arXiv subjects

Christos Kokorelis

Publications and source records attributed to Christos Kokorelis.

At least 19 recordsLinked to original sources

arXiv2022

Quantization in Cartesian coordinates and the Hofer metric

P.A.M. Dirac had stated that the Cartesian coordinates are uniquely suited for expressing the canonical commutation relations in a simple form. By contrast, expressing these commutation relations in any other coordinate system is more complicated and less obvious. The question that we address in this work, is the reason why this is true. We claim that this unique role of the Cartesian coordinates is a result of the existence and uniqueness of the Hofer metric on the space of canonical transformations of the phase space of the system getting quantized.

math-ph↗

arXiv2016

Gauge Unification from Split Supersymmetric String Models

We discuss the unification of gauge coupling constants in non-supersymmetric open string vacua that possess the properties of Split Supersymmetry, namely the Standard Model with Higgsinos at low energies and where the Standard model spectrum is always accompanied by right handed neutrinos. These vacua achieve partial unification of two out of three (namely SU(3)$_c$, SU(2), U(1)) running gauge couplings, possess massive gauginos and light Higgsinos at low energies and also satisfy $sin^2θ_w (M_s) = 3/8$. These vacua are based on four dimensional orbifold $Z_3 \times Z_3$ compactifications of string IIA orientifolds with D6-branes intersecting at angles, where the (four dimensional) chiral fermions of the Standard Model appear as opens strings streching between the intersections of seven dimensional objects the so called D6-branes.

hep-ph↗

arXiv2016

The 750 GeV LHC diphoton excess from a baryon number conserving string model

We propose an explanation of the LHC data excess resonance of 750 GeV in the diphoton distribution using D-brane models, with gauged baryon number, which accommodate the Standard Model together with vector like exotics. We identify the 750 GeV scalar as either the sneutrino (${\tilde ν}_R$) or as an axion. Using a bottom-up approch, ${\tilde ν}_R$ is produced via gluon fusion when scalar (supersymmetric) partners of vector like quarks and leptons are generated by demanding that the corresponding intersections respect N=1 supersymmetry. When we generate the value of ${\tilde ν}_R$ at 750 GeV, by varying the complex structure of the torus, the string scale is limited to be in the range $ 10^{14} < M_s < 10^{19}$ GeV. Also, generating the Higgs scalars by imposing N=1 supersymmetry on intersections fixes naturally, to zero, the coupling of the axion to SU(2) gauge bosons $\propto F_b \wedge F_b$ and in photon-photon fusion also decouples its coupling from $G^2$ of color SU(3) by simultaneously generating the superpartners of $q_L$, $U_R$, $l_L$, $ν_R$ quarks and leptons.

hep-ph↗

arXiv2014

Standard Models and Split Supersymmetry from Intersecting Brane Orbifolds

We construct four dimensional three generation non-supersymmetric $SU(3)_c \times SU(2)_L \times U(1)_Y$ intersecting D6-brane models with $ν_R$\rq{s}. At three stacks we find exactly the MSSM chiral fermion matter spectrum. At 4-, 5-stacks we find models with the massless fermion spectrum of the N=1 Standard Model and massive exotic non-chiral matter; these models flow also to only the SM. At 8-stacks we find MSSM-like models, with minimal massless exotics, made from two different N=1 sectors. Exotic triplet masses put a lower bound on the string scale of $2.79/2.89 \times 10^6$ GeV for a Higgs 124/126 GeV. It\rq{}s the first appearance of N=0 stringy quivers with the MSSM and matter in antisymmetric representations and perturbatively missing Yukawa couplings. The present models are based on orientifolds of ${\bf T^6/(Z_3 \times Z_3)}$ compactifications of IIA theory based on the torus lattice AAA; all complex moduli are fixed by the orbifold symmetry. We also present the spectrum rules + GS anomaly cancellation for the ABB lattice. Moreover, we point out the relevance of intersecting/and present D6-brane constructions on ideas related to existence of split supersymmetry in nature. In this context we present non-susy models with only the SM-matter and also MSSM-matter dominated models, with massive gauginos and light higgsinos, that achieve the correct supersymmetric GUT value for the Weinberg angle $sin^2 θ= \frac{3}{8}$ at a string scale $5 \cdot 10^{13} \ GeV < M_{S} < 1.4 \cdot 10^{17}$ GeV. It appears that if only the SM survives at low energy the unification scale is preserved at $5.03 \times 10^{13}$ GeV when n$_H$ =1, 3, 6. These models support the existence of split supersymmetry scenario in string theory.

hep-th↗

arXiv2009

Quark Masses from Gaugino Condensation in String Theories

We present a mechanism able to generate the perturbatively absent up/down $<{\bf 10} \cdot {\bf 10} \cdot {\bf 5}^H>$ quark Yukawa couplings of SU(5)/flipped SU(5) GUTS in Type II orientifold compactifications with D-branes. The mechanism works when there are Sp(N) gauge groups involved. The ${\bf {\bar 5}}$'s get charged under the Sp(N) gauge groups and the generation of quark masses proceeds via the generation of the fermionic Sp(N) singlet condensate $<{\bf {\bar 5} \cdot {\bar 5} \cdot {\bar 5} \cdot {\bar 5}}>$ in the term $(1/{M_s^5}) {\bf 10} \cdot {\bf 10} \cdot < {\bf {\bar 5} \cdot {\bar 5} \cdot {\bar 5} \cdot {\bar 5}}>$. Also non-chiral states charged under Sp gauge groups may become constrained by the requirement of Sp's becoming strongly coupled.

hep-th↗

arXiv2009

On the (Non) Perturbative Origin of Quark Masses in D-brane GUT Models

We examine the issue of generating the perturbatively absent ${\bf 10} \cdot {\bf 10} \cdot {\bf 5}^H$ SU(5)/flipped SU(5)Yukawa couplings in type II D-brane orientifold compactifications of string theory both at the perturbative (PER) and the non-perturbative (NP) level. We find at the PER level, higher order terms like $ {\bf 10} \cdot {\bf 10} \cdot {\bf{\bar 5}}^H \cdot{\bf{\bar 5}}^H \cdot {\bf{\bar 5}}^H \cdot {\bf{\bar 5}}^H \cdot {\bf 1}^H \cdot {\bf 1}^H$ in SU(5) may be responsible for the relevant quark mass generation in models with general intersecting D6-branes. Euclidean D2-brane instantons on the other hand can also generate at the NP via the term ${\bf 10} \cdot {\bf 10} \cdot {\bf{\bar 5}}^H \cdot{\bf{\bar 5}}^H \cdot {\bf{\bar 5}}^H \cdot {\bf{\bar 5}}^H $ the relevant quark masses by the use of just the $U(1)_b$ brane, for SU(5) and flipped SU(5) GUTS classes of models. We provide local examples of rigid O(1) instantons within the $T^6/{\mathbb Z}_2 \times {\mathbb Z}_2'$ toroidal orientifold with torsion, whose NP contribution to the masses gets minimal as it is induced by just a duplicated disk diagram.

hep-th↗

arXiv2006

MSSM GUT String Vacua, Split Supersymmetry and Fluxes

We show that previous proposals to accommodate the MSSM with string theory N=0 non-supersymmetric compactifications coming from intersecting D6-branes may be made fully consistent with the cancellation of RR tadpoles. In this respect we present the first examples of non-supersymmetric string Pati-Salam model vacua with starting observable gauge group $SU(4)_c \t SU(2)_L \t SU(2)_R$ (SU(2) from Sp(2)'s) that accommodate the spectrum of the 3 generation MSSM with a gauged baryon number with all extra exotics (either chiral or non-chiral) becoming massive and all MSSM Yukawas realized. The N=1 supersymmetry of the visible sector is broken by an extra supersymmetry messenger breaking sector that preserves a different N$^{\prime}$=1 susy, exhibiting the first examples of stringy gauge mediated models. Due to the high scale of the models, these models are also the first realistic examples of carriers of stringy split supersymmetry exhibiting universal slepton/squark masses, massive string scale gauginos, {\em unification of SU(3), SU(2) gauge couplings at} $2.04 \times 10^{16}$ GeV, a stable proton and the appearance of a landscape split SM with chiral fermions and only Higgsinos below the scale of susy breaking; the LSP neutralino candidate could also be only Higgsino or Higgsino-Wino mixture. We also add RR, NS and metric fluxes as every intersecting D-brane model without fluxes can be accommodated in the presence of fluxes. The addition of metric fluxes in the toroidal lattice also stabilizes the expected real parts of all in AdS closed string moduli (modulo D-term affects), leaving unfixed only the imaginary parts of Kähler moduli.

hep-th↗

arXiv2005

Standard Model Compactifications of IIA Z3 x Z3 Orientifolds from Intersecting D6-branes

We discuss the construction of chiral four dimensional ${\bf T^6/(Z_3 \times Z_3)}$ orientifold compactifications of IIA theory, using D6-branes intersecting at angles and not aligned with the orientifold O6 planes. Cancellation of mixed U(1) anomalies requires the presence of a generalized Green-Schwarz mechanism mediated by RR partners of closed string untwisted moduli. In this respect we describe the appearance of three quark and lepton family $SU(3)_C \times SU(2)_L \times U(1)_Y$ non-supersymmetric orientifold models with only the massless spectrum of the SM at low energy that can have either no exotics present and three families of $ν_R$'s (A$^{\prime}$-model class) or the massless fermion spectrum of the N=1 SM with a small number of massive non-chiral colour exotics and in one case with extra families of $ν_R$'s (B$^{\prime}$-model class). Moreover we discuss the construction of SU(5), flipped SU(5) and Pati-Salam $SU(4)_c \times SU(2)_L \times SU(2)_R$ GUTS - the latter also derived from adjoint breaking - with only the SM at low energy. Some phenomenological features of these models are also briefly discussed. All models are constructed with the Weinberg angle to be 3/8 at the string scale.

hep-th↗

arXiv2004

Standard Model Building from Intersecting D-Branes

We provide a general overview of the current state of the art in four dimensional three generation model building proposals - using intersecting D-brane toroidal compactifications [without fluxes] of IIA, IIB string theories - which have only the SM at low energy. In this context, we focus on these model building directions, where non-supersymmetric constructions - based on the existence of the gauge group structure $SU(3)_c \times SU(2)_L \times U(1)_Y$, Pati-Salam $SU(4)_C \times SU(2)_L \times SU(2)_R$, SU(5) and flipped SU(5) GUTS - appear at the string scale $M_s$. These model building attempts are based on four dimensional compactifications that use orientifolds of either IIA theory with D6-branes wrapping on $T^6$, $T^6/Z_3$ and recently on $T^6/Z_3 \times Z_3$ or of IIB theory with D5-branes wrapping on $T^4 \times C/Z_N$. Models with D5-branes are compatible with the large extra dimension scenario and a low string scale that could be at the TeV; thus there is no gauge hierarchy problem in the Higgs sector. In the case of flipped SU(5) GUTS - coming from $T^6/Z_3$ - the special build up structure of the models accommodates naturally a see-saw mechanism and a new solution to the doublet-triplet splitting problem. Baryon number is a gauged symmetry and thus proton is naturally stable only in models with D5 branes or in models with D6-branes wrapping toroidal orientifolds of type IIA. Finally, we present new RR tadpole solutions for the 5- and 6- stack toroidal orientifold models of type IIA which have only the Standard Model with right handed neutrinos at low energy.

hep-th↗

arXiv2004

Beyond the SM; D-brane model building from intersecting brane worlds

We discuss the appearance of non-supersymmetric D6-brane GUT model constructions. We focus on the construction of the first examples of flipped SU(5) and SU(5) GUTS which have only the SM at low energy. These constructions are based on 4D compactifications in Z3 toroidal orientifolds of type IIA with D6-branes intersecting at angles.

hep-th↗

arXiv2003

4D GUT (and SM) Model Building from Intersecting D-Branes

We provide a general overview of the current state of the art in three generation model building proposals - using intersecting D-brane toroidal compactifications of IIA string theories - which have, only, the SM at low energy. In this context, we focus on these model building directions, where natural non-supersymmetric constructions based on $SU(4)_C \times SU(2)_L \times SU(2)_R$, SU(5) and flipped SU(5) GUT groups, have at low energy only the Standard Model. In the flipped SU(5) GUTS, the special build up structure of the models accommodates naturally a see-saw mechanism and a new solution to the doublet-triplet splitting problem.

hep-th↗

arXiv2003

N=1 Locally Supersymmetric Standard Models from Intersecting Branes

We construct four dimensional intersecting D6-brane models that have locally the spectrum of the N=1 Supersymmetric Standard Model. All open {\em visible} string sectors share the same N=1 supersymmetry. As expected in these supersymmetric classes of models, where the D6-branes wrap a toroidal orientifold of type IIA, the hierarchy may be stabilized if the string scale is low, e.g. below 30 TeV. We analyze the breaking of supersymmetry in the vicinity of the supersymmetric point by turning on complex structure deformations as Fayet-Iliopoulos terms. Positive masses for all squarks and sleptons, to avoid charge/colour breaking minima, may be reached when also two loop contributions may be included. In the ultimate version of the present models N=1 supersymmetry may be broken by gauge mediation. The constructions with four, five and six stacks of D6-branes at $M_s$ are build directly. Next by the use of brane recombination we are able to show that there is a continuous, RR homology flow, between six, five and four stack models. Moreover, we examine the gauge coupling constants of the Standard Model $SU(3)_C$, $SU(2)_L$, $U(1)_Y$ at the string scale in the presence of a non-zero antisymmetric NS B-field.

hep-th↗

arXiv2003

SU(5) Unified Theories from Intersecting Branes

We discuss the first string theory examples of three generation non-supersymmetric SU(5) and {\em flipped} SU(5) GUTS, which break to the Standard model at low energy, without extra matter and/or gauge group factors. Our GUT examples are based on IIA $Z_3$ orientifolds with D6-branes intersecting at non-trivial angles. These theories necessarily satisfy RR tadpoles and are free of NSNS tadpoles as the complex structure moduli are frozen (even though a dilaton tadpole remains) to discrete values. We identify appropriately the bifundamental Higgses responsible for electroweak symmetry breaking. In this way, the neutrino see-saw mechanism get nicely realized in these constructions. Moreover, as baryon number is not a gauged symmetry gauge mediated dimension six operators do contribute to proton decay; however proton lifetime may be safely enhanced by appropriately choosing a high GUT scale. An accompanying natural doublet-triplet splitting guarantees the suppression of scalar mediated proton decay modes and the stability of triplet scalar masses against higher dimensional non-renormalizable operators.

hep-th↗

arXiv2003

Exact Standard model Structures from Intersecting D5-Branes

We discuss the appearance of non-supersymmetric compactifications with exactly the Standard Model (SM) at low energies, in the context of IIB orientifold constructions with D5 branes intersecting at angles on the $T^4$ tori, of the orientifold of $T^4 \times (\C /Z_N)$. We discuss constructions where the Standard Model embedding is considering within four, five and six stacks of D5 branes. The appearance of the three generation observable Standard Model at low energies is accompanied by a gauged baryon number, thus ensuring automatic proton stability. Also, a compatibility with a low scale of order TeV is ensured by having a two dimensional space transverse to all branes. The present models complete the discussion of some recently constructed four stack models of D5 branes with the SM at low energy. By embedding the four, five and six stack Standard Model configurations into quiver diagrams, deforming them around the QCD intersection numbers, we find a rich variety of vacua that may have exactly the Standard Model at low energy. Also by using brane recombination on the U(1)'s, we show that the five and six vacua flow into their four stack counterparts. Thus string vacua with five and six stack deformations are continuously connected to the four stack vacua.

hep-th↗

arXiv2003

Deformed Intersecting D6-Brane GUTS and N=1 SUSY

We analyze the construction of non-supersymmetric three generation six-stack Pati-Salam (PS) $SU(4)_C \times SU(2)_L \times SU(2)_R$ GUT classes of models, by localizing D6-branes intersecting at angles in four dimensional orientifolded toroidal compactifications of type IIA. Special role in the models is played by the presence of extra branes needed to satisfy the RR tadpole cancellation conditions. The models contain at low energy {\em exactly the Standard model} with no extra matter and/or extra gauge group factors. They are build such that they represent deformations around the quark and lepton basic intersection number structure. The models possess the same phenomenological characteristics of some recently discussed examples (PS-A, PS-I; PS-II GUT classes; hep-th/0203187, hep-th/0209202; hep-th/0210004) of four and five stack PS GUTS respectively. Namely, there are no colour triplet couplings to mediate proton decay and proton is stable as baryon number is a gauged symmetry. The mass relation $m_e = m_d$ at the GUT scale is recovered. Even though more complicated, than in lower stack GUTS, the conditions of the non-anomalous U(1)'s to survive massless the generalized Green-Schwarz mechanism are solved consistently by the angle conditions coming from the presence of N=1 supersymmetric sectors involving the presence of {\em extra} branes and also required for the existence of a Majorana mass term for the right handed neutrinos.

hep-th↗

arXiv2002

Deformed Intersecting D6-Brane GUTS I

By employing D6-branes intersecting at angles in $D = 4$ type IIA strings, we construct {\em four stack string GUT models} (PS-I class), that contain at low energy {\em exactly the three generation Standard model} with no extra matter and/or extra gauge group factors. These classes of models are based on the Pati-Salam (PS) gauge group $SU(4)_C \times SU(2)_L \times SU(2)_R$. They represent deformations around the quark and lepton basic intersection number structure. The models possess the same phenomenological characteristics of some recently discussed examples (PS-A class) of four stack PS GUTS. Namely, there are no colour triplet couplings to mediate proton decay and proton is stable as baryon number is a gauged symmetry. Neutrinos get masses of the correct sizes. Also the mass relation $m_e = m_d$ at the GUT scale is recovered. Moreover, we clarify the novel role of {\em extra} branes, the latter having non-trivial intersection numbers with quarks and leptons and creating scalar singlets, needed for the satisfaction of RR tadpole cancellation conditions. The presence of N=1 supersymmetry in sectors involving the {\em extra} branes is equivalent to the, model dependent, orthogonality conditions of the U(1)'s surviving massless the generalized Green-Schwarz mechanism. The use of {\em extra} branes creates mass couplings that predict the appearance of light fermion doublets up to the scale of electroweak scale symmetry breaking.

hep-th↗

arXiv2002

Standard Model Compactifications from Intersecting Branes

We discuss the construction of four dimensional non-supersymmetric models obtained from configurations of D6-branes intersecting at angles. We present the first examples of string GUT models which break exactly to the Standard Model (SM) at low energy. Even though the models are non supersymmetric (SUSY), the demand that some open string sectors preserve N=1 SUSY creates gauge singlet scalars that break the extra anomaly free U(1)'s generically present in the models, predicting $s{\tilde ν}_R$'s and necessarily creating Majorana mass terms for right handed neutrinos.

hep-th↗

arXiv2002

Deformed Intersecting D6-Brane GUTS II

By employing D6-branes intersecting at angles in $D = 4$ type I strings, we construct {\em five stack} string GUT models (PS-II class), that contain at low energy {\em exactly the Standard model} with no extra matter and/or extra gauge group factors. These classes of models are based on the Pati-Salam (PS) gauge group $SU(4)_C \times SU(2)_L \times SU(2)_R$. They represent deformations around the quark and lepton basic intersection number structure. The models possess the same phenomenological characteristics of some recently discussed examples (PS-A and PS-I class) of four stack PS GUTS. Namely, there are no colour triplet couplings to mediate proton decay and proton is stable as baryon number is a gauged symmetry. Neutrinos get masses of the correct sizes. Also the mass relation $m_e = m_d$ at the GUT scale is recovered. The conditions for the non-anomalous U(1)'s to survive massless the Green-Schwarz mechanism are equivalent, to the conditions, coming from the presence of N=1 supersymmetry, in sectors involving the presence of {\em extra} branes and also required to guarantee the existence of the Majorana mass term for the right handed neutrinos. These conditions are independent from the number of {\em extra} U(1) branes. We also discuss the relative size of the leading worldsheet instanton correction to the trilinear Yukawa couplings in a general GUT model.

hep-th↗