111 research outputs found
Phases of quartic scalar theories and PT symmetry
Full text linkFor quantum mechanical anharmonic oscillator-type Hamiltonians, it is shown that there is a relation between the energy eigenvalues of parity symmetric and PT-symmetric phases for weak coupling. The possibility of such a relation was conjectured by Ai, Bender, and Sarkar on examining the imaginary part of the ground state energy using path integrals. In the weak coupling limit, we show that the conjecture is true also for the real part of the ground state energy and of the excited state energies. However, the conjecture is false for strong coupling. The analogous relation for partition functions in zero spacetime dimensions is valid for many cases. However O(N) symmetric multicomponent scalar fields, with N>1 and a quartic interaction, do not satisfy the conjecture for zero and one dimensional spacetime. The possibility that the conjecture is valid, for a single component field theory in higher dimensional spacetimes, is discussed in a simplified model.</p
Magnetic Global Monopoles from Torsion
No full textIn the search of avatars of new physics, we present a new classical solution for electromagnetic monopoles induced by global gravitational monopoles in the presence of a four-dimensional Kalb-Ramond axion field. The torsion induces the magnetic charge of the monopole
Anomalies, CPT and Leptogenesis
Full text linkWe bring together different puzzles in physics beyond the Standard Model of
particle physics. Within our model baryogenesis, neutrino mass, strong CP and
dark matter puzzles are related. The common ingredient in connecting these
puzzles is the Kalb-Ramond field, a two form present in the gravitational
multiplet in the theory of closed strings. Leptons are fermions which we need
to couple to gravitational degrees of freedom using a vierbein formalism. The
presence of torsion provided by a Kalb-Ramond background leads us to firstly an
effective model involving the Einstein-Cartan formulation of gravity, a gauge
theory, in which coupling to fermions is via a covariant derivative and
secondly to a mechanism for CPT violation. This picture emerges from a low
energy string effective action obtained from a closed bosonic string theory
after compactification to four dimensions. The Kalb-Ramond field in four
dimensions can be identified with a pseudoscalar gravitational axion. Because
of the presence of an axial anomaly this axion can couple with the gluon field,
and in this way allows a connection with the strong CP problem and axionic dark
matter
String Theory backgrounds with Torsion in the presence of Fermions and implications for Leptogenesis
Full text linkFermions couple in a universal way to the the Kalb-Ramond field which occurs in the gravitational multiplet of string theory. The Kalb-Ramond field is a source of torsion and can provide a background for fermion dynamics. Solutions for this background in terms of the string effective action are discussed and are fixed "points" of conformal invariance conditions. Non- perturbative fixed points for the torsion in the absence of matter are shown to be compatible with perturbative fixed points in the presence of matter. Fermion coupling to such backgrounds can lead to both CP and CPT violation. Hence torsion can give a new mechanism for leptogenesis. The presence of anomalies in the Bianchi identity for the torsion, in the presence of matter, is crucial in giving a background solution for the torsion and dilaton with an acceptable cosmology.</p
D-foam-induced flavor condensates and breaking of supersymmetry in free Wess-Zumino fluids
No full textRecently {[}N. E. Mavromatos and S. Sarkar, New J. Phys. 10, 073009 (2008); N. E. Mavromatos, S. Sarkar, and W. Tarantino, Phys. Rev. D 80, 084046 (2009)], we argued that a particular model of string-inspired quantum space-time foam (D-foam) may induce oscillations and mixing among flavored particles. As a result, rather than the mass-eigenstate vacuum, the correct ground state to describe the underlying dynamics is the flavor vacuum, proposed some time ago by Blasone and Vitiello as a description of quantum field theories with mixing. At the microscopic level, the breaking of target-space supersymmetry is induced in our space-time foam model by the relative transverse motion of brane defects. Motivated by these results, we show that the flavor vacuum, introduced through an inequivalent representation of the canonical (anti-) commutation relations, provides a vehicle for the breaking of supersymmetry at a low-energy effective field-theory level; on considering the flavor-vacuum expectation value of the energy-momentum tensor and comparing with the form of a perfect relativistic fluid, it is found that the bosonic sector contributes as dark energy while the fermion contribution is like dust. This indicates a strong and novel breaking of supersymmetry, of a nonperturbative nature, which may characterize the low-energy field theory of certain quantum-gravity models.Recently we argued that a particular model of string-inspired quantum space-time foam (D-foam) may induce oscillations and mixing among flavoured particles. As a result, rather than the mass-eigenstate vacuum, the correct ground state to describe the underlying dynamics is the flavour vacuum, proposed some time ago by Blasone and Vitiello as a description of quantum field theories with mixing. At the microscopic level, the breaking of target-space supersymmetry is induced in our space-time foam model by the relative transverse motion of brane defects. Motivated by these results, we show that the flavour vacuum, introduced through an inequivalent representation of the canonical (anti-) commutation relations, provides a vehicle for the breaking of supersymmetry (SUSY) at a low-energy effective field theory level/ on considering the flavour-vacuum expectation value of the energy-momentum tensor and comparing with the form of a perfect relativistic fluid, it is found that the bosonic sector contributes as dark energy while the fermion contribution is like dust. This indicates a strong and novel breaking of SUSY, of a non-perturbative nature, which may characterize the low energy field theory of certain quantum gravity models
D-foam-induced flavor condensates and breaking of supersymmetry in free Wess-Zumino fluids
No full textRecently [N. E. Mavromatos and S. Sarkar, New J. Phys. 10, 073009 (2008); N. E. Mavromatos, S. Sarkar, and W. Tarantino, Phys. Rev. D 80, 084046 (2009)], we argued that a particular model of string-inspired quantum space-time foam (D-foam) may induce oscillations and mixing among flavored particles. As a result, rather than the mass-eigenstate vacuum, the correct ground state to describe the underlying dynamics is the flavor vacuum, proposed some time ago by Blasone and Vitiello as a description of quantum field theories with mixing. At the microscopic level, the breaking of target-space supersymmetry is induced in our space-time foam model by the relative transverse motion of brane defects. Motivated by these results, we show that the flavor vacuum, introduced through an inequivalent representation of the canonical (anti-) commutation relations, provides a vehicle for the breaking of supersymmetry at a low-energy effective field-theory level; on considering the flavor-vacuum expectation value of the energy-momentum tensor and comparing with the form of a perfect relativistic fluid, it is found that the bosonic sector contributes as dark energy while the fermion contribution is like dust. This indicates a strong and novel breaking of supersymmetry, of a nonperturbative nature, which may characterize the low-energy field theory of certain quantum-gravity models
On the possibility of tree-level leptogenesis from Kalb–Ramond torsion background
Full text linkThe effect of torsion in theories of quantum gravity is known to be well described by an axion-like field which couples to matter as well as to gravitation and radiation gauge fields. In this note we consider a particular kind of torsion, arising from the Kalb-Ramond antisymmetric tensor field that appears in the gravitational multiplet of string theory. We investigate the implications for leptogenesis. It is shown that leptogenesis can occur even at tree-level and with only one generation of right-handed Majorana neutrinos, due to CP and CPT violation introduced by the background geometry.In this work we consider a phenomenological model for leptogenesis in the context of a Standard Model Extension with an axial-like background coupling to fermions that violates both Lorentz and CPT symmetries. The latter is motivated by a background geometry of the early Universe involving a particular kind of torsion, arising from the Kalb–Ramond antisymmetric tensor field which appears in the gravitational multiplet of string theory, although we do not restrict ourselves to this framework. It is shown that leptogenesis can occur even at tree level and with only one generation of right-handed heavy Majorana neutrinos, due to and CPT violation introduced by the background geometry. Important issues for the model, including (a) its compatibility with a conventional-like cosmology and (b) current-era phenomenology (characterised by very stringent bounds on the allowed amount of torsion) are pointed out, and potential ways of resolving them, within the framework of string-theory models, are discussed.The effect of torsion in theories of quantum gravity is known to be well described by an axion-like field which couples to matter as well as to gravitation and radiation gauge fields. In this note we consider a particular kind of torsion, arising from the Kalb-Ramond antisymmetric tensor field that appears in the gravitational multiplet of string theory. We investigate the implications for leptogenesis. It is shown that leptogenesis can occur even at tree-level and with only one generation of right-handed Majorana neutrinos, due to CP and CPT violation introduced by the background geometry
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