In this letter we present a new N-flation model constructed by making use of multiple scalar fields which are being described by their own DBI action. We show that the dependence of the e-folding number and of the curvature perturbation on the number of fields changes compared with the normal N-flation model. Our model is also quite different from the usual DBI N-flation which is still based on one DBI action but involves many moduli components. Some specific examples of our model have been analyzed.
We construct a Dirac-Born-Infeld (DBI) action coupled to a two-form field in four dimensional $\mathcal{N}=1$ supergravity. Our superconformal formulation of the action shows a universal way to construct it in various Poincaré supergravity formulations. We generalize the DBI action to that coupled to matter sector. We also discuss duality transformations of the DBI action, which are useful for phenomenological and cosmological applications.
We develop an action principle to construct the dynamics that give rise to a minimal generalization of Einstein's equations, where the speed of light ($c$), the gravitational constant ($G$) and the cosmological constant ($Λ$) are allowed to vary. Our construction preserves general covariance of the theory, which yields a general dynamical constraint on $c$, $G$ and $Λ$. This action is general and can be applied to describe different cosmological solutions. We apply this formulation to the initial condition puzzles of the early universe and show that it generates a dynamical mechanism to obtain…
We construct the Dirac-Born-Infeld (DBI) action of a real linear multiplet in 4D $\mathcal{N}=1$ supergravity. Based on conformal supergravity, we derive the general condition under which the DBI action can be realized, and show that it can be constructed in the new minimal supergravity. We also generalize it to the matter coupled system.
By explicit calculations of four-field couplings, we observe that the higher derivative corrections to the DBI action in flat space-time, can be either in a covariant form or in a T-duality invariant form. The two forms are related by a non-covariant field redefinition. Using this observation, we then propose a non-covariant but T-duality invariant action which includes all orders of massless fields and has two extra derivatives with respect to the DBI action.
In this paper we study a new class of inflation models which generalize the Dirac-Born-Infeld (DBI) action with the addition of a nonminimal kinetic coupling (NKC) term. We dubbed this model as the {\it new DBI inflation model}. The NKC term does not bring new dynamical degree of freedom, so the equations of motion remain of second order. However, with such a coupling, the action is no longer linear with respect to the Einstein curvature term ($R$ or $G^{μν}$), which leads to a correction term of $k^4$ in the perturbations. The new DBI inflation model can be viewed as theories beyond Horndeski…
The Dirac-Born-Infeld (DBI) field theory in string theory is important and can provide the field of the universe's inflation. At the same time, it provides a causal mechanism for generating the original density perturbation, thereby providing the necessary density perturbation for existing the dense and sparse matter distributions of the universe. However, there is the paradox of the conversion of potential energy and kinetic energy in equal rights in string theory. Therefore, we give a new general DBI action, which enables the kinetic energy and potential energy in the action to be converted …
We use the compatibility of D-brane action with linear off-shell T-duality and linear on-shell S-duality as guiding principles to find all world volume couplings of one massless closed and three massless open strings at order $α'^2$ in type II superstring theories in flat space-time.
The Dirac action describes the physics of the Nambu-Goldstone scalars found on branes. The Born-Infeld action defines a non-linear theory of electrodynamics. The combined Dirac-Born-Infeld (DBI) action describes the leading interactions supported on a single D-brane in string theory. We define a non-abelian analogue of DBI using the $T \overline{T}$ deformation in two dimensions. The resulting quantum theory is compatible with maximal supersymmetry and such theories are quite rare.
It is known that D$_p$-brane effective action at the leading order of $α'$ in flat space-time which is given by DBI action, transforms to D$_{p-1}$-brane effective action under standard T-duality transformations of the open string gauge bosons and transverse scalar fields. Extending this duality to order $α'$, one may find corrections to the DBI action which include the second fundamental form $Ω$ and the covariant derivative of gauge field strength $DF$, as well as the corrections to the T-duality transformations. Using this idea, up to two parameters, we have found all 81 covariant couplings…
We obtain precise temperature dependence of three transport coefficients that resembles strange metal: (a) longitudinal electrical conductivity (b) longitudinal thermoelectric conductivity (c) longitudinal thermal conductivity in the absence of magnetic field. This is achieved through one parameter, namely, when the dynamical exponent, $z=4$. Moreover, in the presence of magnetic field, we have cooked up a model where it exhibits the desired temperature dependence of the four transport quantities that resembles strange metal.
We study a systematic derivation of four dimensional $\mathcal{N}=1$ supersymmetric effective theory from ten dimensional non-Abelian Dirac-Born-Infeld action compactified on a six dimensional torus with magnetic fluxes on the D-branes. We find a new type of matter Kähler metric while gauge kinetic function and superpotential are consistent with previous studies. For the ten dimensional action, we use a symmetrized trace prescription and focus on the bosonic part up to $\mathcal{O}(F^4)$. In the presence of the supersymmetry, four dimensional chiral fermions can be obtained via index theorem. …
Multi-field DBI inflation: introducing bulk forms and revisiting the gravitational wave constraints
我们研究了多场Dirac Born Infeld（DBI）暴胀模型，考虑了NS NS和R-R体场在一般通量紧致化中的存在.我们计算的二阶作用，这支配的线性宇宙学扰动的行为，以及三阶作用，这可以用来计算这些模型中的非高斯性。值得注意的是，对于标量型扰动，我们表明，由于各种形式的字段的贡献完全取消在第二和第三阶的行动。因此，原始扰动和它们的非高斯性不受形式场的影响，我们以前的结果是未修改的。我们还研究了与U（1）规范场有关的矢量型扰动，并讨论了它们的量子涨落是否可以被放大。最后，我们重新审视了引力波对DBI膨胀的约束，并表明与单场情况相比，紫外DBI多场情况仍然与数据兼容，前提是存在从熵到绝热扰动的转移。
We study quantum corrections to hypersurfaces of dimension $d+1>2$ embedded in generic higher-dimensional spacetimes. Manifest covariance is maintained throughout the analysis and our methods are valid for arbitrary co-dimension and arbitrary bulk metric. A variety of theories which are prominent in the modern amplitude literature arise as special limits: the scalar sector of Dirac-Born-Infeld theories and their multi-field variants, as well as generic non-linear sigma models and extensions thereof. Our explicit one-loop results unite the leading corrections of all such models under a single u…
We employ gauge-gravity duality to study the backreaction effect of 4-dimensional large-$N$ quantum field theories on constant-curvature backgrounds, and in particular de Sitter space-time. The field theories considered are holographic QFTs, dual to RG flows between UV and IR CFTs. We compute the holographic QFT contribution to the gravitational effective action for 4d Einstein manifold backgrounds. We find that for a given value of the cosmological constant $λ$, there generically exist two backreacted constant-curvature solutions, as long as $λ< λ_{\textrm{max}} \sim M_p^2 / N^2$, otherwise n…
In string theory compactifications it is common to find an effective Lagrangian for the scalar fields with a non-canonical kinetic term. We study the effective action of the scalar position moduli of Type II D$p$-branes. In many instances the kinetic terms are in fact modified by a term proportional to the scalar potential itself. This can be linked to the appearance of higher-dimensional supersymmetric operators correcting the Kähler potential. We identify the supersymmetric dimension-eight operators describing the $α'$ corrections captured by the D-brane Dirac-Born-Infeld action. Our analysi…
A way to describe the hydrodynamics of the quark-gluon plasma using a DBI action is proposed, based on the model found by Heisenberg for high energy scattering of nucleons. The expanding plasma is described as a shockwave in a DBI model for a real scalar standing in for the pion, and I show that one obtains a fluid description in terms of a relativistic fluid that near the shock is approximately ideal ($η\simeq 0$) and conformal. One can introduce an extra term inside the square root of the DBI action that generates a shear viscosity term in the energy-momentum tensor near the shock, as well a…
We use the DBI action from string theory and holography to study the magneto-resistance at quantum criticality with hyperscaling violation. We find and analyze a rich class of scaling behaviors for the magneto-resistance. A special case describes the scaling results found in pnictides by Hayers et al. in~\cite{analytis}.
Primordial perturbations and non-Gaussianities in DBI and general multi-field inflation
本文研究了具有多个标量场和任意动力学项的一般暴胀模型中的宇宙学扰动，重点研究了Dirac Born Infeld（DBI）暴胀的多场扩展.在最一般的情况下，我们计算的二阶作用的线性扰动的动力学。专门为DBI，我们表明，绝热和熵模式传播的{ \it共同}有效的声速，从而在声音的地平线交叉放大。在小声速极限下，我们发现熵模的振幅比绝热模的振幅大得多。在一般情况下，我们还得到了三阶作用量，这对于研究暴胀过程中产生的原始非高斯性是有用的。在DBI的情况下，我们计算占主导地位的贡献，非高斯性，这取决于绝热和熵模式。
本文研究了弯曲背景下ND 0-膜的作用量。特别是，我们专注于时空同构不变性的意义。对于单个D-膜，超同态不变性以一种朴素的方式作用于世界体积场，但对于多个D-膜，超同态不变性的意义要模糊得多。这个问题超出了确定U（N）-值域的序的范围，因为我们可以证明普通的超同态不能提升为矩阵值超同态。另一方面，作用量可以通过微扰弦论计算来构造。基于这样的计算的一般特性，我们确定了一组约束的行动N D 0膜，确保时空协方差。这些约束可以一个接一个地解决，但它们不足以完全确定动作。约束的所有解都服从D-几何的公理。此外，行动必须包含新的条款。这清楚地表明，答案不仅仅是单个D 0膜的作用的适当排序。
