arXiv subjects

Massimo Porrati

Publications and source records attributed to Massimo Porrati.

At least 19 recordsLinked to original sources

arXiv2026

Holomorphic structure of massive scalar fields in $\text{(A)dS}_2$

Scalar field theories in $\text{(A)dS}_{2}$ with integer scaling dimensions $\Delta = k+1$ are characterised by the existence of a pair of (anti-)holomorphic higher-spin currents. We explore the consequences of this to describe their quantisation and subsets of their linear and non-linear symmetries, taking care to treat $\text{AdS}_{2}$ and $\text{dS}_{2}$ separately. In particular, we point out that the theories admit mode expansions reminiscent of standard two-dimensional conformal field theories in complex coordinates, with which we are able to construct operators implementing global conformal and Virasoro symmetry. We further leverage holomorphicity of the currents to show that the full set of symmetries of theories with $k>0$ is captured by a chiral algebra, which is a subalgebra of the one in the $k=0$ (massless) theory. This allows us to identify integrable deformations for $k \in \{0,1,2\}$. We finally observe that a lack of integrable deformations for $k>2$ is a consequence of a known conjecture.

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arXiv2026

$T\bar T$ Deformations through BRST Symmetry

We study the $T\bar T$ deformation using its formulation as a CFT coupled to two-dimensional dynamical gravity. Working within the BRST formalism, we apply the intertwiner construction of arXiv:2411.08865 to obtain a unitary "dressing" map between undeformed CFT operators and elements of the BRST cohomology of the deformed theory. We identify the resulting "dressed" operators corresponding to CFT primaries as the physical observables of the deformed theory and show that they arise from a field-dependent change of coordinates, in agreement with what is expected for the $T\bar T$ deformation. We then give a non-perturbative definition of deformed correlation functions as BRST-invariant expectation values of dressed operators in the gauge theory. Finally, we verify that our construction reproduces known structural and perturbative results.

hep-th↗

arXiv2025

Klein Bottle Cosmology

We explore a higher-dimensional universe that is a product of Minkowski space and the nonorientable Klein bottle. The topology explicitly breaks important symmetries, such as translational invariance and (5+1)-dimensional CP invariance. Somewhat surprisingly, the (3+1)-dimensional cp of the Minkowski space can also be broken by the Klein bottle, both explicitly and in the presence of a brane. The topology enforces a background of fermion correlations that amounts to a condensate wall localized in the Klein bottle. The wall acts as an order parameter for the broken symmetries. If a brane passes through the wall, brane fermions that couple to the condensate are produced as quantified by the Bogoliubov coefficients for a time-dependent mass. The scenario meets the conditions, including cp violation, to potentially generate the matter-antimatter asymmetry of the universe.

hep-th↗

arXiv2025

Lorentz Covariant Supertranslation Frames for the Angular Momentum Aspect

In this letter, we review the well known ambiguity in defining angular momentum (and mass dipole) fluxes in general relativity and we reinterpret recent works that resolve the ambiguity by defining invariant charges. We resolve the ambiguity by finding the conditions that fix a frame for supertranslation and for space-time translation. We also present an elementary method for measuring the angular momentum aspect and work out explicitly the supertranslation frame-fixing conditions for the metric created by point particles to first nontrivial order in the Newton constant.

gr-qc↗

arXiv2025

Compactification Without Orientation, or a Topological Scenario for $CP$ Violation

In higher dimensional theories, we often assume that the extra dimensions form an orientable space, perhaps with singularities. However, many physical theories are well-defined on non-orientable spaces, and many spaces are not orientable, so it is reasonable to explore what happens if the assumption of orientability is relaxed. Here we consider the simplest example of free 6D theories compactified on a flat Klein bottle. We focus on a Dirac fermion in 6D, with boundary conditions that define ${\rm pin}^+$ and ${\rm pin}^-$ structures. Translation invariance is broken by the boundary conditions, which leads to sharp features localized near the parity walls (fixed points of the reflection used to construct the Klein bottle). For a scalar field, there is a position-dependent energy density, peaked near the parity walls. A Dirac fermion can lead to breaking of parity, charge conjugation and $CP$ in 3+1 dimensions. Order parameters for this breaking are provided by the vevs of certain fermion bilinears, again peaked near the parity walls. As one potential application, these results suggest mechanisms for $CP$ violation and baryogenesis, enabled by compactification on a Klein bottle.

hep-th↗

arXiv2025

The Chiral Limit of Fully Nonlinear Minimal Massive Gravity

We study 3D Anti de Sitter Minimal Massive Gravity in two regimes: a) at the chiral limit where one of the boundary Brown-Henneaux central charges vanishes and two modes become null and b) in the regime that one of the two charges is much larger than the other. At the chiral point, we go beyond the known free-theory analysis to prove that these modes decouple completely also in the full MMG Lagrangian and field equations. We also use the full action to ascertain if the interacting theory becomes infinitely strongly coupled in the neighborhood of the chiral limit, where the theory is anyway not unitary. We show that this is not the case at tree level but that a strong coupling pathology appears in loops, starting at a loop level determined by the number of external legs in the bulk Feynman diagrams. Finally, we show that there is no strong coupling problem in the second regime where, instead, the two boundary fields and the field propagating in the bulk decouple from one another.

hep-th↗

arXiv2024

Local Operator Algebras of Charged States in Gauge Theory and Gravity

Powerful techniques have been developed in quantum field theory that employ algebras of local operators, yet local operators cannot create physical charged states in gauge theory or physical nonzero-energy states in perturbative quantum gravity. A common method to obtain physical operators out of local ones is to dress the latter using appropriate Wilson lines. This procedure destroys locality, it must be done case by case for each charged operator in the algebra, and it rapidly becomes cumbersome, particularly in perturbative quantum gravity. In this paper we present an alternative approach to the definition of physical charged operators: we define an automorphism that maps an algebra of local charged operators into a (non-local) algebra of physical charged operators. The automorphism is described by a formally unitary intertwiner mapping the exact BRS operator associated to the gauge symmetry into its quadratic part. The existence of an automorphism between local operators and the physical ones, describing charged states, allows to retain many of the results derived in local operator algebras and extend them to the physical-but-nonlocal algebra of charged operators as we discuss in some simple applications of our construction. We also discuss a formal construction of physical states and possible obstructions to it.

hep-th↗

arXiv2024

Supermassive gauginos in supergravity inflation with high-scale SUSY breaking

A model of supergravity inflation we recently proposed can produce slow roll inflation and a realistic spectrum of particles even without F-term supersymmetry breaking. Supersymmetry is broken only by a D-term induced by a recently discovered new type of Fayet-Iliopoulos (FI) term. Almost all supersymmetric partners of the standard model fields can get masses as high as the inflationary Hubble scale. The exception is gauginos, for which the vanishing of F-terms implies an exact cancellation that keeps their masses exactly zero. To cure this problem without spoiling the simplicity of our model we introduce a new term that further enlarges the space of supergravity effective actions. It is an F-term that, similarly to the new FI term, becomes singular in the supersymmetric limit. We show that this term can produce large gaugino masses without altering the spectrum of other states and without lowering the cutoff of the effecive theory.

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arXiv2023

Three Puzzles with Covariance and Supertranslation Invariance of Angular Momentum Flux (with Solutions)

We describe and solve three puzzles arising in covariant and supertranslation-invariant formulas for the flux of angular momentum and other Lorentz charges in asymptotically flat spacetimes: 1) Supertranslation-invariance and covariance imply invariance under spacetime translations; 2) the flux depends on redundant auxiliary degrees of freedom that cannot be set to zero in all Lorentz frames without breaking Lorentz covariance; 3) supertranslation-invariant Lorentz charges do not generate the transformations of the Bondi mass aspect implied by the isometries of the asymptotic metric. In this letter, we solve the first two puzzles by presenting covariant formulas that unambiguously determine the auxiliary degrees of freedom and clarify the last puzzle by explaining the different role played by covariant and canonical charges. Our construction makes explicit the choice of reference frame underpinning seemingly unambiguous results presented in the current literature.

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arXiv2023

Holography for the Trace Anomaly Action

A recently proposed effective action for the trace anomaly describes a tensor-scalar theory that is weakly coupled up to a certain high energy scale, where it becomes strongly interacting. Its ultraviolet completion is obtained by coupling to gravity a quantum field theory in which conformal invariance is spontaneously broken. In this paper, we show that if the field theory that gives rise to the trace anomaly is a large $N_c$ conformal field theory, then the trace anomaly action has a completion above the strong scale in a holographic Randall-Sundrum two-brane theory, with the radion as a low energy remnant of the spontaneously broken conformal symmetry. Furthermore, we note that the sub-leading $N_c$ terms can be derived by adding localized fields to the UV brane, so that the theory remains weakly coupled. The sub-leading terms are also obtained by introducing the Weyl squared terms in the 5D bulk. These, however, exhibit strongly coupled behavior at the respective sub-Planckian energy scales.

hep-th↗

arXiv2023

Topological Gauging and Double Current Deformations

We study solvable deformations of two-dimensional quantum field theories driven by a bilinear operator constructed from a pair of conserved $U(1)$ currents $J^a$. We propose a quantum formulation of these deformations, based on the gauging of the corresponding symmetries in a path integral. This formalism leads to an exact dressing of the $S$-matrix of the system, similarly as what happens in the case of a $\mathrm{T}\overline{\mathrm{T}}$ deformation. For conformal theories the deformations under study are expected to be exactly marginal. Still, a peculiar situation might arise when the conserved currents $J^a$ are not well-defined local operators in the original theory. A simple example of this kind of system is provided by rotation currents in a theory of multiple free, massless, non-compact bosons. We verify that, somewhat unexpectedly, such a theory is indeed still conformal after deformation and that it coincides with a TsT transformation of the original system. We then extend our formalism to the case in which the conserved currents are non-Abelian and point out its connection with Deformed T-dual Models and homogeneous Yang-Baxter deformations. In this case as well the deformation is based on a gauging of the symmetries involved and it turns out to be non-trivial only if the symmetry group admits a non-trivial central extension. Finally we apply what we learned by relating the $\mathrm{T}\overline{\mathrm{T}}$ deformation to the central extension of the two-dimensional Poincar\'{e} algebra.

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arXiv2023

Back to the Future: Causality on a Moving Braneworld

Brane observers executing appropriate motion through a partially compactified Lorentz invariant bulk spacetime, such as $M_4 \times S^1$, can send signals along the brane that are instantaneous or even travel backward in time. Nevertheless, causality in the braneworld remains intact. We establish these results, which follow from superluminal signal propagation reported in arXiv:2206.13590, through classical analysis and then extend our reasoning by examining quantum mechanical microcausality. One implication is the capacity for real time communication across arbitrarily large distances.

gr-qc↗

arXiv2022

A Supertranslation-Invariant Formula for the Angular Momentum Flux in Gravitational Scattering

The angular momentum radiated in gravitational scattering can be changed by performing a supertranslation of the asymptotic metric, i.e. by adding radiation with infinite wavelenght to the metric. This puzzling property can be avoided by adopting a supertranslation-invariant definition of the angular momentum flux in general relativity. Definitions currently available in the literature cannot reproduce the flux necessary to obtain the correct radiation reaction effects in gravitational scattering. They also disagree with computations of the flux performed using scattering amplitudes and soft graviton theorems. In this paper we provide a new supertranslation-invariant definition of the angular momentum flux in gravitational scattering that uses only asymptotic metric data and reproduces the flux necessary to obtain the correct radiation reaction effects.

gr-qc↗

arXiv2022

A Realization of Slow Roll Inflation and the MSSM in Supergravity Theories with New Fayet-Iliopoulos Terms

A new supergravity D-term, not associated to gauged R-symmetry, was recently discovered and used to construct new supergravity models. In this paper we use a generalization of the new D-term that we used in previous works, to construct a supergravity model of slow-roll inflation with the observable sector of the minimal supersymmetric standard model. Supersymmetry is broken at a high scale in the hidden sector and communicated to the observable sector by gravity mediation. The new D-term contains free parameters that can give large masses to scalar superpartners of quarks and leptons and to the higgsinos while holding the masses of observed particles fixed. Gauginos receive a mass from a non-canonical kinetic term for the vector supermultiplets. We also present a simple argument proving in full generality that the cutoff $Λ$ of effective theories containing new D-terms can never exceed the supersymmetry breaking scale. In our theory, the relation between D-term and the Hubble constant during inflation also implies the universal relation $Λ\lesssim \sqrt{H M_{Pl}}$.

hep-th↗

arXiv2022

Supertranslation-Invariant Dressed Lorentz Charges

We present an explicit formula for Lorentz boosts and rotations that commute with BMS supertranslations in asymptotically flat spacetimes. Key to the construction is the use of infrared regularizations and of a unitary transformation that makes observables commute with the soft degrees of freedom. We explicitly verify that our charges satisfy the Lorentz algebra and we check that they are consistent with expectations by evaluating them on the supertranslated Minkowski space and on the boosted Kerr black hole.

hep-th↗

arXiv2021

Coherent Qubit Measurement in Cavity-Transmon Quantum Systems

A measurement of the time between quantum jumps implies the capability to measure the next jump. During the time between jumps the quantum system is not evolving in a closed or unitary manner. While the wave function maintains phase coherence it evolves according to a non-Hermitian effective Hamiltonian. So under null measurement the timing of the next quantum jump can change by very many orders of magnitude when compared to rates obtained by multiplying lifetimes with occupation probabilities obtained via unitary transformation. The theory developed in 1987 for atomic fluorescence is here extended to transitions in transmon qubits. These systems differ from atoms in that they are read out with a harmonic cavity whose resonance is determined by the state of the qubit. We extend our analysis of atomic fluorescence to this infinite level system by treating the cavity as a quantum system. We find that next photon statistics is highly non exponential and when implemented will enable faster readout, such as on time scales shorter than the decay time of the cavity. Commonly used heterodyne measurements are applied on time scales longer than the cavity lifetime. The overlap between the next photon theory and the theory of heterodyne measurement which are described according to the Stochastic Schroedinger Equation is elucidated. In the limit of large dispersion the intrinsic error for next jump detection -- at short time -- tends to zero. Whereas for short time dyne detection the error remains finite for all values of dispersion.

quant-ph↗

arXiv2021

Component Actions of Liberated $\mathcal{N} = 1$ Supergravity and New Fayet-Iliopoulos Terms in Superconformal Tensor Calculus

We explicitly compute the component action of certain recently discovered new $\mathcal{N} = 1$ supergravity actions which enlarge the space of scalar potentials allowed by supersymmetry and also contain fermionic interaction terms that become singular when supersymmetry is unbroken. They are the "Liberated Supergravity" introduced by Farakos, Kehagias and Riotto, and supergravities with a new Kahler-invariant Fayet-Iliopoulos term proposed by Antoniadis, Chatrabhuti, Isono, and Knoops. This paper is complementary to our previous papers [Phys. Rev. D 103 (2021), 025008 and 105006], in which new constraints on the coupling constants of those new theories were found. In this paper we spell out many details that were left out of our previous papers.

hep-th↗

arXiv2021

Partition Functions of Chern-Simons Theory on Handlebodies by Radial Quantization

We use radial quantization to compute Chern-Simons partition functions on handlebodies of arbitrary genus. The partition function is given by a particular transition amplitude between two states which are defined on the Riemann surfaces that define the (singular) foliation of the handlebody. The final state is a coherent state while on the initial state the holonomy operator has zero eigenvalue. The latter choice encodes the constraint that the gauge fields must be regular everywhere inside the handlebody. By requiring that the only singularities of the gauge field inside the handlebody must be compatible with Wilson loop insertions, we find that the Wilson loop shifts the holonomy of the initial state. Together with an appropriate choice of normalization, this procedure selects a unique state in the Hilbert space obtained from a Kähler quantization of the theory on the constant-radius Riemann surfaces. Radial quantization allows us to find the partition functions of Abelian Chern-Simons theories for handlebodies of arbitrary genus. For non-Abelian compact gauge groups, we show that our method reproduces the known partition function at genus one.

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