15 citations · 160 across the 29 of their papers we have counts for
30 papers
Araki Cohomology of the de Sitter Scalar Discrete Series
Maryam Bajalan, Jean-Pierre Gazeau, Hamed Pejhan +1
Building on the recently established de Sitter (dS)-covariant indecomposable Krein realization of the scalar discrete-series unitary irreducible representations , $p=1,2,\…
de Sitter Scalar Discrete Series: Gupta-Bleuler Structure and Holography
Maryam Bajalan, Jean-Pierre Gazeau, Hamed Pejhan
We show that scalar discrete-series unitary irreducible representations (UIRs) () of the de Sitter (dS) group admit a dS-covariant Krei…
Infrared Spectral Gap in a Gluonic Dark Sector and the Galactic Acceleration Scale
Gilles Cohen-Tannoudji, Jean-Pierre Gazeau, Hamed Pejhan +1
We further develop a trace-anomaly-motivated gluonic scenario in which cold dark matter (CDM) is modeled as a long-lived color-singlet Bose-Einstein condensate seeded at the QCD co…
Massless Representations in Conformal Space and Their de Sitter Restrictions
Jean-Pierre Gazeau, Hamed Pejhan, Ivan Todorov
The monograph offers a coherent and self-contained treatment of massless (ladder) representations of the conformal group U(2,2) and their restriction to the de Sitter group Sp(2,2)…
Holomorphic Discrete Series of SU(1,1): Orthogonality Relations, Character Formulas, and Multiplicities in Tensor Product Decompositions
Jean-Pierre Gazeau, Mariano A. del Olmo, Hamed Pejhan
The SU group plays a fundamental role in various areas of physics, including quantum mechanics, quantum optics, and representation theory. In this work we revisit the holomo…
A unified framework for graviton, "partially massless" graviton, and photon fields in de Sitter spacetime under conformal symmetry
Jean-Pierre Gazeau, Hamed Pejhan
We develop a conformally invariant (CI) framework in -dimensional de Sitter (dS) spacetime, that unifies the descriptions of graviton, ``partially massless'' graviton, and p…
Matter-antimatter (a)symmetry in de Sitter Universe
Jean-Pierre Gazeau, Hamed Pejhan
We investigate the matter-antimatter properties of elementary systems, modeled as free quantum fields, within the global structure of de Sitter spacetime. By leveraging the distinc…
Matrix Elements and Characters of the Discrete Series ("Massive") Unitary Irreducible Representations of Sp(4,R)
Jean-Pierre Gazeau, Mariano A. del Olmo, Hamed Pejhan
This paper obtains the matrix elements and characters of the discrete series unitary irreducible representations (UIRs) of the Sp group. With an isomorphic relation…
A misleading naming convention: de Sitter `tachyonic' scalar fields
Jean-Pierre Gazeau, Hamed Pejhan
We revisit the concept of de Sitter (dS) 'tachyonic' scalar fields, characterized by discrete negative squared mass values, and assess their physical significance through a rigorou…
de Sitter Relativity Group
Hamed Pejhan
Building upon the comprehensive framework outlined in the author's recent collaborative book, this manuscript delivers a brief overview of the -dimensional de Sitter (dS)…
A Novel Holographic Framework Preserving Reflection Positivity in dS Spacetime
Jean-Pierre Gazeau, Mariano A. del Olmo, Hamed Pejhan
This manuscript introduces a novel holographic correspondence in -dimensional de Sitter (dS) spacetime, connecting bulk dS scalar unitary irreducible representations (UI…
Anti-de Sitterian "massive" elementary systems and their Minkowskian and Newton-Hooke contraction limits
Mohammad Enayati, Jean-Pierre Gazeau, Mariano A. del Olmo +1
We elaborate the definition and properties of "massive" elementary systems in the -dimensional Anti-de Sitter (AdS) spacetime, on both classical and quantum levels. We f…
Covariant Quantization of the Partially Massless Graviton Field in de Sitter Spacetime
Jean-Pierre Gazeau, Hamed Pejhan
We present a covariant quantization scheme for the so-called "partially massless" graviton field in de Sitter spacetime. Our approach is founded on the principles of the de Sitter…
The de Sitter group and its representations: a window on the notion of de Sitterian elementary systems
Mohammad Enayati, Jean-Pierre Gazeau, Hamed Pejhan +1
We review the construction of ("free") elementary systems in de Sitter (dS) spacetime, in the Wigner sense, as associated with unitary irreducible representations (UIR's) of the dS…
"Massive" Rarita-Schwinger field in de Sitter space
Hamed Pejhan, Mohammad Enayati, Jean-Pierre Gazeau +1
We present a covariant quantization of the "massive" spin- Rarita-Schwinger field in de Sitter (dS) spacetime. The dS group representation theory and its Wigner inte…
Gupta-Bleuler quantization for linearized gravity in de Sitter spacetime
Hamed Pejhan, Mohammad Enayati, Jean-Pierre Gazeau +1
In a recent Letter, we have pointed out that the linearized Einstein gravity in de Sitter (dS) spacetime besides the spacetime symmetries generated by the Killing vectors and the e…
`Hidden' symmetry of linearized gravity in de Sitter space
Hamed Pejhan, Surena Rahbardehghan, Mohammad Enayati +2
We demonstrate that the linearized Einstein gravity in de Sitter (dS) spacetime besides the evident symmetries also possesses the additional (local) symmetry $h_{μν}\rightarrow h_{…
A small non-vanishing cosmological constant from the Krein-Gupta-Bleuler vacuum
Hamed Pejhan, Kazuharu Bamba, Mohammad Enayati +1
We point out a potential relevance between the Krein-Gupta-Bleuler (KGB) vacuum leading to a fully covariant quantum field theory for gravity in de Sitter (dS) spacetime and the ob…
"Massless" spin-2 field in de Sitter space
Hamed Pejhan, Kazuharu Bamba, Surena Rahbardehghan +1
In this paper, admitting a de Sitter (dS)-invariant vacuum in an indefinite inner product space, we present a Gupta-Bleuler type setting for causal and full dS-covariant quantizati…
Vacuum states for gravitons field in de Sitter space
Kazuharu Bamba, Surena Rahbardehghan, Hamed Pejhan
In this paper, considering the linearized Einstein equation with a two-parameter family of linear covariant gauges in de Sitter spacetime, we examine possible vacuum states for the…
On the graviton two-point function and its infrared behavior in de Sitter spacetime
Surena Rahbardehghan, Hamed Pejhan
In our previous paper (Phys. Rev. D 94, 104030 (2016)), inspired by the work of Allen and Turyn (Nucl. Phys. B 292, 813 (1987)), we expressed the graviton two-point function in ter…
Covariant and infrared-free graviton two-point function in de Sitter spacetime II
Hamed Pejhan, Surena Rahbardehghan
The solution to the linearized Einstein equation in de Sitter (dS) spacetime and the corresponding two-point function are explicitly written down in a gauge with two parameters `$a…
Casimir energy-momentum tensor for a quantized bulk scalar field in the geometry of two curved branes on Friedmann-Robertson-Walker background
Hamed Pejhan, Surena Rahbardehghan
In a previous work [S. Rahbardehghan et al. in Phys. Lett. B 750, 627 (2015)], we considered a simple brane-world model; a single -dimensional brane embedded in a -dimensiona…
Covariant and infrared-free graviton two-point function in de Sitter spacetime
Hamed Pejhan, Surena Rahbardehghan
In this paper, the two-point function of linearized gravitons on de Sitter (dS) space is presented. Technically, respecting the dS ambient space notation, the field equation is giv…