strain and strain rate values were significant. CONCLUSION: Right ventricular involvement following anterior myocardial infarction can be assessed using tissue Doppler based strain and strain rat

Assessment of the left atrial volume index and plasma NT-proANP level in patients with acute ST-elevation myocardial infarction

OBJECTIVES: Acute ST-elevation myocardial infarction is associated with ventricular dysfunction due to ischemia-induced progressive myocardial damage. The decrease in ventricular compliance causes left atrial dilatation and stretching of the atrial myocardium, which are the main stimuli for the secretion of atrial natriuretic peptide. The aim of this study was to evaluate left atrial dimensions and atrial natriuretic peptide levels in patients early after their first acute ST-elevation myocardial infarction and assess the probable interaction between coronary lesions and these measurements. METHODS: A total of 110 patients with acute myocardial infarction and 50 controls were studied. Plasma atrial natriuretic peptide was measured at admission. Left ventricular function, diameter, and volume index were evaluated using transthoracic echocardiography. Gensini and vessel scores of the patients who underwent coronary angiography were calculated. RESULTS: Plasma atrial natriuretic peptide in the patients with myocardial infarction was increased compared with that in controls (3.90±3.75 vs. 1.35±0.72 nmol/L,

Synthesis, characterization, cytotoxicity evaluation and physicochemical properties of some novel N4-substituted aminobenzenesulfonamides

Several N4-substituted aminobenzenesulfonamides derivatives have been synthesized and structural analyses have been carried out using FT-IR, UV-Vis, 1H and 13C NMR, LC-MS-MS and elemental analyses. Photoluminescence and physicochemical properties have also been conducted. Two 4-aminobenzenesulfonamides have been treated with 2-bromopropionyl bromide in pyridine to give their respective bromo substituted aminobenzenesulfonamides as intermediates. Subsequent reactions with morpholino-, thiomorpholino- and piperazine amines have yielded novel aminobenzenesulfonamide derivatives. As it is well known that CA IX and CA XII enzymes play an active role in attacking various cancerous conditions, studies presented in this study target these enzymes with in vitro cytotoxicity studies being performed on the compounds synthesized. The target compounds have been found to be active against some cancerous cells, with mimimal effects on normal cells. The physicochemical data reveal interesting synergistic effects controlling cytotoxicities, where the lipophilicity and polarity combinations play important roles on the eventual observed cytotoxicities. Further, the electronegativity and availability of the electrons of the heteroatoms of the synthesized compounds appear to have an effect on cancer cell cytotoxicities

Synthesis, characterization, cytotoxicity evaluation and physicochemical properties of some novel N4-substituted aminobenzenesulfonamides

888-900Several N4-substituted aminobenzenesulfonamides derivatives have been synthesized and structural analyses have been carried out using FT-IR, UV-Vis, 1H and 13C NMR, LC-MS-MS and elemental analyses. Photoluminescence and physicochemical properties have also been conducted. Two 4-aminobenzenesulfonamides have been treated with 2-bromopropionyl bromide in pyridine to give their respective bromo substituted aminobenzenesulfonamides as intermediates. Subsequent reactions with morpholino-, thiomorpholino- and piperazine amines have yielded novel aminobenzenesulfonamide derivatives. As it is well known that CA IX and CA XII enzymes play an active role in attacking various cancerous conditions, studies presented in this study target these enzymes with in vitro cytotoxicity studies being performed on the compounds synthesized. The target compounds have been found to be active against some cancerous cells, with mimimal effects on normal cells. The physicochemical data reveal interesting synergistic effects controlling cytotoxicities, where the lipophilicity and polarity combinations play important roles on the eventual observed cytotoxicities. Further, the electronegativity and availability of the electrons of the heteroatoms of the synthesized compounds appear to have an effect on cancer cell cytotoxicities